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.

Gene-expression-based T-Cell-to-Stroma Enrichment (TSE) score predicts response to immune checkpoint inhibitors in urothelial cancer

Immune checkpoint inhibitors (ICI) improve overall survival in patients with metastatic urothelial cancer (mUC), but therapeutic success at the individual patient level varies significantly. Here we identify predictive markers of response, based on whole-genome DNA (n = 70) and RNA-sequencing (n = 41) of fresh metastatic biopsy samples, collected prior to treatment with pembrolizumab. We find that PD-L1 combined positivity score does not, whereas tumor mutational burden and APOBEC mutagenesis modestly predict response. In contrast, T cell-to-stroma enrichment (TSE) score, computed from gene expression signature data to capture the relative abundance of T cells and stromal cells, predicts response to immunotherapy with high accuracy. Patients with a positive and negative TSE score show progression free survival rates at 6 months of 67 and 0%, respectively. The abundance of T cells and stromal cells, as reflected by the TSE score is confirmed by immunofluorescence in tumor tissue, and its good performance in two independent ICI-treated cohorts of patients with mUC (IMvigor210) and muscle-invasive UC (ABACUS) validate the predictive power of the TSE score. In conclusion, the TSE score represents a clinically applicable metric that potentially supports the prospective selection of patients with mUC for ICI treatment.

Pharmacokinetic boosting of olaparib: A randomised, cross-over study (PROACTIVE-study)

BACKGROUND

Pharmacokinetic (PK) boosting is the intentional use of a drug-drug interaction to enhance systemic drug exposure. PK boosting of olaparib, a CYP3A-substrate, has the potential to reduce PK variability and financial burden. The aim of this study was to investigate equivalence of a boosted, reduced dose of olaparib compared to the non-boosted standard dose.

METHODS

This cross-over, multicentre trial compared olaparib 300 mg twice daily (BID) with olaparib 100 mg BID boosted with the strong CYP3A-inhibitor cobicistat 150 mg BID. Patients were randomised to the standard therapy followed by the boosted therapy, or vice versa. After seven days of each therapy, dense PK sampling was performed for noncompartmental PK analysis. Equivalence was defined as a 90% Confidence Interval (CI) of the geometric mean ratio (GMR) of the boosted versus standard therapy area under the plasma concentration-time curve (AUC0-12 h) within no-effect boundaries. These boundaries were set at 0.57-1.25, based on previous pharmacokinetic studies with olaparib capsules and tablets.

RESULTS

Of 15 included patients, 12 were eligible for PK analysis. The GMR of the AUC0-12 h was 1.45 (90% CI 1.27-1.65). No grade ≥3 adverse events were reported during the study.

CONCLUSIONS

Boosting a 100 mg BID olaparib dose with cobicistat increases olaparib exposure 1.45-fold, compared to the standard dose of 300 mg BID. Equivalence of the boosted olaparib was thus not established. Boosting remains a promising strategy to reduce the olaparib dose as cobicistat increases olaparib exposure Adequate tolerability of the boosted therapy with higher exposure should be established.

Improved enrichment of circulating tumor cells from diagnostic leukapheresis product

The median number of circulating tumor cells (CTCs) detected in 7.5 mL of peripheral blood by CellSearch (PB-CS) in patients with metastatic prostate cancer is in the order of 1-10, which means many samples have insufficient tumor cells for comprehensive characterization. A significant increase is obtained through diagnostic leukapheresis (DLA), however, only 2%-3% of the DLA product can be processed per CellSearch test, limiting the gain. We processed aliquots from 30 DLA products of metastatic prostate cancer patients consisting of 0.2 × 109 leukocytes using CellSearch (DLA-CS) as well as the newly introduced reduced enrichment reagent protocol (RER), which uses 10-fold less enrichment reagents than DLA-CS. The number of tumor cells and the total number of captured cells were determined using the CellTracks Analyzer. Additionally, for six DLA samples, a 1.0 × 109 leukocyte aliquot was processed (RER+), using twofold less enrichment reagents than DLA-CS. A median 2.7-fold reduction in leukocyte co-enrichment was found between DLA-CS and RER methods without any loss in tumor cell recovery (Wilcoxon Signed Ranks Test, p = 0.953). Using 1.0 × 109 leukocyte aliquots a fourfold increase in tumor cells was found compared to DLA-CS and a 19-fold increase compared to PB-CS was obtained. The here-introduced RER protocol results in a higher final sample purity without any loss in tumor cell recovery while using 10-fold less CellSearch capture reagent. With this improved method, 26% of the leukapheresis sample can now be processed using reagents from a single CellSearch test, enabling the obtainment of a sufficient number of CTCs for comprehensive characterization in most metastatic prostate cancer patients.

