Combined Cabazitaxel and Carboplatin Treatment of Metastatic Castration Resistant Prostate Cancer Patients, With Innate or Acquired Resistance to Cabazitaxel Monotherapy

BACKGROUND

There is new interest in platinum-based treatment of patients with metastatic castration resistant prostate cancer (mCRPC), to which a subgroup responds. Although platinum sensitivity is suggested to be associated with aggressive disease features and distinct molecular profiles, identification of responders is a clinical challenge. In this study, we selected patients who displayed PSA progression during cabazitaxel monotherapy, for combined cabazitaxel and carboplatin treatment.

METHODS

In this retrospective study, mCRPC patients received carboplatin and cabazitaxel after biochemical progression following at least 2 cabazitaxel monotherapy cycles. We assessed PSA response, Time to PSA Progression (TTpsa) and Time to Radiographic Progression (TTrad). For a subset of patients, mutational analysis of BRCA-1, BRCA-2, ATM, PTEN, P53 and RB1 was performed.

RESULTS

Forty-five patients were included, after a median of 4 (3-6) cycles of cabazitaxel monotherapy. Patients received a median of 3 (2-5) cycles of combined cabazitaxel and carboplatin, on which 12 (26.6%) patients had a PSA decline ≥ 50% from baseline. TTpsa was 2 (1-5) months and TTrad 3 (2-6) months. Adverse events were predominantly grade 1-2. Of the 29 (64.4%) patients evaluable for molecular signature, 6 (13.3%) had BRCA1, BRCA2 or ATM mutations and 12 (26.7%) had a PTEN, P53 or RB1 mutations. The occurrence of these mutations was not associated with any clinical outcome measure.

CONCLUSIONS

In this study we showed that patients with PSA progression during cabazitaxel monotherapy could benefit from the addition of carboplatin to cabazitaxel, while prospective identification of these patients remains a clinical challenge.

Is Higher Docetaxel Clearance in Prostate Cancer Patients Explained by Higher CYP3A? An In Vivo Phenotyping Study with Midazolam

Patients with prostate cancer (PCa) have a lower docetaxel exposure for both intravenous (1.8-fold) and oral administration (2.4-fold) than patients with other solid cancers, which could influence efficacy and toxicity. An altered metabolism by cytochrome P450 3A (CYP3A) due to castration status might explain the observed difference in docetaxel pharmacokinetics. In this in vivo phenotyping, pharmacokinetic study, CYP3A activity defined by midazolam clearance (CL) was compared between patients with PCa and male patients with other solid tumors. All patients with solid tumors who did not use CYP3A-modulating drugs were eligible for participation. Patients received 2 mg midazolam orally and 1 mg midazolam intravenously on 2 consecutive days. Plasma concentrations were measured with a validated liquid chromatography-tandem mass spectrometry method. Genotyping was performed for CYP3A4 and CYP3A5. Nine patients were included in each group. Oral midazolam CL was 1.26-fold higher in patients with PCa compared to patients with other solid tumors (geometric mean [coefficient of variation], 94.1 [33.5%] L/h vs 74.4 [39.1%] L/h, respectively; P = .08). Intravenous midazolam CL did not significantly differ between the 2 groups (P = .93). Moreover, the metabolic ratio of midazolam to 1'-hydroxy midazolam did not differ between the 2 groups for both oral administration (P = .67) and intravenous administration (P = .26). CYP3A4 and CYP3A5 genotypes did not influence midazolam pharmacokinetics. The observed difference in docetaxel pharmacokinetics between both patient groups therefore appears to be explained neither by a difference in midazolam CL nor by a difference in metabolic conversion rate of midazolam.

Patient-reported outcomes (PROs) in KEYNOTE-921: Pembrolizumab (pembro) plus docetaxel for patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

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Background: The double-blind, phase 3, randomized KEYNOTE-921 trial (NCT03834506) showed that pembro + docetaxel did not significantly improve rPFS or OS for pts with mCRPC treated with prior next-generation hormonal agent (NHA) therapy. We present PROs for pembro + docetaxel vs placebo + docetaxel in KEYNOTE-921. Methods: Pts were randomly assigned 1:1 to receive pembro 200 mg or placebo IV Q3W (≤35 cycles) + docetaxel 75 mg/m2 IV Q3W (≤10 cycles) and prednisone 5 mg orally BID. PROs were evaluated in pts who received ≥1 dose of study treatment and had ≥1 PRO assessment. FACT-P and BPI-SF were administered at baseline, Q3W until wk 24, Q6W until wk 72, then Q12W for ≤2 y. A prespecified secondary end point was time to pain progression (TTPP) based on BPI-SF. Prespecified exploratory end points included least squares mean (LSM) change from baseline to wk 27 for FACT-P total and subscale scores (FACT-G total, TOI, FAPSI-6, FWB, PWB, and PCS) and wk 24 for BPI-SF scores (pain interference, pain severity, and worst pain), and time to deterioration (TTD) and overall improvement rate in FACT-P total and subscale scores. Differences were evaluated using 2-sided nominal P values not controlled for multiplicity. Results: Of 1030 pts enrolled, the PRO analysis population included 1028 (n = 514 in each arm). At the prespecified final analysis, median time from randomization to data cutoff of June 20, 2022, was 22.7 mo (range, 12.1-36.7). Completion rates for FACT-P and BPI-SF were >78% at baseline, >65% for FACT-P at wk 27, and >63% for BPI-SF at wk 24. Median TTPP was 21.1 mo (95% CI, 13.7-NR) for pembro + docetaxel vs NR (95% CI, 13.8-NR) for placebo + docetaxel (HR, 1.05 [95% CI, 0.77-1.43]). No LSM differences were observed in FACT-P total scores with pembro + docetaxel (–5.31 [95% CI, –7.02 to –3.61]) vs placebo + docetaxel (–3.89 [95% CI, –5.59 to –2.19]) or BPI-SF scores. Median TTD in FACT-P total scores was 21.8 mo (95% CI, 20.0-NR) for pembro + docetaxel and NR (95% CI, 11.1-NR) for placebo + docetaxel (HR, 1.09 [95% CI, 0.88-1.35]). No differences were observed for TTD in FACT-G total, TOI, FAPSI-6, FWB, PWB, and PCS scores between groups. A numerically lower proportion of pts receiving pembro + docetaxel (39.9%) had improved + stable FACT-P total scores compared with placebo + docetaxel (45.3%). FACT-P and BPI-SF scores were generally maintained across all evaluated time points up to wk 81. Conclusions: HRQoL and disease-related symptom scores at all analyzed time points, as well as TTD and TTPP, were similar between the 2 trial arms. These data suggest that pembro + docetaxel did not negatively impact QoL in pts with mCRPC treated with prior NHA. Clinical trial information: NCT03834506 . [Table: see text]

Activity of lutetium-177 PSMA (Lu-PSMA) and determinants of outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with cabazitaxel: The PACAP study

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Background: Cabazitaxel and Lu-PSMA both improved survival in patients with mCRPC after docetaxel and an androgen receptor pathway inhibitor (ARPI), but there is limited data regarding Lu-PSMA activity after cabazitaxel. We aimed at assessing activity of Lu-PSMA and determinants of outcomes in this setting. Methods: Consecutive mCRPC patients from 6 European centers treated with Lu-PSMA after cabazitaxel were included in this retrospective study. Endpoints included radiographic progression-free survival (rPFS), time to PSA progression (PSA-TTP), PSA decline, objective response, overall survival, and safety. Results: Of 101 patients included (median age 67y), 64% had ISUP grade 4-5 disease; 71% had bone +/- nodal (LN) metastases, 22% visceral metastases, 7% LN only. All patients and 92% had received previous docetaxel and a prior ARPI (≥ 2 in 47%) before cabazitaxel respectively. Patients had received a median number of 6 cabazitaxel cycles (range 1-26). DNA damage repair alterations (DDR) were found in 11/48 (23%) patients with available testing. Patients received a median number of 3 Lu-PSMA cycles (range 1-14). With a median follow-up of 5.7 months, the median rPFS from Lu-PSMA initiation was 4.3 months (m, 95%CI 3.2-5.7) and median PSA-TTP was 3.5 m (95%CI 3.0-4.5). Overall, 44 patients (44%) experienced a PSA decline ≥ 50% (PSA50), 54 (53%) ≥ 30% (PSA30), and 67 (66%) any PSA decline. Objective response rate was 34%. Baseline characteristics associated with shorter rPFS on Lu-PSMA included ISUP grade 4-5 disease (median rPFS of 3.5 vs. 7.2m, p=0.02) and a time to castration resistance < 12 months (3.1m vs. 4.5m, p=0.04). Patients with LN only had longer rPFS compared to those with bone and visceral metastases (median NR vs. 3.6 and 3.7m, respectively, p=0.02). There was no association between activity of Lu-PSMA and DNA damage repair alterations, duration of previous cabazitaxel therapy, and number of previous ARPI. During Lu-PSMA, a profound PSA decline was associated with longer rPFS: patients achieving PSA50, PSA30 or any PSA decline had respective median rPFS rates of 9.0, 8.3 and 6.2 months, while those who did not experience any PSA decline had a median rPFS of only 2.6 months. Conclusions: Lu-PSMA demonstrated substantial PSA decline but limited duration of response after cabazitaxel in a real-life setting. Adverse baseline characteristics and absence of PSA decline may help early identification of poor responders.

Pembrolizumab plus docetaxel for patients with metastatic castration-resistant prostate cancer (mCRPC): Randomized, double-blind, phase 3 KEYNOTE-921 study

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Background: Docetaxel is a treatment option following disease progression on a next-generation hormonal agent (NHA) for patients with mCRPC, but there is an urgent need for more efficacious treatments. The randomized, double-blind, phase 3 KEYNOTE-921 study (NCT03834506) evaluated the efficacy and safety of pembrolizumab + docetaxel vs placebo + docetaxel for participants (pts) with mCRPC who had received prior NHA therapy. Methods: Eligible pts were ≥18 years old, had mCRPC that progressed on androgen deprivation therapy, had received 1 prior NHA, and had an ECOG performance status of 0 or 1. Pts were randomized 1:1 to receive 200 mg pembrolizumab Q3W or placebo for ≤35 cycles (~2 years) in combination with 75 mg/m2 docetaxel Q3W for ≤10 cycles and 5 mg prednisone BID. The dual primary endpoints were radiographic progression-free survival (rPFS; tested at first interim analysis) per PCWG-modified RECIST 1.1 by blinded independent central review and overall survival (OS; tested at final analysis). The key secondary endpoint was time to initiation of the first subsequent anticancer therapy (TFST; at first interim analysis). Safety was one of the secondary endpoints. Results: Between May 30, 2019 and June 17, 2021, 1030 pts were randomized to receive pembrolizumab + docetaxel (n=515) or placebo + docetaxel (n=515). The median (range) time from randomization to data cutoff date of June 20, 2022 at final analysis was 22.7 mo (12.1−36.7). Baseline characteristics were generally balanced between arms; approximately half of pts in each arm had received prior abiraterone. Pts in the pembrolizumab + docetaxel arm received a median (range) of 12 (1–35) cycles of pembrolizumab and 9 (1–12) cycles of docetaxel; pts in the placebo + docetaxel arm received a median (range) of 12 (1–35) cycles of placebo and 9 (1–10) cycles of docetaxel. The dual primary endpoints of rPFS (median 8.6 mo with pembrolizumab + docetaxel vs 8.3 mo with placebo + docetaxel; HR 0.85, 95% CI 0.71−1.01; P=0.0335) and OS (median 19.6 mo vs 19.0 mo; HR 0.92, 95% CI 0.78−1.09; P=0.1677) were not met. Median TFST was 10.7 mo vs 10.4 mo, respectively (HR 0.86, 95% CI 0.74−1.01). Treatment-related AEs occurred in 94.6% (grade ≥3 in 43.2%) and 94.9% (grade ≥3 in 36.6%) of pts with pembrolizumab + docetaxel vs placebo + docetaxel. 2 treatment-related deaths with pembrolizumab + docetaxel and 7 with placebo + docetaxel were reported. Immune-mediated AEs and infusion reactions occurred in 23.3% (grade ≥3 in 6.2%) and 12.3% (grade ≥3 in 1.2%) of pts with pembrolizumab + docetaxel vs placebo + docetaxel, most commonly pneumonitis (7.0% vs 3.1%) and hypothyroidism (6.4% vs 3.3%). Conclusions: The addition of pembrolizumab to docetaxel did not significantly improve rPFS or OS for pts with mCRPC and did not result in a notable increase in treatment-related AEs. Clinical trial information: NCT03834506 .