68Ga-PSMA PET/CT for Response Evaluation of 223Ra Treatment in Metastatic Prostate Cancer

CT and bone scintigraphy are not useful for response evaluation of bone metastases to 223Ra treatment in metastatic castration-resistant prostate cancer (mCRPC). PET using 68Ga prostate-specific membrane antigen 11 (68Ga-PSMA) is a promising tool for response evaluation of mCRPC. The aim of this study was to determine the utility of 68Ga-PSMA PET/CT for response evaluation of 223Ra treatment in patients with mCRPC. Methods: Within this prospective, multicenter, imaging discovery study, 28 patients with mCRPC, eligible for 223Ra treatment, were included between 2019 and 2022. Patients received 223Ra according to the standard of care. Study procedures included CT, bone scintigraphy, and 68Ga-PSMA PET/CT at baseline, after 3 and 6 cycles of 223Ra treatment, and on treatment failure. Response to 223Ra treatment was visually assessed on all 3 imaging modalities. Total tumor volume within bone (TTVbone) was determined on 68Ga-PSMA PET/CT. Intrapatient heterogeneity in response was studied using a newly developed image-registration tool for sequential images of PET/CT. Results were compared with failure-free survival (good responders vs. poor responders; cutoff, 24 wk) and alkaline phosphatase (ALP) response after 3 cycles. Results: Visual response assessment criteria could not distinguish good responders from poor responders on 68Ga-PSMA PET/CT and bone scintigraphy. For 68Ga-PSMA PET/CT, TTVbone at baseline was lower in good responders than in poor responders, whereas TTVbone increased in both groups during treatment. TTVbone was higher in patients with new extraosseous metastases during 223Ra treatment. Although TTVbone and ALP correlated at baseline, changes in TTVbone and ALP on treatment did not. 68Ga-PSMA response of TTVbone showed intrapatient heterogeneity in most patients. Conclusion: mCRPC patients with lower TTVbone on 68Ga-PSMA PET/CT have the best clinical outcome after 223Ra treatment. Response is highly heterogeneous in most patients. A decrease in ALP, which occurred in most patients, was not correlated with a decrease in TTVbone, which might make one question the value of ALP for disease monitoring during 223Ra treatment in clinical practice.

mFast-SeqS-based aneuploidy score in circulating cell-free DNA is a prognostic biomarker in prostate cancer

Multiple prognostic biomarkers, including circulating tumour cell (CTC) counts, exist in metastatic castration-resistant prostate cancer (mCRPC) patients, but none of them have been implemented into daily clinical care. The modified fast aneuploidy screening test-sequencing system (mFast-SeqS), which yields a genome-wide aneuploidy score, is able to reflect the fraction of cell-free tumour DNA (ctDNA) within cell-free DNA (cfDNA) and may be a promising biomarker in mCRPC. In this study, we investigated the prognostic value of dichotomized aneuploidy scores (< 5 vs. ≥ 5) as well as CTC counts (< 5 vs. ≥ 5) in 131 mCRPC patients prior to treatment with cabazitaxel. We validated our findings in an independent cohort of 50 similarly treated mCRPC patients. We observed that, similar to the dichotomized CTC count [HR: 2.92; 95% confidence interval (CI);1.84-4.62], dichotomized aneuploidy scores (HR: 3.24; CI: 2.12-4.94) significantly correlated with overall survival in mCRPC patients. We conclude that a dichotomized aneuploidy score from cfDNA is a prognostic marker for survival in mCRPC patients within our discovery cohort and in an independent mCRPC validation cohort. Therefore, this easy and robust minimally-invasive assay can be readily implemented as a prognostic marker in mCRPC. A dichotomized aneuploidy score might also be used as a stratification factor in clinical studies to account for tumour load.

Liquid Biopsies for Early Response Evaluation of Radium-223 in Metastatic Prostate Cancer

PURPOSE

Reliable biomarkers for response monitoring during radium-223 treatment in patients with metastatic castration-resistant prostate cancer (mCRPC) are lacking. Circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), obtained from liquid biopsies, are shown to have prognostic value in mCRPC. The aim of this study was to determine the value of CTCs and ctDNA for response evaluation of radium-223.

METHODS

In this prospective multicenter study, longitudinal blood draws and imaging were performed in 28 patients with mCRPC and predominantly bone disease, who were treated with radium-223. CTCs were counted (CELLSEARCH CTC test), while fraction of ctDNA was estimated by measuring aneuploidy of cell-free DNA (cfDNA; modified Fast Aneuploidy Screening Test-Sequencing System). CTC counts and aneuploidy score (AS) were categorized as low (<5) and high (≥5). Primary and secondary clinical end points were failure-free survival (FFS), and overall survival (OS) and development of extraosseous metastases, respectively. Additionally, CTC count and AS were related to alkaline phosphatase (ALP) and total tumor volume in bone (TTVbone) on positron emission tomography-computed tomography with 68gallium prostate-specific membrane antigen.

RESULTS

FFS was longer in patients with a low CTC count or AS either at baseline or after 12 weeks, whereas for OS, only a significant association with CTC count was observed. Liquid biopsy results correlated well with ALP and TTVbone at baseline, but not with change in both parameters after three cycles of radium-223. AS and CTC count were significantly correlated.

CONCLUSION

CTC count and AS of cfDNA at baseline and during treatment predict clinical response to radium-223 in patients with mCRPC, warranting future evaluation of their value in treatment guidance.

The PRO-RCC study: a long-term PROspective Renal Cell Carcinoma cohort in the Netherlands, providing an infrastructure for 'Trial within Cohorts' study designs

BACKGROUND

Ongoing research in the field of both localized, locally advanced and metastatic renal cell carcinoma has resulted in the availability of multiple treatment options. Hence, many questions are still unanswered and await further research. A nationwide collaborative registry allows to collect corresponding data. For this purpose, the Dutch PROspective Renal Cell Carcinoma cohort (PRO-RCC) has been founded, for the prospective collection of long-term clinical data, patient reported outcome measures (PROMs) and patient reported experience measures (PREMs).