Predictors of early polymetastatic relapse following stereotactic ablative radiotherapy for up to 5 oligometastases: a secondary analysis of the phase II SABR-5 trial

PURPOSE

A subset of patients with oligometastatic cancer experience early widespread cancer dissemination and do not benefit from metastasis-directed therapy such as stereotactic ablative radiotherapy (SABR). This study aimed to identify factors associated with early polymetastatic relapse (PMR).

METHODS AND MATERIALS

The XXX trial was a single arm phase II study conducted at all 6 regional cancer centres across XXX. SABR for oligometastases was only offered on trial. Patients with up to 5 oligometastatic lesions (total, progressing or induced) received SABR to all lesions. Patients were 18 years of age or older, ECOG 0-2 and life expectancy ≥ 6 months. This secondary analysis evaluated factors associated with early PMR, defined as disease recurrence within 6 months of SABR which is not amenable to further local treatment. Univariable and multivariable analyses were performed using binary logistic regression. The Kaplan Meier method and log-rank tests assessed PMR-free survival and differences between risk groups, respectively.

RESULTS

Between November 2016 and July 2020, 381 patients underwent treatment on XXX. A total of 16% of patients experienced PMR. Worse performance status (ECOG 1-2 vs 0; HR=2.01, p=0.018), non-prostate/breast histology (HR=3.64, p<0.001) and oligoprogression (HR=3.84, p<0.001) were independent predictors for early PMR. Risk groups were identified with median PMR-free survival ranging from 5 months to not yet reached at the time of analysis. Rates of 3-year OS were 0%, 53% (95% confidence interval [CI] 48 - 58), 77% (95% CI 73 - 81) and 93% (95% CI 90 - 96) in groups 1-4, respectively (p<0.001).

CONCLUSION

Four distinct risk groups for early PMR are identified, which differ significantly in PMR-free survival and overall survival. The group with all three risk factors had a median PMR-free survival of 5 months and may not benefit from local ablative therapy alone. This model should be externally validated with data from other prospective trials.

Progression-free survival and local control following stereotactic ablative radiotherapy for up to 5 oligometastases: an analysis from the population-based phase II SABR-5 trial

PURPOSE

Despite increasing utilization of stereotactic ablative therapy (SABR) for oligometastatic cancer, prospective outcomes are lacking. The purpose of this study was to determine progression-free survival (PFS), local control (LC) and prognostic factors from the population-based phase II XXX trial.

METHODS AND MATERIALS

The XXX trial was a single arm phase II study with the primary endpoint of toxicity, conducted at the 6 regional cancer centres across XXX, during which time SABR for oligometastases was only offered on trial. Patients with up to 5 oligometastases (total or not controlled by prior treatment, and including induced oligometastatic disease) underwent SABR to all lesions. Patients were 18 years of age or older, ECOG 0-2 and had life expectancy ≥ 6 months. The secondary outcomes of PFS and LC are presented here.

RESULTS

Between November 2016 and July 2020, 381 patients underwent SABR on trial. Median follow-up was 27 months (IQR 18-36). Median PFS was 15 months (95% CI 12-18). LC at 1 and 3 years were 93% (95% CI 91 - 95) and 87% (95% CI 84 - 90), respectively. On multivariable analysis, increasing tumor diameter (HR=1.09, p<0.001), declining performance status (HR=2.13, p<0.001), disease-free interval < 18 months (HR=1.52, p=0.003), four or more metastases at SABR (HR=1.48, p=0.048), initiation or change in systemic treatment (HR=0.50, p<0.001) and oligoprogression (HR=1.56, p=0.008) were significant independent predictors of PFS. Tumor diameter (SHR=1.28, p<0.001), colorectal histology (SHR=4.33, p=0.002) and "other" histology (SHR=3.90, p<0.001) were associated with worse local control.

CONCLUSIONS

In this population-based cohort including patients with genuine oligometastatic, oligoprogressive, and induced oligometastatic disease, the median PFS was 15 months and LC at 3 years was 87%. This supports ongoing efforts to randomize patients on phase III trials, even outside the original 1-5 metachronous oligometastatic paradigm.

Symptomatic Skeletal Events and the Use of Bone Health Agents in a Real-World Treated Metastatic Castration Resistant Prostate Cancer Population: Results From the CAPRI-Study in the Netherlands

BACKGROUND

Patients with metastatic castration resistant prostate cancer (mCRPC) are at risk of symptomatic skeletal events (SSE). Bone health agents (BHA, ie bisphosphonates and denosumab) and new life-prolonging drugs (LPDs) can delay SSEs. The aim of this study is to investigate the use of BHAs in relation to SSEs in treated real-world mCRPC population.

PATIENTS AND METHODS

We included patients from the CAPRI registry who were treated with at least one LPD and diagnosed with bone metastases prior to the start of first LPD (LPD1). Outcomes were SSEs (external beam radiation therapy (EBRT) to the bone, orthopedic surgery, pathologic fracture or spinal cord compression) and SSE-free survival (SSE-FS) since LPD1.

RESULTS

One-thousand nine hundred and twenty-three patients were included with a median follow-up from LPD1 of 16.7 months. Fifty-two percent (n = 996) started BHA prior or within 4 weeks after the start of LPD1 (early BHA). In total, 41% experienced at least one SSE. SSE incidence rate was 0.29 per patient year for patients without BHA and 0.27 for patients with early BHA. Median SSE-FS from LPD1 was 12.9 months. SSE-FS was longer in patients who started BHA early versus patients without BHA (13.2 vs. 11.0 months, P = .001).

CONCLUSION

In a real-world population we observed an undertreatment with BHAs, although patients with early BHA use had lower incidence rates of SSEs and longer SSE-FS. This finding was irrespective of type of SSE and presence of risk factors. In addition to LPD treatment, timely initiation of BHAs is recommended in bone metastatic CRPC-patients with both pain and/or opioid use and prior SSE.

High-Intensity Care in the End-of-Life Phase of Castration-Resistant Prostate Cancer Patients: Results from the Dutch CAPRI-Registry

Background: Intensive end-of-life care (i.e., the overuse of treatments and hospital resources in the last months of life), is undesirable since it has a minimal clinical benefit with a substantial financial burden. The aim was to investigate the care in the last three months of life (end-of-life [EOL]) in castration-resistant prostate cancer (CRPC). Methods: Castration-resistant prostate cancer registry (CAPRI) is an investigator-initiated, observational multicenter cohort study in 20 hospitals retrospectively including patients diagnosed with CRPC between 2010 and 2016. High-intensity care was defined as the initiation of life-prolonging drugs (LPDs) in the last month, continuation of LPD in last 14 days, >1 admission, admission duration ≥14 days, and/or intensive care admission in last three months of life. Descriptive and binary logistic regression analyses were performed. Results: High-intensity care was experienced by 41% of 2429 patients in the EOL period. Multivariable analysis showed that age (odds ratio [OR] 0.98, 95% confidence interval [CI] 0.97-0.99), performance status (OR 0.57, 95% CI 0.33-0.97), time from CRPC to EOL (OR 0.98, 95% CI 0.97-0.98), referral to a medical oncologist (OR 1.99, 95% CI 1.55-2.55), prior LPD treatment (>1 line OR 1.72, 95% CI 1.31-2.28), and opioid use (OR 1.45, 95% CI 1.08-1.95) were significantly associated with high-intensity care. Conclusions: High-intensity care in EOL is not easily justifiable due to high economic cost and little effect on life span, but further research is awaited to give insight in the effect on patients' and their caregivers' quality of life.

First results from a randomized phase II study of cabazitaxel (CBZ) versus an androgen receptor targeted agent (ARTA) in patients with poor-prognosis castration-resistant prostate cancer (mCRPC)

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Background: In the OSTRICh trial, poor-prognosis mCRPC patients were randomized between CBZ and ARTA, following progression on docetaxel (DOC) treatment. Methods: The OSTRICh trial is an open label, multicenter, phase IIb study. Patients with poor-prognosis mCRPC (visceral metastases AND/OR < 12 months responsive to androgen deprivation AND/OR progressing during or within 6 months after DOC completion), were randomized 1:1 between CBZ (25 mg/m2 IV Q3W and prednisone 2 d 5 mg PO) and ARTA (daily abiraterone 1000 mg and prednisone 2 d 5 mg PO OR enzalutamide 160 mg PO). Life prolonging therapy between DOC and randomization was not allowed. Primary endpoint was to establish the Clinical Benefit Rate (no radiotherapy, no ECOG PS increase ≥2, no change of therapy AND no radiological progression) at 12 weeks (CBR) in the study arms, while formal comparison of the CBR was a secondary endpoint. A Fisher Exact test was used to assess differences in rates and a log rank test to assess differences in progression free and overall survival. All time to event endpoints were estimated with the Kaplan-Meier method and censored at last follow-up. Results: A total of 106 patients were randomized, 53 in each arm. Baseline median age was 70 (IQR 67-75) years and PSA 79.4 (IQR 29.0 - 160) ng/ml. ECOG PS score was 0/1 in 99 (93%) and 2 in 7 (7%) patients. Al patients fulfilled the criteria for poor-prognosis disease. Thirty-six (34%) patients received DOC in the metastatic hormone sensitive stage, while 41 (39%) previously received ARTA. Twenty-six of 43 evaluable patients in the CBZ arm had clinical benefit at 12 weeks (CBR: 60%, 95% CI: 44%-75%) and 20 of 39 (CBR: 51%, 95% CI: 35%-68%) in the ARTA arm (p = 0.50). At 12 weeks, 30 of 34 (88%, 95% CI: 73% - 97%) patients in the CBZ arm and 24 of 36 (67%, 95% CI: 49% - 81%) patients in the ARTA arm had no radiological progression (p = 0.046). After a median follow-up of 16.4 months (95% CI: 13.6–27.8), a serum PSA decrease ≥50% from baseline was established in 12 (23%, 95% CI: 12% - 36%) and 26 (49%, 95% CI: 35% - 63%)(p = 0.008) patients treated with CBZ and ARTA, respectively. Median radiological progression free survival (rPFS) was 6.0 months (95%CI: 4.11-14.5) in the CBZ arm and 5.8 months (95% CI: 5.22-10.2) months in the ARTA arm (p = 0.5), while median overall survival (OS) was 15.3 months (95%CI 9.49-22.4) and 13.8 months (95%CI 11.7-16.4) in CBZ and ARTA treated patients, respectively (p = 0.8). Grade ≥3 adverse events (AEs) occurred in 15 (29%) and 8 (15%) of patients treated with CBZ and ARTA, respectively. Conclusions: No significant difference in CBR was established between CBZ and ARTA treated patients. However, at 12 weeks significantly more CBZ treated patients had no radiological progression, while ≥50% PSA response rates were higher in ARTA treated patients. Clinical trial information: NCT03295565.