METHODS

PRO-RCC is designed as a multicenter cohort for all Dutch patients with renal cell carcinoma (RCC). Recruitment will start in the Netherlands in 2023. Importantly, participants may also consent to participation in a 'Trial within cohorts' studies (TwiCs). The TwiCs design provides a method to perform (randomized) interventional studies within the registry. The clinical data collection is embedded in the Netherlands Cancer Registry (NCR). Next to the standardly available data on RCC, additional clinical data will be collected. PROMS entail Health-Related Quality of Life (HRQoL), symptom monitoring with optional ecological momentary assessment (EMA) of pain and fatigue, and optional return to work- and/or nutrition questionnaires. PREMS entail satisfaction with care. Both PROMS and PREMS are collected through the PROFILES registry and are accessible for the patient and the treating physician.

TRIAL REGISTRATION

Ethical board approval has been obtained (2021_218) and the study has been registered at ClinicalTrials.gov (NCT05326620).

DISCUSSION

PRO-RCC is a nationwide long-term cohort for the collection of real-world clinical data, PROMS and PREMS. By facilitating an infrastructure for the collection of prospective data on RCC, PRO-RCC will contribute to observational research in a real-world study population and prove effectiveness in daily clinical practice. The infrastructure of this cohort also enables that interventional studies can be conducted with the TwiCs design, without the disadvantages of classic RCTs such as slow patient accrual and risk of dropping out after randomization.

The genomic and transcriptomic landscape of advanced renal cell cancer for individualized treatment strategies

Differences in the clinical course and treatment responses in individual patients with advanced renal cell carcinoma (RCC) can largely be explained by the different genomics of this disease. To improve the personalized treatment strategy and survival outcomes for patients with advanced RCC, the genomic make-up in patients with advanced RCC was investigated to identify putative actionable variants and signatures. In this prospective multicenter study (NCT01855477), whole-genome sequencing (WGS) data of locally advanced and metastatic tissue biopsies and matched whole-blood samples were collected from 91 patients with histopathologically confirmed RCC. WGS data were analyzed for small somatic variants, copy-number alterations and structural variants. For a subgroup of patients, RNA sequencing (RNA-Seq) data could be analyzed. RNA-Seq data were clustered on immunogenic and angiogenic gene expression patterns according to a previously developed angio-immunogenic gene signature. In all patients with papillary and clear cell RCC, putative actionable drug targets were detected by WGS, of which 94% were on-label available. RNA-Seq data of clear cell and papillary RCC were clustered using a previously developed angio-immunogenic gene signature. Analyses of driver mutations and RNA-Seq data revealed clear differences among different RCC subtypes, showing the added value of WGS and RNA-Seq over clinicopathological data. By improving both histological subtyping and the selection of treatment according to actionable targets and immune signatures, WGS and RNA-Seq may improve therapeutic decision making for most patients with advanced RCC, including patients with non-clear cell RCC for whom no standard treatment is available to data. Prospective clinical trials are needed to evaluate the impact of genomic and transcriptomic diagnostics on survival outcome for advanced RCC patients.

Early on-treatment changes in circulating tumor DNA fraction and response to enzalutamide or abiraterone in metastatic castration-resistant prostate cancer

PURPOSE

Androgen receptor pathway inhibitors (ARPI) are standard of care for treatment-naive metastatic castration-resistant prostate cancer (mCRPC), but rapid resistance is common. Early identification of resistance will improve management strategies. We investigated whether changes in circulating tumor DNA (ctDNA) fraction during ARPI treatment are linked with mCRPC clinical outcomes.

EXPERIMENTAL DESIGN

Plasma cell-free DNA was collected from 81 patients with mCRPC at baseline and after 4-weeks of first-line ARPI treatment during two prospective multi-centre observational studies (NCT02426333;NCT02471469). CtDNA fraction was calculated from somatic mutations in targeted sequencing and genome copy number profiles. Samples were classified into detected vs. undetected ctDNA. Outcome measurements were progression-free survival (PFS) and overall survival (OS). Non-durable treatment response was defined as PFS ≤ 6 months.

RESULTS

CtDNA was detected in 48/81 (59%) baseline and 29/81 (36%) 4-week samples. CtDNA fraction for samples with detected ctDNA was lower at 4-weeks vs. baseline (median 5.0% vs. 14.5%, P=0.017). PFS and OS was shortest for patients with persistent ctDNA at 4 weeks (univariate hazard ratio 4.79 (95%CI, 2.62-8.77) and 5.49 (95%CI, 2.76-10.91), respectively), independent of clinical prognostic factors. For patients exhibiting change from detected to undetected ctDNA by 4-weeks, there was no significant PFS difference versus patients with baseline undetected ctDNA. CtDNA change had a positive predictive value of 88% and negative predictive value of 92% for identifying non-durable responses.

CONCLUSIONS

Early changes in ctDNA% are strongly linked to duration of first-line ARPI treatment benefit and survival in mCRPC and may inform early therapy switches or treatment intensification.

Role of multidisciplinary team meetings in implementation of chemohormonal therapy in metastatic prostate cancer in daily practice

BACKGROUND

The recommended treatment for a subset of patients with metastatic prostate cancer (mPC) changed from androgen deprivation therapy (ADT) to combinations with chemotherapy such as docetaxel. Implementation of new evidence from trials is however complex and challenging. We investigated the effect of multidisciplinary team meetings (MDTs) on adopting the newest emerging combination therapy in patients with mPC and assessed the overall survival of chemohormonal therapy in a real-world setting.

METHODS

All mPC patients diagnosed between October 2015 and April 2016 in the Netherlands were identified from the population-based Netherlands Cancer Registry (n = 962). Logistic regression analyses were performed to examine the role of patient- and tumor characteristics, with special emphasis on MDTs, on receiving chemohormonal therapy versus ADT monotherapy. Kaplan-Meier survival curves were used to assess overall survival (OS).

RESULTS

As many patients received ADT monotherapy as chemohormonal therapy (both n = 452). Being discussed in a MDT as patient, younger age, less comorbidities, a better performance status and high-volume disease were significantly associated with receiving chemohormonal therapy compared to ADT monotherapy. After adjustment for these factors, the presence of a MDT was independently associated with the administration of chemohormonal therapy (OR 2.77, 95% CI 1.68-4.59). The 2-year OS was 82.1% (95% CI: 78.5-85.6%) for patients receiving chemohormonal therapy and 59.9% (95% CI: 55.4-64.4%) for patients receiving ADT monotherapy.

CONCLUSION

Being discussed in a MDT is independently associated with the administration of chemohormonal therapy in this group of patients with mPC. This supports the hypothesis that implementation of innovative treatment options is facilitated by an organizational structure with MDTs.

CABA-V7: a prospective biomarker selected trial of cabazitaxel treatment in AR-V7 positive prostate cancer patients

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) patients with positive AR-V7 expression in their circulating tumour cells (CTCs) rarely derive benefit from abiraterone and enzalutamide.

DESIGN

We performed a prospective, multicenter, single arm phase II clinical trial (CABA-V7) in mCRPC patients previously treated with docetaxel and androgen deprivation therapy.

OBJECTIVE

In this trial, we investigated whether cabazitaxel treatment resulted in clinically meaningful PSA response rates in patients with positive CTC-based AR-V7 expression and collected liquid biopsies for genomic profiling.

RESULTS

Cabazitaxel was found to be modestly effective, with only 12% of these patients obtaining a PSA response. Genomic profiling revealed that CTC-based AR-V7 expression was not associated with other known mCRPC-associated alterations. CTC-based AR-V7 status and dichotomised CTC counts were observed as independent prognostic markers at baseline.

CONCLUSIONS

AR-V7 positivity predicted poor overall survival (OS). However, cabazitaxel-treated AR-V7 positive patients and those lacking AR-V7 positivity, who received cabazitaxel as standard of care, appeared to have similar OS. Therefore, despite the low response rate, cabazitaxel may still be an effective treatment in this poor prognosis, AR-V7 positive patient population.

Pembrolizumab versus placebo as post-nephrectomy adjuvant therapy for clear cell renal cell carcinoma (KEYNOTE-564): 30-month follow-up analysis of a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

The first interim analysis of the KEYNOTE-564 study showed improved disease-free survival with adjuvant pembrolizumab compared with placebo after surgery in patients with clear cell renal cell carcinoma at an increased risk of recurrence. The analysis reported here, with an additional 6 months of follow-up, was designed to assess longer-term efficacy and safety of pembrolizumab versus placebo, as well as additional secondary and exploratory endpoints.

METHODS

In the multicentre, randomised, double-blind, placebo-controlled, phase 3 KEYNOTE-564 trial, adults aged 18 years or older with clear cell renal cell carcinoma with an increased risk of recurrence were enrolled at 213 hospitals and cancer centres in North America, South America, Europe, Asia, and Australia. Eligible participants had an Eastern Cooperative Oncology Group performance status of 0 or 1, had undergone nephrectomy 12 weeks or less before randomisation, and had not received previous systemic therapy for advanced renal cell carcinoma. Participants were randomly assigned (1:1) via central permuted block randomisation (block size of four) to receive pembrolizumab 200 mg or placebo intravenously every 3 weeks for up to 17 cycles. Randomisation was stratified by metastatic disease status (M0 vs M1), and the M0 group was further stratified by ECOG performance status and geographical region. All participants and investigators involved in study treatment administration were masked to the treatment group assignment. The primary endpoint was disease-free survival by investigator assessment in the intention-to-treat population (all participants randomly assigned to a treatment). Safety was assessed in the safety population, comprising all participants who received at least one dose of pembrolizumab or placebo. As the primary endpoint was met at the first interim analysis, updated data are reported without p values. This study is ongoing, but no longer recruiting, and is registered with ClinicalTrials.gov, NCT03142334.

FINDINGS

Between June 30, 2017, and Sept 20, 2019, 994 participants were assigned to receive pembrolizumab (n=496) or placebo (n=498). Median follow-up, defined as the time from randomisation to data cutoff (June 14, 2021), was 30·1 months (IQR 25·7-36·7). Disease-free survival was better with pembrolizumab compared with placebo (HR 0·63 [95% CI 0·50-0·80]). Median disease-free survival was not reached in either group. The most common all-cause grade 3-4 adverse events were hypertension (in 14 [3%] of 496 participants) and increased alanine aminotransferase (in 11 [2%]) in the pembrolizumab group, and hypertension (in 13 [3%] of 498 participants) in the placebo group. Serious adverse events attributed to study treatment occurred in 59 (12%) participants in the pembrolizumab group and one (<1%) participant in the placebo group. No deaths were attributed to pembrolizumab.