Cortisol as biomarker for CYP17 inhibition in mCRPC patients treated with abiraterone acetate

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Background: Abiraterone acetate is an effective metastatic castration resistant prostate cancer (mCRPC) treatment, however, there is a high variability in response. It inhibits CYP17, thereby preventing the production of androgens. Abiraterone trough concentrations (Cmin) > 8.4 ng/mL have been associated with an increased progression free survival (PFS) (Eur J Cancer. 2017;72:54-61; Prostate Cancer Prostatic Dis. 2020;23(2):244-251). However, plasma levels do not directly provide information on the level of CYP17 inhibition. Ideally, testosterone levels should be measured, but these levels are below the detection limit of available assays. The synthesis of cortisol is also inhibited by abiraterone via CYP17 inhibition and might therefore be a biomarker for CYP17 inhibition. The objective of this study was to investigate if cortisol levels are related to abiraterone levels and to clinical response. Methods: An observational study was performed in mCRPC patients treated with abiraterone acetate. At the outpatient clinic, plasma samples were collected for pharmacokinetic (PK) monitoring at each hospital visit. Reference populations of healthy volunteers and mCRPC patients using enzalutamide were included to investigate the influence of mCRPC and abiraterone treatment on the circadian rhythm of cortisol. Abiraterone and cortisol levels were measured using validated liquid chromatography-mass spectrometry (LC-MS/MS) assays. Clinical (prostate specific antigen (PSA) independent) PFS and PSA response were evaluated. Results: In total, 117 mCRPC patients using abiraterone acetate, 100 mCRPC patients using enzalutamide and 12 healthy volunteers were included. A clear circadian rhythm of cortisol was described in healthy volunteers and unaffected in mCRPC patients using enzalutamide. Contrarily, a circadian rhythm of cortisol could not be identified in mCRPC patients using abiraterone acetate, due to continuous suppression throughout the day. Patients with an abiraterone Cmin > 8.4 ng/mL (n = 77) had a median cortisol concentration of 1.03 ng/mL vs. 2.59 ng/mL in patients with an abiraterone Cmin ≤8.4 ng/mL (n = 40) (p = 0.020). The median cortisol concentration in PSA responders (n = 63) was 1.02 ng/mL vs. 2.59 ng/mL for PSA non responders (n = 54) (p = 0.037). Patients in the highest cortisol tertile ( > 3.03 ng/mL) had a median PFS of 3.7 months (n = 39) vs. 13.8 months in patients with cortisol levels ≤3.03 ng/mL (n = 78) (p = 0.007). The median PFS was 16.3 months in patients with an abiraterone Cmin > 8.4 ng/mL and cortisol concentration < 3.03 ng/ml vs. 5.3 months in patients with an abiraterone Cmin > 8.4 ng/mL and cortisol concentration > 3.03 ng/ml (p = 0.02). Conclusions: This study demonstrates that cortisol levels are of additional value to abiraterone concentrations as a marker for abiraterone acetate efficacy. This might help be helpful to assess efficacy of abiraterone treatment.

ModraDoc006, an oral docetaxel formulation in combination with ritonavir (ModraDoc006/r), in metastasized castration-resistant prostate cancer (mCRPC): A multicenter phase I study

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Background: ModraDoc006 is a novel formulation of docetaxel and to enhance bioavailability, this tablet is co-administered with ritonavir (r), an inhibitor of cytochrome p450 3A4 and P-glycoprotein. The safety, anti-tumor activity and pharmacokinetics (PK) of ModraDoc006/r were investigated by dose-escalation in patients with mCRPC, to propose a recommended phase 2 dose (RP2D). Methods: Progressive mCRPC patients, who were treatment naïve or previously treated with either abiraterone or enzalutamide, received a maximum of 30 weekly cycles of ModraDoc006/r in a bi-daily once weekly (BIDW) schedule. Plasma docetaxel concentrations were determined at the first 2 cycles up to 48h after intake of ModraDoc006/r. Adverse events were evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03. Serum Prostate Specific Antigen (PSA) levels were assessed every 6 weeks. Results: 23 patients were included, of whom 20 were evaluable for safety and PK. In 5 patients, the initial 30-20/100-100 dose was explored, with observation of one dose limiting toxicity (DLT) (grade 3 alanine aminotransferase increase). The next dose level of 30-20/200-200 resulted in 2 DLTs in 6 patients (grade 3 diarrhea and mucositis). Subsequently, two intermediate dose levels: 30-20/200-100 and 20-20/200-100 were explored in 6 and 3 patients. At the 30-20/200-100 dose, an adequate docetaxel exposure was achieved and 1 DLT (grade 3 diarrhea) was observed, with no DLTs at the 20-20/200-100 dose. Common treatment-related AEs (occurring in > 30% of all patients) were diarrhea, nausea, vomiting, anorexia and fatigue. Five patients completed the maximum of 30 weekly treatments. In 10 patients, evaluable for anti-tumor activity after treatment with ≥9 cycles, 4 confirmed and 2 non-confirmed PSA responses ( > 50% decrease) were observed. Conclusions: The RP2D of BIDW ModraDoc006/r in mCRPC was established as 30-20/200-100 mg. These results are encouraging for further development of ModraDoc006/r as a convenient, safe and effective alternative to IV docetaxel for mCRPC patients. A phase 2b study is currently being conducted. Clinical trial information: NCT03136640.

Real-world Outcomes of Sequential Androgen-receptor Targeting Therapies with or Without Interposed Life-prolonging Drugs in Metastatic Castration-resistant Prostate Cancer: Results from the Dutch Castration-resistant Prostate Cancer Registry

BACKGROUND

Cross resistance between androgen-receptor targeting therapies (ARTs) (abiraterone acetate plus prednisone [ABI+P] or enzalutamide [ENZ]) for treatment of metastatic castration-resistant prostate cancer (mCRPC) may affect responses to second ART (ART2).

OBJECTIVE

To establish treatment duration and prostate-specific antigen (PSA) response of ART2 in real-world mCRPC patients treated with or without other life-prolonging drugs (LPDs; ie, docetaxel, cabazitaxel, or radium-223) between ART1 and ART2.

DESIGN, SETTING, AND PARTICIPANTS

Castration-resistant prostate cancer patients, diagnosed between 2010 and 2016 were retrospectively registered in Castration-resistant Prostate Cancer Registry (CAPRI). Patients treated with both ARTs were clustered into two subgroups: ART1>ART2 or ART1>LPD>ART2.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Outcomes were ≥50% PSA response and treatment duration of ART2. Descriptive statistics and binary logistic regression after multiple imputations were performed.

RESULTS AND LIMITATIONS

A total of 273 patients were included with a median follow-up of 8.4 mo from ART2. Patients with ART1>ART2 were older and had favourable prognostic characteristics at ART2 baseline compared with patients with ART1>LPD>ART2. No differences between ART1>ART2 and ART1>LPD>ART2 were found in PSA response and treatment duration. Multivariate analysis suggested that PSA response of ART2 was less likely in patients with visceral metastases (odds ratio [OR] 0.143, p=0.04) and more likely in patients with a relatively longer duration of androgen-deprivation treatment (OR 1.028, p=0.01) and with ABI + P before ENZ (OR 3.192, p=0.02). A major limitation of this study was missing data, a common problem in retrospective observational research.

CONCLUSIONS

The effect of ART2 seems to be low, with a low PSA response rate and a short treatment duration irrespective of interposed chemotherapy or radium-223, especially in patients with short time on castration, visceral disease, and ENZ before ABI+P.

PATIENT SUMMARY

We observed no differences in outcomes of patients treated with sequential abiraterone acetate plus prednisone (ABI+P) and enzalutamide (ENZ) with or without interposed chemotherapy or radium-223. In general, outcomes were lower than those in randomised trials, questioning the additional effect of second treatment with ABI+P or ENZ in daily practice.

Second-Line Cabazitaxel Treatment in Castration-Resistant Prostate Cancer Clinical Trials Compared to Standard of Care in CAPRI: Observational Study in the Netherlands

BACKGROUND

Cabazitaxel has been shown to improve overall survival (OS) in metastatic castration-resistant prostate cancer (mCRPC) patients after docetaxel in the TROPIC trial. However, trial populations may not reflect the real-world population. We compared patient characteristics and outcomes of cabazitaxel within and outside trials (standard of care, SOC).

PATIENTS AND METHODS

mCRPC patients treated with cabazitaxel directly after docetaxel therapy before 2017 were retrospectively identified and followed to 2018. Patients were grouped on the basis of treatment within a trial or SOC. Outcomes included OS and prostate-specific antigen (PSA) response.

RESULTS

From 3616 patients in the CAPRI registry, we identified 356 patients treated with cabazitaxel, with 173 patients treated in the second line. Trial patients had favorable prognostic factors: fewer symptoms, less visceral disease, lower lactate dehydrogenase, higher hemoglobin, more docetaxel cycles, and longer treatment-free interval since docetaxel therapy. PSA response (≥ 50% decline) was 28 versus 12%, respectively (P = .209). Median OS was 13.6 versus 9.6 months for trial and SOC subgroups, respectively (hazard ratio = 0.73, P = .067). After correction for prognostic factors, there was no difference in survival (hazard ratio = 1.00, P = .999). Longer duration of androgen deprivation therapy treatment, lower lactate dehydrogenase, and lower PSA were associated with longer OS; visceral disease had a trend for shorter OS.

CONCLUSION

Patients treated with cabazitaxel in trials were fitter and showed outcomes comparable to registration trials. Conversely, those treated in daily practice showed features of more aggressive disease and worse outcome. This underlines the importance of adequate estimation of trial eligibility and health status of mCRPC patients in daily practice to ensure optimal outcomes.

Concomitant intake of abiraterone and food to increase pharmacokinetic exposure: Real-life data from a therapeutic drug monitoring program

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Background: Abiraterone acetate is registered for the treatment of metastatic castration resistant prostate cancer. Pharmacokinetic (PK) exposure has been linked to efficacy, since patients with Cmin ≥ 8.4 ng/mL have a significantly longer progression free survival compared to patients with a Cmin below this threshold (7.4 vs. 12.2 months, p = 0.044) (Carton, 2017). At the recommended fixed dose of 1000 mg QD administered in a modified fasting state, 35% of patients do not reach this efficacy threshold (Carton, 2017), providing a strong rationale for therapeutic drug monitoring (TDM). Since a clinically relevant food effect has been established, concomitant intake of abiraterone and food could offer a cost-neutral solution in case of low exposure (Chi, 2015). This study aims to evaluate whether PK-guided abiraterone dosing is feasible and results in an increased proportion of patients with concentrations above the target. Methods: Patients starting regular treatment with abiraterone were included. PK sampling occurred 4, 8 and 12 weeks after start of treatment, and every 12 weeks thereafter. Abiraterone concentrations were measured and Cmin was calculated. In case of Cmin < 8.4 ng/mL and acceptable toxicity, a PK-guided intervention was advised. As a first step, concomitant intake of abiraterone and a light meal or a snack was advised. Results: In total, 35 patients were included, of which 18 patients (51%) had at least one Cmin < 8.4 ng/mL. These patients were advised to take abiraterone concomitantly with food, after which Cmin increased significantly from 5.6 (47%) ng/mL [mean (CV%)] to 40.6 (110%) ng/mL (p = 0.006) without additional toxicities. This intervention led to adequate exposure in 15 patients (83%). Seventeen patients had all Cmin levels ≥ 8.4 ng/mL, in these patients mean Cmin was 31.5 (65%) ng/mL. Conclusions: TDM of abiraterone was applied in clinical practice and proved to be feasible. Concomitant intake with food resulted into a significant increase in Cmin and offers a cost-neutral opportunity to optimize treatment for patients with low PK exposure. Up to 100 patients will be included to evaluate the effect of PK-guided abiraterone dosing on treatment efficacy. Clinical trial information: NL6695.

Clinical outcomes of a Dutch prospective observational registry of metastatic castration resistant prostate cancer (mCRPC) patients treated with radium-223 (Ra-223)

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Background: In 2012 the ALSYMPCA study established a 3.6 month Overall Survival (OS) benefit of mCRPC patients treated with Ra-223 over placebo. To date clinical outcomes of Ra-223 treatment in a non-study population have not been prospectively evaluated. Methods: The ROTOR registry aimed to include 300 patients in 20 Dutch hospitals prior to Ra-223 treatment at the physician’s discretion. Clinical parameters collected included: positioning of Ra-223, Adverse Events (AE’s; CTCAE v4.03), Skeletal Related Events (SRE) and survival data. SRE was defined as radiotherapy to a bone metastasis, a new pathological fracture, spinal cord compression and/or bone surgery. Progression-Free Survival (PFS) was defined as survival until radiological or clinical progression, subsequent treatment or death. Results: Between April 2014 and September 2017, 305 patients were included of whom 300 were evaluable. The mean age of patients was 72.6 (range 46.3-91.5) years, 255 (85%) had ≥ 6 bone metastases and 197 (65.5%) were pretreated with taxanes and/or abiraterone or enzalutamide (214 (71.3%)). Two-hundred and ninety (96.7%) patients were treated with Ra-223. Twenty-nine (9.7%), 104 (34.7%), 96 (32%) and 66 (22%) patients received Ra-223 as a first, second, third, ≥ fourth mCRPC treatment line, respectively. Patients received an average of 4.6 (SD 1.8) cycles of Ra-223, while 140 (46.7%) completed all six cycles. After a median follow-up of 13.2 months, PFS was 5.1 (CI 4.5-5.8) months and OS 15.2 (CI 12.8-17.6) months. Eighty-two (27.3%) patients were hospitalized during Ra-223 treatment (Serious AE). Grade ≥ 3 anemia, neutropenia and thrombocytopenia was found in 54 (18.0%), 8 (2.7%) and 11 (3.7%) patients, respectively. Other frequent AE’s (all grades) were nausea (90 (30%)), diarrhea (83 (27.7%)) and fatigue (178 (59.3%)). SREs were observed in 46 (15.3%) patients; 22 (7.3%) received radiotherapy, 6 (2%) developed pathologic fractures, 17 (5.6%) spinal cord compression and 1 (0.3%) received bone surgery during Ra-223 therapy. Conclusions: The non-study ROTOR population had characteristics, all grade AEs and OS comparable with the treatment arm of ALSYMPCA. Clinical trial information: NCT03223597.

Neutropenia and docetaxel exposure in metastatic castration-resistant prostate cancer patients: A meta-analysis and evaluation of a clinical cohort

The incidence of neutropenia in metastatic castration‐resistant prostate cancer (mCRPC) patients treated with docetaxel has been reported to be lower compared to patients with other solid tumors treated with a similar dose. It is suggested that this is due to increased clearance of docetaxel in mCRPC patients, resulting in decreased exposure. The aims of this study were to (1) determine if exposure in mCRPC patients is lower vs patients with other solid tumors by conducting a meta‐analysis, (2) evaluate the incidence of neutropenia in patients with mCRPC vs other solid tumors in a clinical cohort, and (3) discuss potential clinical consequences. A meta‐analysis was conducted of studies which reported areas under the plasma concentration‐time curves (AUCs) of docetaxel and variability. In addition, grade 3/4 neutropenia was evaluated using logistic regression in a cohort of patients treated with docetaxel. The meta‐analysis included 36 cohorts from 26 trials (n = 1150 patients), and showed that patients with mCRPC had a significantly lower mean AUC vs patients with other solid tumors (fold change [95% confidence interval (CI)]: 1.8 [1.5‐2.2]), with corresponding AUCs of 1.82 and 3.30 mg∙h/L, respectively. Logistic regression, including 812 patient, demonstrated that patients with mCRPC had a 2.2‐fold lower odds of developing grade 3/4 neutropenia compared to patients with other solid tumors (odds ratio [95%CI]: 0.46 [0.31‐0.90]). These findings indicate that mCRPC patients have a lower risk of experiencing severe neutropenia, possibly attributable to lower systemic exposure to docetaxel.

Androgen receptor moonlighting in the prostate cancer microenvironment

Androgen receptor (AR) signaling is vital for the normal development of the prostate and is critically involved in prostate cancer (PCa). AR is not only found in epithelial prostate cells but is also expressed in various cells in the PCa-associated stroma, which constitute the tumor microenvironment (TME). In the TME, AR is expressed in fibroblasts, macrophages, lymphocytes and neutrophils. AR expression in the TME was shown to be decreased in higher-grade and metastatic PCa, suggesting that stromal AR plays a protective role against PCa progression. With that, the functionality of AR in stromal cells appears to deviate from the receptor's classical function as described in PCa cells. However, the biological action of AR in these cells and its effect on cancer progression remains to be fully understood. Here, we systematically review the pathological, genomic and biological literature on AR actions in various subsets of prostate stromal cells and aim to better understand the consequences of AR signaling in the TME in relation to PCa development and progression.

Combination of carboplatin (AUC4) and cabazitaxel (25 mg/m2) in mCRPC patients not or no longer responding to cabazitaxel monotherapy

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Background: Cabazitaxel monotherapy is a second line treatment option for mCRPC patients. However, not all patients have a PSA response on this treatment, while a proportion of patients develop resistance during cabazitaxel treatment. Platinum drugs might be effective in poorly differentiated disease. Ongoing trials suggest effectivity of the combination in mCRPC, however, thus far clinical parameters cannot predict a response. Therefore, we investigated the addition of carboplatin to cabazitaxel in mCRPC patients who do not have a psa response on cabazitaxel monotherapy or have a PSA rise during treatment. Methods: 19 patients (WHO PS ≤2) who were not responding to ≥2 cycles cabazitaxel monotherapy (25 mg/m2) or two rises of PSA during cabazitaxel were included in this prospective cohort study. All patients received the combination of carboplatin (AUC 4) and cabazitaxel (25 mg/m2). Previous therapies, PSA response, WHO performance score, Progression Free Survival (PFS), Overall Survival (OS) and adverse events were monitored. Results: Median age was 66.7 years, 21% of patients had a WHO PS of 2, 68% had a Gleason score ≥8, 74% had bone metastases, 63% lymph node metastases and 26% visceral metastases. All patients received docetaxel prior to cabazitaxel, 6 patients (31,6%) received abiraterone and 15 patients (78,9%) enzalutamide. Combination therapy was initiated after a median of 4.1 cycles monotherapy [IQR 3.0-6.0]. Patients were treated with a median of 3.8 [IQR 2.8-6.3] cycles of combination therapy. Eight patients (42,2%) had a PSA decrease of > 25% and 4 patients (21,1%) had a PSA decrease of ≥50%. One patient had a WHO PS improvement of 2. Median PFS was 8.1 [IQR 6.0-15.1] months and median OS 13.0 months. Anemia was the most common adverse event (≥ grade 2) during combination therapy (62%), while thrombopenia was only found in one patient (5%). Other common adverse events were fatigue (43%), nausea (24%), pain (33%) and constipation (10%). Conclusions: Our data suggests that combination treatment of cabazitaxel and carboplatin might be effective in heavily pretreated patients not, or no longer responding to cabazitaxel monotherapy.

Endogenous androgen receptor proteomic profiling reveals genomic subcomplex involved in prostate tumorigenesis

Androgen receptor (AR) is a key player in prostate cancer development and progression. Here we applied immunoprecipitation mass spectrometry of endogenous AR in LNCaP cells to identify components of the AR transcriptional complex. In total, 66 known and novel AR interactors were identified in the presence of synthetic androgen, most of which were critical for AR-driven prostate cancer cell proliferation. A subset of AR interactors required for LNCaP proliferation were profiled using chromatin immunoprecipitation assays followed by sequencing, identifying distinct genomic subcomplexes of AR interaction partners. Interestingly, three major subgroups of genomic subcomplexes were identified, where selective gain of function for AR genomic action in tumorigenesis was found, dictated by FOXA1 and HOXB13. In summary, by combining proteomic and genomic approaches we reveal subclasses of AR transcriptional complexes, differentiating normal AR behavior from the oncogenic state. In this process, the expression of AR interactors has key roles by reprogramming the AR cistrome and interactome in a genomic location-specific manner.