INTERPRETATION

Updated results from KEYNOTE-564 support the use of adjuvant pembrolizumab monotherapy as a standard of care for participants with renal cell carcinoma with an increased risk of recurrence after nephrectomy.

FUNDING

Merck Sharp & Dohme LLC, a subsidiary of Merck & Co, Inc, Rahway, NJ, USA.

Influence of darolutamide on cabazitaxel systemic exposure

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Background: Taxane efficacy in metastatic castration-resistant prostate cancer (mCRPC) patients is limited due to resistance development. In preclinical models it has been shown that addition of the androgen receptor signalling inhibitor (ARSI) enzalutamide improves cabazitaxel efficacy. However, we have previously shown that the clinical utility of this combination is hampered by a strong CYP3A4 drug-drug interaction with enzalutamide, resulting in a 22% reduced cabazitaxel systemic exposure. Darolutamide has much weaker CYP3A4 inducing effects and therefore may affect cabazitaxel systemic exposure to a lesser extent. Methods: We investigated the influence of darolutamide on cabazitaxel plasma exposure. mCRPC patients were enrolled on cabazitaxel monotherapy (20 mg/m2 Q3W) on day 1 and received concomitant darolutamide (600 mg b.i.d.) from day 2 onwards for maximal 12 weeks. During cabazitaxel infusion on day 1, and after 6 and 12 weeks of darolutamide treatment, we measured cabazitaxel systemic exposure via Area Under the Curve from 0 to 24 hours (AUC0-24h). Results: Cabazitaxel systemic exposure in 18 patients after 6 weeks of darolutamide was not significantly different compared to prior to darolutamide treatment (AUC0-24h: -4%; 95%CI -19 – +13%; p = 0.58). Also, after 12 weeks of darolutamide treatment, cabazitaxel systemic exposure was unaltered (AUC0-24h: +4%; 95%CI -10 – +20%; p = 0.54). Darolutamide plasma concentrations were constant throughout the study (Table). Conclusions: From a pharmacokinetic perspective cabazitaxel and darolutamide can be safely combined in mCRPC patients. Our findings pave the way for testing the efficacy of this promising combination in an era of combination regimens for prostate cancer. Clinical trial information: NL8611. [Table: see text]

RNA Biomarkers as a Response Measure for Survival in Patients with Metastatic Castration-Resistant Prostate Cancer

Treatment evaluation in metastatic castration-resistant prostate cancer is challenging. There is an urgent need for biomarkers to discriminate short-term survivors from long-term survivors, shortly after treatment initiation. Thereto, the added value of early RNA biomarkers on predicting progression-free survival (PFS) and overall survival (OS) were explored. The RNA biomarkers: KLK3 mRNA, miR-375, miR-3687, and NAALADL2-AS2 were measured in 93 patients with mCRPC, before and 1 month after start of first-line abiraterone acetate or enzalutamide treatment, in two prospective clinical trials. The added value of the biomarkers to standard clinical parameters in predicting PFS and OS was tested by Harell's C-index. To test whether the biomarkers were independent markers of PFS and OS, multivariate Cox regression was used. The best prediction model for PFS and OS was formed by adding miR-375 and KLK3 (at baseline and 1 month) to standard clinical parameters. Baseline miR-375 and detectable KLK3 after 1 month of therapy were independently related to shorter PFS, which was not observed for OS. In conclusion, the addition of KLK3 and miR-375 (at baseline and 1 month) to standard clinical parameters resulted in the best prediction model for survival assessment.

Evaluation of the Khorana, PROTECHT, and 5-SNP scores for prediction of venous thromboembolism in patients with cancer

BACKGROUND

The Khorana score is a validated tool to identify cancer patients at higher risk of venous thromboembolism (VTE).

OBJECTIVE

We compared its predictive performance to that of the clinical PROTECHT and the polygenic 5-SNP scores in patients who participated in the Dutch CPCT-02 study.

PATIENTS/METHODS

Data on VTE and its risk factors were retrospectively collected for 2729 patients with advanced stage solid tumors planned for systemic cancer treatment. Patients were followed for 6 months. Overall discriminatory performance of the scores was evaluated by time-dependent c-indices. The scores were additionally evaluated dichotomously in competing risk models.

RESULTS

A total of 160 (5.9%) patients developed VTE during follow-up. Time-dependent c-indices at 6 months for the Khorana, PROTECHT, and 5-SNP scores were 0.57 (95% confidence interval [CI]: 0.55-0.60), 0.60 (95% CI: 0.57-0.62), and 0.54 (95% CI: 0.51-0.57), respectively. The dichotomous scores classified 9.6%, 16.8%, and 9.5% as high-risk, respectively. VTE risk was about 2-fold higher among high-risk patients than low-risk patients for the Khorana (subdistribution hazard ratio [SHR] 1.9, 95% CI: 1.3-3.0), PROTECHT (SHR 2.1, 95% CI: 1.5-3.0), and 5-SNP scores (SHR 1.7, 95% CI: 1.03-2.8). The sensitivity at 6 months was 16.6% (95% CI: 10.5-22.7), 28.9% (95% CI: 21.5-36.3), and 14.9% (95% CI: 8.5-21.2), respectively.