Randomized Phase III Study to Assess Efficacy and Safety of Adjuvant CAPOX with or without Bevacizumab in Patients after Resection of Colorectal Liver Metastases: HEPATICA study

Bevacizumab is a humanized monoclonal antibody targeting vascular endothelial growth factor (VEGF). Recurrence after resection of colorectal liver metastases (CRLMs), presumably caused by VEGF-mediated outgrowth of micrometastases, might decrease when VEGF is inhibited. This study examines the efficacy and safety of adding bevacizumab to an adjuvant regimen of CAPOX in patients undergoing radical resection for their CRLMs. Patients with resected CRLMs were randomized after surgery to receive CAPOX and bevacizumab (arm A) or CAPOX alone (arm B) as adjuvant treatment. CAPOX was given in both arms for a total of eight cycles. Bevacizumab was administered for 16 cycles. The primary end point was disease-free survival (DFS). Secondary outcomes were overall survival (OS), toxicity, and quality of life (QoL). In total, 79 patients were randomized. At the time of analysis, 23 events were encountered in arm A and 20 in arm B. One-year DFS rate was 79% [95% confidence interval (CI): 68%-93%] and 68% (95% CI: 55%-85%) for arm A and B, respectively (P = .89). Toxicity was evaluated for 75 patients. No significant differences in toxicity between the two arms were found. QoL scores were higher in arm A, of which emotional functioning and global QoL scores were significant. Adding bevacizumab to a CAPOX regimen in patients undergoing a resection for their CLM is safe and showed higher QoL scores compared with CAPOX alone. Because of premature closure of the study, conclusions about the effect on DFS of additional VEGF inhibition in this setting could not yet be made.

A phase I study of chemoradiation with weekly panitumumab following neoadjuvant chemotherapy and pelvic lymph node dissection as an organ preserving treatment of invasive bladder cancer

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Background: Radical Cystectomy (RC) is the standard treatment of Invasive Bladder Cancer (IBC). Although organ sparing, external beam Radiation Treatment (RT) alone is considered inferior to RC. Since the Epidermal Growth Factor receptor (EGFr) is frequently overexpressed in IBC, combined EGFr inhibition by Panitumumab (P) and RT might improve treatment outcome. In this study, the safety and efficacy of concurrent RT and P (RT/P) following Neoadjuvant Chemotherapy (NAC) and Pelvic Lymph Node Dissection (PLND) was evaluated. Methods: cT2-4N0-2M0 or cT1N1-2M0 bladder cancer patients were enrolled in the study. NAC consisted of a maximum of 4 cycles platinum-based chemotherapy. cN0 patients received NAC after PLND, while cN+ patients (confirmed by fine needle aspiration) received NAC prior to PLND. RT/P consisted of concurrent P (7 weekly doses of 2.5 mg/kg) and bladder RT (66Gy in 33 fractions). Primary end-points were treatment-related toxicity and complete clinical response (CR) assessed by Computed Tomography and cystoscopy 3 months after therapy completion. Partial response (PR) was defined as cT < 2N0. Results: A total of 31 patients were included (mean age: 60±10 years), 3/31 patients were cN1-2. Three patients discontinued NAC after 3 cycles due to toxicity. After NAC (24 cisplatin-based and 7 gemcitabine/carboplatin) 13 (41.9%) patients had remaining visible disease. All patients completed RT, while 4/31 patients terminated P prematurely (2-6 doses) due to toxicity. Preliminary response results after RT/P were available for 29/31 patients. Twenty-six/29 (89.7%) patients had a CR, 3 patients PR (10.3%) of which 2 were treated with transurethral resection and intravesical treatment (TaG1-2) and 1 patient underwent immediate cystectomy after histologic confirmation of T1G3. Conclusions: These preliminary results suggest that concurrent P and RT following NAC and PLND is an organ-preserving option for IBC. Toxicity, EGFr expression, mutational status and long-term oncologic outcomes have to be awaited. Clinical trial information: NL31148.031.10.

Final analysis of COMET-1: Cabozantinib (Cabo) versus prednisone (Pred) in metastatic castration-resistant prostate cancer (mCRPC) patients (pts) previously treated with docetaxel (D) and abiraterone (A) and/or enzalutamide (E)

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Background: Cabo inhibits tyrosine kinases including MET and VEGFRs. In a phase 2 study in mCRPC pts, Cabo was associated with improvements in bone scans, pain, measurable disease, and circulating tumor cells. COMET-1 compared the effects of Cabo versus Pred on overall survival (OS) in men with progressive mCRPC and prior D and A and/or E. Methods: In this randomized, double-blind, controlled phase 3 study (NCT01605227), pts with mCRPC and prior D and A and/or E were randomized 2:1 to receive Cabo (60 mg qd) or Pred (5 mg bid). Pts were stratified by prior treatment with cabazitaxel, ECOG status, and presence of moderate to severe pain. The primary endpoint was OS. The study was designed to observe 578 deaths to provide 90% power to detect a hazard ratio (HR) of 0.75. A secondary endpoint was bone scan response at Week 12 (BSR) determined by central independent radiology committee, defined as a ≥30% decrease in the bone scan lesion area compared to baseline. Exploratory endpoints include PFS and OS subgroup analyses. Results: 1,028 pts were randomized between Jul 2012 and Nov 2013. In the final analysis after 614 deaths, the estimated median OS was 11.0 months for Cabo vs 9.8 months for Pred (HR 0.90; 95% CI: 0.0.76-1.06; P = 0.212). The secondary endpoint of BSR was 41% for Cabo vs 3% for Pred (P <0.001). Median PFS per investigator was 5.5 months for Cabo vs 2.8 months for Pred (HR 0.50; P <0.001). For 191 pts with visceral disease median OS was 7.1 months for Cabo vs 4.8 months for Pred (HR 0.65; P = 0.0215). 371 (54.4%) and 233 (67.3%) pts received salvage therapy in the Cabo and Pred arms, respectively. Subsequent cabazitaxel and/or D was reported in 107 (15.7%) and 104 (30.1%) Cabo and Pred pts, respectively. Serious adverse events of pulmonary embolism, nausea, dehydration and fatigue were more frequent with Cabo. Conclusions: Compared to prednisone, Cabo improved BSR and PFS but did not significantly increase OS. The improvement in OS was greatest in the subset of patients with visceral metastases. The activity and safety profile of Cabo was similar to that observed in phase 2 studies in mCRPC. Clinical trial information: NCT01605227.

Fibroblast growth factor receptor 3 activation plays a causative role in urothelial cancer pathogenesis in cooperation with Pten loss in mice

Although somatic mutations and overexpression of the tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) are strongly associated with bladder cancer, evidence for their functional involvement in the pathogenesis remains elusive. Previously we showed that activation of Fgfr3 alone is not sufficient to initiate urothelial tumourigenesis in mice. Here we hypothesize that cooperating mutations are required for Fgfr3-dependent tumourigenesis in the urothelium and analyse a mouse model in which an inhibitor of Pi3k-Akt signalling, Pten, is deleted in concert with Fgfr3 activation (UroIICreFgfr3(+/) (K644E) Pten(flox) (/flox)). Two main phenotypical characteristics were observed in the urothelium: increased urothelial thickness and abnormal cellular histopathology, including vacuolization, condensed cellular appearance, enlargement of cells and nuclei, and loss of polarity. These changes were not observed when either mutation was present individually. Expression patterns of known urothelial proteins indicated the abnormal cellular differentiation. Furthermore, quantitative analysis showed that Fgfr3 and Pten mutations cooperatively caused cellular enlargement, while Pten contributed to increased cell proliferation. Finally, FGFR3 overexpression was analysed along the level of phosphorylated mTOR in 66 T1 urothelial tumours in tissue microarray, which supported the occurrence of functional association of these two signalling pathways in urothelial pathogenesis. Taken together, this study provides evidence supporting a functional role of FGFR3 in the process of pathogenesis in urothelial neoplasms. Given the wide availability of inhibitors specific to FGF signalling pathways, our model may open the avenue for FGFR3-targeted translation in urothelial disease.

Induction chemotherapy followed by surgery in node positive bladder cancer

OBJECTIVE

To evaluate the outcome and prognostic factors of patients with node positive bladder cancer (NPBC), who were eligible for surgery and treated with induction chemotherapy.

METHODS

All consecutive patients with NPBC, who were treated with at least 2 cycles of induction chemotherapy and initially scheduled for surgery, between 1990 and 2012, were identified from an institutional bladder cancer database. Induction chemotherapy consisted of MVAC (methotrexate, vinblastine, doxorubicin, and cisplatin) or gemcitabine with cisplatin (Gem/Cis) or carboplatin (Gem/Carbo).

RESULTS

One hundred forty-nine patients with NPBC (mean age, 60 years; range, 31-79) were treated with induction chemotherapy. Median cancer-specific survival (CSS) was 20 months and 5-year CSS 29.2%. In case of complete pathologic response to induction chemotherapy (N = 40; 26.8%), median CSS was 127 months and 5-year CSS 63.5% (P <.0001). Clinical and pathologic responses to chemotherapy were predictive parameters with respect to CSS and recurrence-free survival. Combined local and nodal responses resulted in a significantly better outcome, compared with isolated nodal or local response (P <.0001).

CONCLUSION

Prognosis for NPBC remains poor despite the use of induction chemotherapy. Nevertheless, in the present series, 1 of 4 patients showed complete pathologic response to induction chemotherapy with subsequently a significant CSS benefit (median CSS 127 months and 5-year CSS 63.5%). Clinical and pathologic responses to chemotherapy are predictive parameters for outcome.

Abstract 1268: The role of the adaptive immune system in initiation and progression in two independent spontaneous mouse models for prostate cancer

Increasing evidence from epidemiological and pathology studies indicates a role of the immune system in initiation and progression of multiple cancers, including prostate cancer. However, reports on the specific role of the immune system are contradictive since both suppression and acceleration of disease progression have been described. Overexpression of MYC and loss of PTEN are frequent genetic lesions in prostate cancer. It has been shown that these lesions induce chemokine expression, attraction of immune cells and subsequent angiogenesis and disease progression in cancer models.

In this study we address the role of the adaptive immune system in prostate cancer progression in two independent spontaneous prostate cancer mouse models; the FVB/HiMYC mouse model in which prostate cancer formation is driven by transgenic expression of human MYC under control of the ARR2/probasin promoter, and the PB-Cre;PTENF/F mouse model in which prostate cancer formation is initiated by loss of PTEN expression. Both mouse models develop Prostatic Intraepithelial Neoplasia (PIN) from the age of 4 weeks on. FVB/HiMYC mice develop invasive carcinoma from the age of 24 weeks and PB-Cre;PTENF/F mice from the age of 12 weeks on. To address the functional significance of lymphocytes in prostate cancer development, FVB/HiMYC and PB-Cre;PTENF/F were crossed to lymphocyte deficient RAG-1−/− mice. Preliminary data suggest that both mouse models crossed to RAG-1−/− have a longer latency of invasive carcinoma development and less extensive lesions than RAG-1+/− mice, suggesting an important role of the adaptive immune system in prostate cancer initiation and/or progression.

Marked inflammation and increased nuclear BrdU incorporation was found in concert with prostate cancer development using immunohistochemistry. Flow cytometry confirmed an increase in CD45 positive cells in the prostate, which was not observed in blood. Studies to identify the lymphocyte population with a key role in prostate cancer development and to dissect the exact mechanism of growth promotion are currently ongoing. In addition, we will verify whether the identified immune cells and soluble mediators in the in vivo models are also found in human prostate cancer samples.