CONCLUSIONS

Performance of the PROTECHT or 5-SNP score was not superior to that of the Khorana score. The majority of cancer patients who developed VTE during 6-month follow-up were not identified by these scores. Future directions for studies on cancer-associated VTE prediction may include combined clinical-genetic scores.

Life-prolonging treatment restrictions and outcomes in patients with cancer and COVID-19: an update from the Dutch Oncology COVID-19 Consortium

Aim of the study

The coronavirus disease 2019 (COVID-19) pandemic significantly impacted cancer care. In this study, clinical patient characteristics related to COVID-19 outcomes and advanced care planning, in terms of non-oncological treatment restrictions (e.g. do-not-resuscitate codes), were studied in patients with cancer and COVID-19.

Methods

The Dutch Oncology COVID-19 Consortium registry was launched in March 2020 in 45 hospitals in the Netherlands, primarily to identify risk factors of a severe COVID-19 outcome in patients with cancer. Here, an updated analysis of the registry was performed, and treatment restrictions (e.g. do-not-intubate codes) were studied in relation to COVID-19 outcomes in patients with cancer. Oncological treatment restrictions were not taken into account.

Results

Between 27th March 2020 and 4th February 2021, 1360 patients with cancer and COVID-19 were registered. Follow-up data of 830 patients could be validated for this analysis. Overall, 230 of 830 (27.7%) patients died of COVID-19, and 60% of the remaining 600 patients with resolved COVID-19 were admitted to the hospital. Patients with haematological malignancies or lung cancer had a higher risk of a fatal outcome than other solid tumours. No correlation between anticancer therapies and the risk of a fatal COVID-19 outcome was found. In terms of end-of-life communication, 50% of all patients had restrictions regarding life-prolonging treatment (e.g. do-not-intubate codes). Most identified patients with treatment restrictions had risk factors associated with fatal COVID-19 outcome.

Conclusion

There was no evidence of a negative impact of anticancer therapies on COVID-19 outcomes. Timely end-of-life communication as part of advanced care planning could save patients from prolonged suffering and decrease burden in intensive care units. Early discussion of treatment restrictions should therefore be part of routine oncological care, especially during the COVID-19 pandemic.

Patients with Biallelic BRCA1/2 Inactivation Respond to Olaparib Treatment Across Histologic Tumor Types

PURPOSE

To assess the efficacy of olaparib, a PARP inhibitor (PARPi) in patients with tumors with BRCA1/2 mutations, regardless of histologic tumor type.

PATIENTS AND METHODS

Patients with treatment-refractory BRCA1/2-mutated cancer were included for treatment with off-label olaparib 300 mg twice daily until disease progression or unacceptable toxicity. In Drug Rediscovery Protocol (DRUP), patients with treatment-refractory solid malignancies receive off-label drugs based on tumor molecular profiles while whole-genome sequencing (WGS) is performed on baseline tumor biopsies. The primary endpoint was clinical benefit (CB; defined as objective response or stable disease ≥ 16 weeks according to RECIST 1.1). Per protocol patients were enrolled using a Simon-like two-stage model.

RESULTS

Twenty-four evaluable patients with nine different tumor types harboring BRCA1/2 mutations were included, 58% had CB from treatment with olaparib. CB was observed in patients with complete loss of function (LoF) of BRCA1/2, while 73% of patients with biallelic BRCA LoF had CB. In 17 patients with and seven without current labeled indication, 10 and four patients had CB, respectively. Treatment resistance in four patients with biallelic loss might be explained by an additional oncogenic driver which was discovered by WGS, including Wnt pathway activation, FGFR amplification, and CDKN2A loss, in three tumor types.

CONCLUSIONS

These data indicate that using PARPis is a promising treatment strategy for patients with non-BRCA-associated histologies harboring biallelic BRCA LoF. WGS allows to accurately detect complete LoF of BRCA and homologous repair deficiency (HRD) signature as well as oncogenic drivers that may contribute to resistance, using a single assay.

Anti-PD-1 Efficacy in Patients with Metastatic Urothelial Cancer Associates with Intratumoral Juxtaposition of T Helper-Type 1 and CD8+ T cells

PURPOSE

PD-1 inhibition results in durable antitumor responses in a proportion of patients with metastatic urothelial cancer (mUC). The majority of patients, however, do not experience clinical benefit. In this study, we aimed to identify early changes in T-cell subsets that underlie anti-PD-1 efficacy in patients with mUC.

EXPERIMENTAL DESIGN

Paired samples were collected from peripheral blood, plasma, and metastatic lesions of 56 patients with mUC at baseline and weeks 6 and 12 after initiating pembrolizumab treatment (200 mg intravenously, every 3 weeks). Samples were analyzed using multiplex flow cytometry, ELISA, and in situ stainings, including cellular network analysis. Treatment response was evaluated as best overall response according to RECIST v1.1, and patients were classified as responder (complete or partial response) or nonresponder (progressive disease).

RESULTS

In responders, baseline fractions of CD4⁺ T cells expressing cosignaling receptors were higher compared with nonresponders. The fraction of circulating PD-1⁺ CD4⁺ T cells decreased at weeks 6 and 12, whereas the fraction of 4-1BB⁺ CD28⁺ CD4⁺ T cells increased at week 12. In metastatic lesions of responders, the baseline density of T helper-type 1 (Th1) cells, defined as T-bet⁺ CD4⁺ T cells, was higher as compared to non-responders. Upon treatment, Th1 cells became localized in close proximity to CD8⁺ T cells, CD11b⁺ myeloid cells, and tumor cells.