In conclusion: Our study provides insight into the role of the adaptive immune system in prostate cancer development. These data might serve as a basis to develop intervention strategies that intersect with the supportive role of the immune system in human prostate carcinogenesis.

Citation Format: Monique H.M Melis, Johan van Burgsteden, Hester J.T. van Zeeburg, John Zevenhoven, Ji-Ying Song, Karin E. de Visser, Andre M. Bergman. The role of the adaptive immune system in initiation and progression in two independent spontaneous mouse models for prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1268. doi:10.1158/1538-7445.AM2013-1268

A randomized two arm phase III study in patients post radical resection of liver metastases of colorectal cancer to investigate bevacizumab in combination with capecitabine plus oxaliplatin (CAPOX) vs CAPOX alone as adjuvant treatment

Background

About 50% of patients with colorectal cancer are destined to develop hepatic metastases. Radical resection is the most effective treatment for patients with colorectal liver metastases offering five year survival rates between 36-60%. Unfortunately only 20% of patients are resectable at time of presentation. Radiofrequency ablation is an alternative treatment option for irresectable colorectal liver metastases with reported 5 year survival rates of 18-30%. Most patients will develop local or distant recurrences after surgery, possibly due to the outgrowth of micrometastases present at the time of liver surgery. This study aims to achieve an improved disease free survival for patients after resection or resection combined with RFA of colorectal liver metastases by adding the angiogenesis inhibitor bevacizumab to an adjuvant regimen of CAPOX.

Methods/design

The Hepatica study is a two-arm, multicenter, randomized, comparative efficacy and safety study. Patients are assessed no more than 8 weeks before surgery with CEA measurement and CT scanning of the chest and abdomen. Patients will be randomized after resection or resection combined with RFA to receive CAPOX and Bevacizumab or CAPOX alone. Adjuvant treatment will be initiated between 4 and 8 weeks after metastasectomy or resection in combination with RFA. In both arms patients will be assessed for recurrence/new occurrence of colorectal cancer by chest CT, abdominal CT and CEA measurement. Patients will be assessed after surgery but before randomization, thereafter every three months after surgery in the first two years and every 6 months until 5 years after surgery. In case of a confirmed recurrence/appearance of new colorectal cancer, patients can be treated with surgery or any subsequent line of chemotherapy and will be followed for survival until the end of study follow up period as well. The primary endpoint is disease free survival. Secondary endpoints are overall survival, safety and quality of life.

Conclusion

The HEPATICA study is designed to demonstrate a disease free survival benefit by adding bevacizumab to an adjuvant regime of CAPOX in patients with colorectal liver metastases undergoing a radical resection or resection in combination with RFA.

Trial Registration

ClinicalTrials.gov Identifier NCT00394992

Development and operation of research-scale III-V nanowire growth reactors

III-V nanowires are useful platforms for studying the electronic and mechanical properties of materials at the nanometer scale. However, the costs associated with commercial nanowire growth reactors are prohibitive for most research groups. We developed hot-wall and cold-wall metal organic vapor phase epitaxy reactors for the growth of InAs nanowires, which both use the same gas handling system. The hot-wall reactor is based on an inexpensive quartz tube furnace and yields InAs nanowires for a narrow range of operating conditions. Improvement of crystal quality and an increase in growth run to growth run reproducibility are obtained using a homebuilt UHV cold-wall reactor with a base pressure of 2x10(-9) Torr. A load lock on the UHV reactor prevents the growth chamber from being exposed to atmospheric conditions during sample transfers. Nanowires grown in the cold-wall system have a low defect density, as determined using transmission electron microscopy, and exhibit field effect gating with mobilities approaching 16,000 cm(2)/(V s).

Monte Carlo calculation of dose distribution in early stage NSCLC patients planned for accelerated hypofractionated radiation therapy in the NCIC-BR25 protocol

The dosimetric consequences of plans optimized using a commercial treatment planning system (TPS) for hypofractionated radiation therapy are evaluated by re-calculating with Monte Carlo (MC). Planning guidelines were in strict accordance with the Canadian BR25 protocol which is similar to the RTOG 0236 and 0618 protocols in patient eligibility and total dose, but has a different hypofractionation schedule (60 Gy in 15 fractions versus 60 Gy in 3 fractions). A common requirement of the BR25 and RTOG protocols is that the dose must be calculated by the TPS without tissue heterogeneity (TH) corrections. Our results show that optimizing plans using the pencil beam algorithm with no TH corrections does not ensure that the BR25 planning constraint of 99% of the PTV receiving at least 95% of the prescription dose would be achieved as revealed by MC simulations. This is due to poor modelling of backscatter and lateral electronic equilibrium by the TPS. MC simulations showed that as little as 75% of the PTV was actually covered by the 95% isodose line. The under-dosage of the PTV was even more pronounced if plans were optimized with the TH correction applied. In the most extreme case, only 23% of the PTV was covered by the 95% isodose.

Gemcitabine uptake in glioblastoma multiforme: potential as a radiosensitizer

Glioblastoma multiforme (GBM), the most frequent malignant brain tumor, has a poor prognosis, but is relatively sensitive to radiation. Both gemcitabine and its metabolite difluorodeoxyuridine (dFdU) are potent radiosensitizers. The aim of this phase 0 study was to investigate whether gemcitabine passes the blood-tumor barrier, and is phosphorylated in the tumor by deoxycytidine kinase (dCK) to gemcitabine nucleotides in order to enable radiosensitization, and whether it is deaminated by deoxycytidine deaminase (dCDA) to dFdU. Gemcitabine was administered at 500 or 1000 mg/m(2) just before surgery to 10 GBM patients, who were biopsied after 1-4 h. Plasma gemcitabine and dFdU levels varied between 0.9 and 9.2 microM and 24.9 and 72.6 microM, respectively. Tumor gemcitabine and dFdU levels varied from 60 to 3580 pmol/g tissue and from 29 to 72 nmol/g tissue, respectively. The gene expression of dCK (beta-actin ratio) varied between 0.44 and 2.56. The dCK and dCDA activities varied from 1.06 to 2.32 nmol/h/mg protein and from 1.51 to 5.50 nmol/h/mg protein, respectively. These enzyme levels were sufficient to enable gemcitabine phosphorylation, leading to 130-3083 pmol gemcitabine nucleotides/g tissue. These data demonstrate for the first time that gemcitabine passes the blood-tumor barrier in GBM patients. In tumor samples, both gemcitabine and dFdU concentrations are high enough to enable radiosensitization, which warrants clinical studies using gemcitabine in combination with radiation.

Micro-array analysis of resistance for gemcitabine results in increased expression of ribonucleotide reductase subunits

To study in detail the relation between gene expression and resistance against gemcitabine, a cell line was isolated from a tumor for which gemcitabine resistance was induced in vivo. Similar to the in vivo tumor, resistance in this cell line, C 26-G, was not related to deficiency of deoxycytidine kinase (dCK). Micro-array analysis showed increased expression of ribonucleotide reductase (RR) subunits M1 and M2 as confirmed by real time PCR analysis (28- and 2.7-fold, respectively). In cell culture, moderate cross-resistance (about 2-fold) was observed to 1-ss-D-arabinofuranosylcytosine (ara-C), 2-chloro-2'deoxyadenosine (CdA), LY231514 (ALIMTA), and cisplatin (CDDP), and pronounced cross-resistance (>23-fold) to 2',2'-difluorodeoxyuridine (dFdU) and 2',2'-difluorodeoxyguanosine (dFdG). Culture in the absence of gemcitabine reduced resistance as well as RRM1 RNA expression, demonstrating a direct relationship of RRM1 RNA expression with acquired resistance to gemcitabine.

The synergistic interaction of gemcitabine and cytosine arabinoside with the ribonucleotide reductase inhibitor triapine is schedule dependent

Gemcitabine and ara-C have multiple mechanisms of action: DNA incorporation and for gemcitabine also ribonucleotide reductase (RNR) inhibition. Since dCTP competes with their incorporation into DNA, dCTP depletion can potentiate their cytotoxicity. We investigated whether additional RNR inhibition by Triapine (3-AP), a new potent RNR inhibitor, enhanced cytotoxicity of gemcitabine and ara-C in four non-small-cell-lung-cancer (NSCLC) cell lines, using the multiple-drug-effect analysis. Simultaneous and sequential exposure (preexposure to 3-AP for 24h) in a constant molar ratio of 3-AP and gemcitabine was antagonistic/additive in all cell lines. Preexposure to 3-AP at an IC(25) concentration for 24h before variable concentrations of gemcitabine was synergistic. RNR inhibition by 3-AP resulted in a more synergistic interaction in combination with ara-C, which does not inhibit RNR. Two cell lines with pronounced synergism (SW1573) or antagonism (H460) for gemcitabine/3-AP, were evaluated for accumulation of the active metabolites, dFdCTP and ara-CTP. Simultaneous exposure induced no or a small increase, but ara-CTP increased after pretreatment with 3-AP, 4-fold in SW1573 cells, but not in H460 (<1.5 fold). Ara-C and gemcitabine incorporation into DNA were more pronounced (about 2-fold increased) for sequential treatment in SW1573 compared to H460 cells (<1.5 fold). This was not related to the activity and expression of deoxycytidine kinase and the M2 subunit of RNR. In conclusion, RNR inhibition by 3-AP prior to gemcitabine or ara-C exposure stimulates accumulation of the active metabolites and incorporation into DNA. The combination 3-AP/Ara-C is more synergistic than 3-AP/gemcitabine possibly because gemcitabine already inhibits RNR, but ara-C does not.

Antiproliferative activity and mechanism of action of fatty acid derivatives of arabinosylcytosine (ara-C) in leukemia and solid tumor cell lines

Resistance to, the hydrophilic drug ara-C, might be meditated by decreased membrane transport. Lipophilic prodrugs were synthesized to facilitate uptake. These compounds were equally active as ara-C, while the compounds with the shortest fatty-acid group and highest number of double bonds were the more active. These compounds also show a better retention profile, their effect is retained longer than for ara-C.

Antiproliferative activity and mechanism of action of fatty acid derivatives of gemcitabine in leukemia and solid tumor cell lines and in human xenografts

Gemcitabine is a deoxycytidine analog, which can be inactivated by deamination catalyzed by deoxycytidine deaminase (dCDA). Altered transport over the cell membrane is a mechanism of resistance to gemcitabine. To facilitate accumulation, the fatty acid derivative CP-4125 was synthesized. Since, the fatty acid is acylated at the site of action of dCDA, a decreased deamination was expected. CP-4125 was equally active as gemcitabine in a panel of rodent and human cell lines and in human melanoma xenografts bearing mice. In contrast to gemcitabine, CP-4125 was not deaminated but inhibited deamination of deoxycytidine and gemcitabine. Pools of the active triphosphate of gemcitabine increased for over 20 hr after CP-4125 exposure, while these pools decreased directly after removal of gemcitabine.