CONCLUSIONS

A decrease in the fraction of circulating PD-1⁺ CD4⁺ T cells, and juxtaposition of Th1, CD8⁺, and myeloid cells was associated with response to anti-PD-1 treatment in patients with mUC.

Prospective Evaluation of a Circulating Tumor Cell Sensitivity Profile to Predict Response to Cisplatin Chemotherapy in Metastatic Breast Cancer Patients

Background

Cisplatin (cDDP) has regained interest for metastatic breast cancer (MBC) patients, given the platinum sensitivity in subtypes and better manageable toxicity. Here, the primary aim was to determine whether molecular characteristics of circulating tumor cells (CTCs) could identify patients responding to cDDP and to describe the outcomes to cDDP monotherapy in a large group of MBC patients pretreated with anthracycline- and taxane-based treatments.

Methods

Based on cell line data, a CTC-cDDP-sensitivity profile was generated. Applying an A’Herns single-stage phase II design, further investigation was considered worthwhile if 5/10 patients with a favorable profile responded to cDDP. Patients received 70mg/m² cDDP every three weeks, CTCs were enumerated and the CTC-cDDP-sensitivity profile was determined. In total, 65 heavily pretreated MBC patients (77% received ≥2 lines of previous chemotherapy for MBC) were eligible for the per-protocol analysis. Primary endpoint was response rate, secondary endpoints included best observed response, progression-free survival (PFS) and overall survival (OS).

Results

The best observed response during cDDP therapy was a partial response in 7% and stable disease in 56% of the patients. None of the patients with a favorable CTC-cDDP-sensitivity profile had a response. The median baseline CTC count was 8 (range 0-3254). Patients with <5 CTCs had a better PFS and OS than patients with ≥5 CTCs (median PFS 4.5 months (95%CI 2.38-6.62) vs. 2.1 months [(95%CI 1.34-2.80)(p=0.009)] and median OS 13.1 months (95%CI 9.89-16.33) vs. 5.6 months [(95%CI 3.60-7.64)(p=0.003)]. No other factors than CTC count were associated with outcome to cDDP therapy, including triple-negative breast cancer versus ER-positive tumors.

Conclusions

The CTC-cDDP-sensitivity profile was unable to select patients responding to cDDP monotherapy. In an unselected group of heavily pretreated MBC patients, cDDP yields outcomes comparable to other chemotherapeutic regimens for heavily pretreated MBC patients. CTC count was the only factor associated with outcome in these patients.

Clinical Trial Registration

(https://www.trialregister.nl/trial/3885, identifier NTR4046)

11-Ketotestosterone is the predominant active androgen in prostate cancer patients after castration

BACKGROUND

Continued androgen receptor (AR) signaling constitutes a key target for treatment in metastatic castration-resistant prostate cancer (CRPC). Studies have identified 11-ketotestosterone (11KT) as a potent AR agonist, but it is unknown if 11KT is present at physiologically relevant concentrations in patients with CRPC to drive AR activation. The goal of this study was to investigate the circulating steroid metabolome including all active androgens in patients with CRPC.

METHODS

Patients with metastatic CRPC (n = 29) starting a new line of systemic therapy were included. Sequential plasma samples were obtained for measurement of circulating steroid concentrations by multisteroid profiling employing liquid chromatography–tandem mass spectrometry. Metastatic tumor biopsy samples were obtained at baseline and subjected to RNA sequencing.

RESULTS

11KT was the most abundant circulating active androgen in 97% of patients with CRPC (median 0.39 nmol/L, range: 0.03–2.39 nmol/L), constituting 60% (IQR 43%–79%) of the total active androgen (TA) pool. Treatment with glucocorticoids reduced 11KT by 84% (49%–89%) and testosterone by 68% (38%–79%). Circulating TA concentrations at baseline were associated with a distinct intratumor gene expression signature comprising AR-regulated genes.

CONCLUSION

The potent AR agonist 11KT is the predominant circulating active androgen in patients with CRPC and, therefore, one of the potential drivers of AR activation in CRPC. Assessment of androgen status should be extended to include 11KT, as current clinical approaches likely underestimate androgen abundance in patients with CRPC.

TRIAL REGISTRATION

Netherlands Trial Register: NL5625 (NTR5732).

FUNDING

Daniel den Hoed Foundation and Wellcome Trust (Investigator Award WT209492/Z/17/Z).

A phase III trial of docetaxel versus docetaxel and radium-223 (Ra-223) in patients with metastatic castration-resistant prostate cancer (mCRPC): DORA