IN CONCLUSION

CP-4125 is an interesting new gemcitabine derivative.

Antiproliferative activity and mechanism of action of fatty acid derivatives of arabinofuranosylcytosine in leukemia and solid tumor cell lines

1-beta-D-arabinofuranosylcytosine (ara-C) is a deoxycytidine analog with activity in leukemia, which requires phosphorylation by deoxycytidine kinase (dCK) to allow formation of its active phosphate 1-beta-D-arabinofuranosylcytosine triphosphate, but can be deaminated by deoxycytidine deaminase. Altered membrane transport is also a mechanism of drug resistance. In order to facilitate ara-C uptake and prolong retention in the cell, lipophilic prodrugs were synthesized. Fatty acid groups with a varying acyl chain length and number of double bonds were esterified at the 5' position on the sugar moiety of ara-C. The compounds were tested in two pairs of ara-C resistant leukemic cell lines (murine L1210 and rat BCLO and their resistant variants L4A6 and Bara-C, respectively) and two pairs of cell lines with a resistance to gemcitabine, another deoxycytidine analog (human ovarian cancer A2780 and murine colon cancer C26-A and their resistant variants AG6000 and C26-G, respectively). L4A6, Bara-C and AG6000 have varying degrees of decreased dCK activity, while the mechanism for C26-G is not yet clear. In the parent cell lines, ara-C was more active, but in the resistant variants several of the analogs were more active, while the degree of cross-resistance varied. In AG6000 with a total dCK deficiency, all compounds were inactive. Structure-activity relation analysis showed that ara-C derivatives with shorter acyl chains and more double bonds were more active in the parental and drug resistant cells. Further mechanistic studies were performed with the elaidic acid derivative of ara-C (CP-4055). CP-4055 inhibited deamination of dCyd partly and induced DNA synthesis inhibition effectively in C26-A and C26-G cells, but the retention of inhibition was much longer for CP-4055 than for ara-C. In contrast to ara-C, CP-4055 inhibited RNA synthesis for 60% after drug exposure. In conclusion, CP-4055 seems to be a promising prodrug, whose effects were different and longer lasting than for the parent drug.

Increased sensitivity to gemcitabine of P-glycoprotein and multidrug resistance-associated protein-overexpressing human cancer cell lines

Gemcitabine (2',2'-difluorodeoxycytidine) is a deoxycytidine analogue that is activated by deoxycytidine kinase (dCK) to its monophosphate and subsequently to its triphosphate dFdCTP, which is incorporated into both RNA and DNA, leading to DNA damage. Multidrug resistance (MDR) is characterised by an overexpression of the membrane efflux pumps P-glycoprotein (P-gP) or multidrug resistance-associated protein (MRP). Gemcitabine was tested against human melanoma, non-small-cell lung cancer, small-cell lung cancer, epidermoid carcinoma and ovarian cancer cells with an MDR phenotype as a result of selection by drug exposure or by transfection with the mdr1 gene. These cell lines were nine- to 72-fold more sensitive to gemcitabine than their parental cell lines. The doxorubicin-resistant cells 2R120 (MRP1) and 2R160 (P-gP) were nine- and 28-fold more sensitive to gemcitabine than their parental SW1573 cells, respectively (P<0.01), which was completely reverted by 25 micro M verapamil. In 2R120 and 2R160 cells, dCK activities were seven- and four-fold higher than in SW1573, respectively, which was associated with an increased dCK mRNA and dCK protein. Inactivation by deoxycytidine deaminase was 2.9- and 2.2-fold decreased in 2R120 and 2R160, respectively. dFdCTP accumulation was similar in SW1573 and its MDR variants after 24 h exposure to 0.1 micro M gemcitabine, but dFdCTP was retained longer in 2R120 (P<0.001) and 2R160 (P<0.003) cells. 2R120 and 2R160 cells also incorporated four- and six-fold more [(3)H]gemcitabine into DNA (P<0.05), respectively. P-glycoprotein and MRP1 overexpression possibly caused a cellular stress resulting in increased gemcitabine metabolism and sensitivity, while reversal of collateral gemcitabine sensitivity by verapamil also suggests a direct relation between the presence of membrane efflux pumps and gemcitabine sensitivity.

Effect of gemcitabine and cis-platinum combinations on ribonucleotide and deoxyribonucleotide pools in ovarian cancer cell lines

Gemcitabine (dFdC) and cisplatin (CDDP) act synergistically by an increase in platinum-DNA adduct formation. Since ribonucleotide (NTP) and deoxyribonucleotide (dNTP) levels are essential for DNA-synthesis and repair of DNA damage, we investigated whether disturbances might account for differences in effects between sensitive and resistant cell lines. The human ovarian cancer cell line A2780, its CDDP-resistant variant ADDP and its dFdC-resistant variant AG6000 were exposed for 24 h to dFdC or CDDP alone, or a combination causing moderate to strong growth inhibition. In AG6000 cells UTP levels were 2-fold lower and in ADDP cells almost 2-fold higher than in A2780 cells. Levels of dTTP, dATP and dCTP were 2-5-fold lower in the resistant cell lines. Drug treatment affected NTP and dNTP levels most pronounced in A2780 cells. dFdC alone, at 1.5 nM to 1 micro M increased ATP, GTP and CTP pools 1.2 to 2.0-fold, while 10 micro M dFdC increased UTP 2.5-fold. Combination of dFdC and CDDP increased all NTP levels at low dFdC and CDDP concentrations more than 1.2-fold, but at 20 micro M CDDP only CTP increased 2.4-fold. Only 1.5 nM dFdC increased all dNTP pools more than 1.6-fold, but at 0.1 and 1 micro M dFdC, dATP and dGTP decreased down to 10-fold, while dTTP increased 3-5-fold. CDDP and the combination increased all dNTP pools over 1.4 and 1.9-fold, respectively. In AG6000 cells dFdC and CDDP hardly affected the NTP and dNTP status, except at the high concentrations, which decreased ATP, GTP and UTP levels 1.2-1.8-fold. Both CDDP alone and the combination increased dTTP, dCTP and dATP pools up to 1.6-fold. In ADDP cells NTP and most dNTP levels were hardly affected, except dGTP levels which decreased to non-detectable levels. In conclusion, both dFdC and CDDP induce concentration and combination dependent changes in NTP and dNTP pools.

Collateral sensitivity to gemcitabine (2',2'-difluorodeoxycytidine) and cytosine arabinoside of daunorubicin- and VM-26-resistant variants of human small cell lung cancer cell lines

Multidrug resistance (MDR), characterized by a cross-resistance to many natural toxin-related compounds, may be caused either by overexpression of a drug efflux pump such as P-glycoprotein, (P-gP), multidrug resistance proteins MRP1-3, or BCRP/MXR or, in the case of DNA topoisomerase II active drugs, by a decrease in the enzymatic activity of the target molecule termed altered topoisomerase MDR (at-MDR). However, human small cell lung carcinoma (SCLC) cell lines showed a collateral sensitivity to 2',2'-difluorodeoxycytidine (gemcitabine, dFdC) and 1-beta-D-arabinofuranosylcytosine (ara-C). H69/DAU, a daunorubicin (DAU)-resistant variant of H69 with a P-gP overexpression, and NYH/VM, a VM-26 (teniposide)-resistant variant of NYH with an at-MDR, were both 2-fold more sensitive to gemcitabine and 7- and 2-fold more sensitive to ara-C, respectively. MDR variants had a 4.3- and 2.0-fold increased activity of deoxycytidine kinase (dCK), respectively. dCK catalyzes the first rate-limiting activation step of both gemcitabine and ara-C. In addition, deoxycytidine deaminase, responsible for inactivation of dFdC and ara-C, was 9.0-fold lower in H69/DAU cells. The level of thymidine kinase 2, a mitochondrial enzyme that can also phosphorylate deoxycytidine and gemcitabine, was not significantly different between the variants. These differences most likely caused an increased accumulation of the active metabolites (dFdCTP, 2.1- and 1.6-fold in NYH/VM and H69/DAU cells, respectively) and of ara-CTP (1.3-fold in NYH/VM cells). Ara-CTP accumulation was not detectable in either H69 variant. The pools of all ribonucleoside and deoxyribonucleoside triphosphates were at least 3- to 4-fold higher in the NYH variants compared to the H69 variants; for dCTP and dGTP this difference was even larger. The higher ribonucleotide pools might explain the >10-fold higher accumulation of dFdCTP in NYH compared to H69 variants. Since dCTP is low, H69 cells might not need a high ara-CTP accumulation to inhibit DNA polymerase. This might be related to the lack of ara-CTP in H69 variants. In addition, the increased CTP, ATP, and UTP pools in the MDR variants might explain the increased ara-CTP and dFdCTP accumulation. In conclusion, the MDR variants of the human SCLC cell lines were collaterally sensitive due to an increased dCK activity, and consequently an increased ara-CTP and dFdCTP accumulation.

Steroids affect collateral sensitivity to gemcitabine of multidrug-resistant human lung cancer cells

Gemcitabine is phosphorylated by deoxycytidine kinase and thymidine kinase 2 and during S-phase incorporated into DNA. The steroids cortisol and dexamethasone, which regulate cell proliferation and gene expression, are pumped out of the cell by the membrane efflux pumps P-glycoprotein and multidrug resistance-associated protein (MRP), which are blocked by verapamil. In parental non-small cell lung cancer (NSCLC) cells (SW1573), 5 microM cortisol and 100 nM dexamethasone decreased sensitivity to gemcitabine. However, both cortisol and dexamethasone only decreased sensitivity with verapamil in MRP (2R120) and P-glycoprotein (2R160) overexpressing variants. Cortisol decreased deoxycytidine kinase activity in SW1573 cells and cortisol with verapamil in 2R120 and 2R160 cells. Dexamethasone with verapamil decreased deoxycytidine kinase activity in 2R160. Cortisol decreased thymidine kinase 2 activity in 2R120 and 2R160 cells. Dexamethasone decreased thymidine kinase 2 activity in SW1573, 2R120 and 2R160 cells. In conclusion, since dexamethasone is frequently used to treat side effects of oncolytic therapy, a decrease of sensitivity to gemcitabine by steroids might be clinically relevant.

Cross-resistance in the 2',2'-difluorodeoxycytidine (gemcitabine)-resistant human ovarian cancer cell line AG6000 to standard and investigational drugs

Gemcitabine (2'-2'-difluorodeoxycytidine; dFdC) is a deoxycytidine analogue which is effective against solid tumours, including lung cancer and ovarian cancer. dFdC requires phosphorylation by deoxycytidine kinase (dCK) for activation. In the human ovarian cancer cell line A2780 and its 30,000-fold dFdC-resistant variant AG6000 (P<0.001), we investigated the cross-resistance profile to several drugs. AG6000, which has a complete dCK deficiency, was approximately 1000-10,000-fold resistant to other deoxynucleoside analogues such as 1-beta-D-arabinofuranosyl cytosine, 2-chloro-deoxyadenosine, aza-deoxycytidine and 2', 2'-difluorodeoxyguanosine (dFdG) (P<0.001). dFdG can be activated by dCK and deoxyguanosine kinase (dGK), but the latter enzyme was not altered in AG6000 cells. Thus dFdG resistance was only due to dCK deficiency. AG6000 was 1.6- and 46.7-fold resistant to 5-fluorouracil (5-FU) and ZD1694, respectively (the latter was significant; P<0.01), which may be due to the 1.7-fold higher thymidylate synthase (TS) activity, but AG6000 cells were also 2. 7-fold resistant to the lipophilic TS inhibitor AG337 (P<0.05). Remarkably, AG6000 cells were 2.5-fold more sensitive to methotrexate (MTX) (P<0.01) than A2780 cells, but 1.6-fold more resistant to trimetrexate (TMQ) (P<0.10). However, no differences in reduced folate carrier activity, folylpolyglutamate synthetase (FPGS) activity and polyglutamation of MTX were found between the cell lines. AG6000 cells were approximately 2 to 7.5-fold more resistant to doxorubicin (DOX), daunorubicin (DAU), epirubicin and vincristine (VCR) (the latter was significant; P<0.02) and approximately 4-fold more resistant to the microtubule inhibitors paclitaxel and docetaxel (P<0.001). Fluorescent activated cell sorter (FACS) analysis revealed no P-glycoprotein (Pgp) or multidrug resistance-associated protein (MRP) expression, but less fluorescence of intercalated DAU in AG6000 cells. An approximately 2-fold resistance to the topoisomerase I and II inhibitors etoposide, CPT-11 and SN38 was found in AG6000 cells. Topoisomerase I and IIalpha RNA expression was decreased in AG6000 cells. AG6000 was 2.4, 2.4, 2.3 and 3.7-fold more resistant to EO9 (P<0.02), mitomycin-C (MMC) (P<0.05), cisplatin (CDDP) (P<0.10) and maphosphamide (MAPH), respectively. DT-diaphorase (DTD), which activates EO9, was 2.2-fold lower in AG6000 cells. CDDP resistance might be related to a reduced retention of DNA adducts in AG6000. However, glutathione levels were equal in A2780 and AG6000 cells. A 24 h exposure to DOX, VCR and paclitaxel at equimolar and equitoxic concentrations, resulted in more double-strand breaks (1.5- to 2-fold) in A2780 than in AG6000 cells. MAPH at 1120 nM and 17 nM of EO9 did not cause DNA damage in either cell line. In conclusion, AG6000 is a cell line highly cross-resistant to a wide variety of drugs. This cross-resistance might be related to altered enzyme activities and/or increased DNA repair.

Basis for effective combination cancer chemotherapy with antimetabolites

Most current chemotherapy regimens for cancer consist of empirically designed combinations, based on efficacy and lack of overlapping toxicity. In the development of combinations, several aspects are often overlooked: (1) possible metabolic and biological interactions between drugs, (2) scheduling, and (3) different pharmacokinetic profiles. Antimetabolites are used widely in chemotherapy combinations for treatment of various leukemias and solid tumors. Ideally, the combination of two or more agents should be more effective than each agent separately (synergism), although additive and even antagonistic combinations may result in a higher therapeutic efficacy in the clinic. The median-drug effect analysis method is one of the most widely used methods for in vitro evaluation of combinations. Several examples of classical effective antimetabolite-(anti)metabolite combinations are discussed, such as that of methotrexate with 6-mercaptopurine or leucovorin in (childhood) leukemia and 5-fluorouracil (5FU) with leucovorin in colon cancer. More recent combinations include treatment of acute-myeloid leukemia with fludarabine and arabinosylcytosine. Other combinations, currently frequently used in the treatment of solid malignancies, include an antimetabolite with a DNA-damaging agent, such as gemcitabine with cisplatin and 5FU with the cisplatin analog oxaliplatin. The combination of 5FU and the topoisomerase inhibitor irinotecan is based on decreased repair of irinotecan-induced DNA damage. These combinations may increase induction of apoptosis. The latter combinations have dramatically changed the treatment of incurable cancers, such as lung and colon cancer, and have demonstrated that rationally designed drug combinations offer new possibilities to treat solid malignancies.

Positron emission mammographic instrument: initial results

Performance characteristics of a positron emission mammographic (PEM) instrument were studied. This dedicated metabolic breast imaging system has spatial resolution of 2.8-mm full width at half maximum (FWHM), coincidence resolving time of 12-nsec FWHM, and absolute efficiency of 3%. Hot spots with diameter of 16 mm in a phantom with signal-to-background activity ratio of 6:1 were distinguishable with a scanning time of 5 minutes.

Differential effects of gemcitabine on ribonucleotide pools of twenty-one solid tumour and leukaemia cell lines

To gain a more detailed insight into the metabolism of 2', 2'-difluoro-2'-deoxycytidine (dFdC, gemcitabine, Gemzar) and its effect on normal ribonucleotide (NTP) metabolism in relation to sensitivity, we studied the accumulation of dFdCTP and the changes in NTP pools after dFdC exposure in a panel of 21 solid tumour and leukaemia cell lines. Both sensitivity to dFdC and accumulation of dFdCTP were clearly cell line-dependent: in this panel of cell lines, the head and neck cancer (HNSCC) cell line 22B appeared to be the most sensitive, whereas the small cell lung cancer (SCLC) cell lines were the least sensitive to dFdC. The human leukaemia cell line CCRF-CEM accumulated the highest concentration of dFdCTP, whereas the non-SCLC cell lines accumulated the least. Not only the amount of dFdCTP accumulation was clearly related to the sensitivity for dFdC (R=-0.61), but also the intrinsic CTP/UTP ratio (R=0.97). NTP pools were affected considerably by dFdC treatment: in seven cell lines dFdC resulted in a 1.7-fold depletion of CTP pools, in two cell lines CTP pools were unaffected, but in 12 cell lines CTP pools increased about 2-fold. Furthermore, a 1.6-1.9-fold rise in ATP, UTP and GTP pools was shown in 20, 19 and 20 out of 21 cell lines, respectively. Only the UTP levels after treatment with dFdC were clearly related to the amount of dFdCTP accumulating in the cell (R=0.64 (P<0.01)), but not to the sensitivity to dFdC treatment. In conclusion, we demonstrate that besides the accumulation of dFdCTP, the CTP/UTP ratio was clearly related to the sensitivity to dFdC. Furthermore, the UTP levels and the CTP/UTP ratio after treatment were related to dFdCTP accumulation. Therefore, both the CTP and UTP pools appear to play an important role in the sensitivity to dFdC.

Mechanisms of synergism between cisplatin and gemcitabine in ovarian and non-small-cell lung cancer cell lines

2',2'-Difluorodeoxycytidine (gemcitabine, dFdC) and cis-diammine-dichloroplatinum (cisplatin, CDDP) are active agents against ovarian cancer and non-small-cell lung cancer (NSCLC). CDDP acts by formation of platinum (Pt)-DNA adducts; dFdC by dFdCTP incorporation into DNA, subsequently leading to inhibition of exonuclease and DNA repair. Previously, synergism between both compounds was found in several human and murine cancer cell lines when cells were treated with these drugs in a constant ratio. In the present study we used different combinations of both drugs (one drug at its IC25 and the other in a concentration range) in the human ovarian cancer cell line A2780, its CDDP-resistant variant ADDP, its dFdC-resistant variant AG6000 and two NSCLC cell lines, H322 (human) and Lewis lung (LL) (murine). Cells were exposed for 4, 24 and 72 h with a total culture time of 96 h, and possible synergism was evaluated by median drug effect analysis by calculating a combination index (CI; CI < 1 indicates synergism). With CDDP at its IC25, the average CIs calculated at the IC50, IC75 IC90 and IC95 after 4, 24 and 72 h of exposure were < 1 for all cell lines, indicating synergism, except for the CI after 4 h exposure in the LL cell line which showed an additive effect. With dFdC at its IC25, the CIs for the combination with CDDP after 24 h were < 1 in all cell lines, except for the CIs after 4 h exposure in the LL and H322 cell lines which showed an additive effect. At 72 h exposure all CIs were < 1. CDDP did not significantly affect dFdCTP accumulation in all cell lines. CDDP increased dFdC incorporation into both DNA and RNA of the A2780 cell lines 33- and 79-fold (P < 0.01) respectively, and tended to increase the dFdC incorporation into RNA in all cell lines. In the AG6000 and LL cell lines, CDDP and dFdC induced > 25% more DNA strand breaks (DSB) than each drug alone; however, in the other cell lines no effect, or even a decrease in DSB, was observed. dFdC increased the cellular Pt accumulation after 24 h incubation only in the ADDP cell line. However, dFdC did enhance the Pt-DNA adduct formation in the A2780, AG6000, ADDP and LL cell lines (1.6-, 1.4-, 2.9- and 1.6-fold respectively). This increase in Pt-DNA adduct formation seems to be related to the incorporation of dFdC into DNA (r = 0.91). No increase in DNA platination was found in the H322 cell line. dFdC only increased Pt-DNA adduct retention in the A2780 and LL cell lines, but decreased the Pt-DNA adduct retention in the AG6000 cell line. In conclusion, the synergism between dFdC and CDDP appears to be mainly due to an increase in Pt-DNA adduct formation possibly related to changes in DNA due to dFdC incorporation into DNA.

Selective cell kill of the combination of gemcitabine and cisplatin in multilayered postconfluent tumor cell cultures

Both gemcitabine (2',2'-difluorodeoxycytidine, dFdC) and cisplatin (cis-diammine-dichloroplatinum) have significant anticancer activity against ovarian, head and neck, and non-small cell lung cancer (NSCLC). dFdC can be incorporated into DNA and RNA, and inhibit DNA repair, while cisplatin can form Pt-DNA adducts. We previously observed schedule-dependent synergism of the combination of dFdC and cisplatin in monolayer cell cultures. We now evaluated whether the combination would also enable selective cell kill in multilayered postconfluent cell cultures, since each compound showed variable activity in multilayered cells. The combination was tested in multilayered cultures from cell lines with a different histological origin: the human head and neck squamous cell carcinoma cell line UMSCC-22B (22B), the human NSCLC cell line H322, and ADDP, a cisplatin-resistant variant of the human ovarian cancer cell line A2780. Sensitivity of the multilayered cells was dependent on exposure duration and sequence of the drug combinations, which were added in a constant molar ratio (dFdC:cisplatin 1:100), with a total exposure time of 96 h. The type of interaction was related to the degree of resistance of the cell lines to either dFdC or cisplatin. Thus, the very sensitive 22B cells only showed an additive effect when cells were preincubated for 24 h with dFdC prior to exposure to the combination. In contrast, in the resistant ADDP and H322 cells, synergism was the most common profile (three out of four schedules tested). This is of special relevance when we take into account that these drugs only show cytostatic effects when administered alone, whereas the combination produced cytotoxic cell killing. In conclusion, combining dFdC with cisplatin can be at least additive, but synergistic in multilayered postconfluent cells resistant to dFdC and cisplatin.