TPS5091

Background: Ra-223, a bone-targeted alpha therapy, prolongs survival in patients (pts) with symptomatic mCRPC to bone. Docetaxel targets microtubule trafficking improving survival in the mCRPC and metastatic hormone-sensitive settings. We hypothesized that simultaneously targeting the tumor and bone compartment yields superior outcomes than targeting either alone. We previously determined the dose and schedule of co-administering Ra-223 + docetaxel in a randomized phase I/IIa trial. The combination appeared to have improved declines in prostate specific antigen (PSA) and bone markers, delayed PSA progression, and was better tolerated (with adjusted dose/schedule) relative to standard docetaxel alone. We are now conducting a phase III study to determine the clinical benefit of the regimen. Methods: Randomization (1:1) of 738 men with mCRPC to docetaxel or docetaxel + Ra-223 is planned with a projected hazard ratio for treatment effect (15 vs 20 months median survival) of 0.75. Pts with ≥2 bone lesions and progression by Prostate Cancer Working Group 3 criteria are eligible. Other key inclusion criteria are an Eastern Cooperative Oncology Group performance status of 0–1 and normal organ function. Key exclusion criteria are: use of anticancer therapy ≤4 weeks (wks) before randomization and use of bone-seeking radiopharmaceuticals or chemotherapy in the castration-resistant setting, and bulky visceral metastases (≥3 lung and/or liver or a lesion ≥2 cm in the previous 8 wks). Subjects receive docetaxel 75 mg/m2 IV q3w for 10 doses or docetaxel 60 mg/m2 IV q3w for 10 doses + Ra-223 55 kBq/kg IV q6w for 6 doses. The primary endpoint is overall survival. Secondary and exploratory endpoints include: radiographic progression-free survival, symptomatic skeletal event-free survival, safety, markers of bone metabolism, alterations in circulating tumor cells and DNA, detection of androgen-receptor splice variant 7, changes in automated bone scan index (aBSI), and assessment of patient-reported outcome instruments (FACT-P, Brief Pain Inventory, Brief Fatigue Inventory). The study is open at 32 sites in the US and Netherlands and has 170 subjects enrolled. The study is sponsored by Memorial Sloan Kettering Cancer Center, and managed by the Prostate Cancer Clinical Trials Consortium. Clinical trial information: NCT03574571.

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)

5059

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.

Generating human prostate cancer organoids from leukapheresis enriched circulating tumour cells

BACKGROUND

Circulating tumour cell (CTC)-derived organoids have the potential to provide a powerful tool for personalised cancer therapy but are restrained by low CTC numbers provided by blood samples. Here, we used diagnostic leukapheresis (DLA) to enrich CTCs from patients with metastatic prostate cancer (mPCa) and explored whether organoids provide a platform for ex vivo treatment modelling.

METHODS

We prospectively screened 102 patients with mPCa and performed DLA in 40 patients with ≥5 CTCs/7.5 mL blood. We enriched CTCs from DLA using white blood cell (WBC) depletion alone or combined with EpCAM selection. The enriched CTC samples were cultured in 3D to obtain organoids and used for downstream analyses.

RESULTS

The DLA procedure resulted in a median yield of 5312 CTCs as compared with 22 CTCs in 7.5 mL of blood. Using WBC depletion, we recovered 46% of the CTCs, which reduced to 12% with subsequent EpCAM selection. From the isolated and enriched CTC samples, organoid expansion succeeded in 35%. Successful organoid cultures contained significantly higher CTC numbers at initiation. Moreover, we performed treatment modelling in one organoid cell line and identified substantial tumour heterogeneity in CTCs using single cell DNA sequencing.

CONCLUSIONS

DLA is an efficient method to enrich CTCs, although the modest success rate of culturing CTCs precludes large scale clinical application. Our data do suggest that DLA and subsequent processing provides a rich source of viable tumour cells. Therefore, DLA offers a promising alternative to biopsy procedures to obtain sufficient number of tumour cells to study sequential samples in patients with mPCa.

TRIAL REGISTRATION NUMBER

NL6019.

Prognostic Value of Novel Liquid Biomarkers in Patients with Metastatic Castration-Resistant Prostate Cancer Treated with Enzalutamide: A Prospective Observational Study

BACKGROUND

Several treatment options were recently added for metastatic castration-resistant prostate cancer (mCRPC). However, response to therapy is variable, and biomarkers that can guide treatment selection and response evaluation are lacking. Circulating RNAs are a promising source of biomarkers. We explored messenger RNAs (mRNAs), microRNAs (miRNAs), and long noncoding RNAs (lncRNAs) as potential biomarkers in liquid biopsies of patients with mCRPC treated with enzalutamide.

METHODS

Forty patients were included in this prospective multicenter observational study. Whole blood was drawn at baseline and 1, 3, and 6 months after start of therapy. Four mRNAs, 6 miRNAs, and 5 lncRNAs were analyzed by quantitative PCR. RNA levels in 30 healthy individuals were used as controls. RNA expression data were analyzed by Kaplan-Meier and Cox regression analyses, and the primary end point was progression-free survival. Clinical factors were included in the multivariable Cox regression analysis.

RESULTS

Levels of 2 miRNAs, miR-375 and miR-3687, and 1 lncRNA, N-acetylated alpha-linked acidic dipeptidase like 2 antisense RNA 2 (NAALADL2-AS2), were more than 2-fold higher in patients with mCRPC compared with healthy volunteers. Patients with higher levels of miR-375 or miR-3687 showed a shorter time to progression. Patients with higher levels of NAALADL2-AS2 showed a longer time to progression. In the multivariable Cox regression analysis, higher miR-375, miR-3687 and serum prostate-specific antigen concentrations were shown to be independent predictors for shorter time to progression.

CONCLUSIONS

We identified miR-3687 as a novel prognostic marker for response in patients with CRPC treated with enzalutamide, and we confirmed the prognostic value of miR-375.

The impact of a 1-hour time interval between pazopanib and subsequent intake of gastric acid suppressants on pazopanib exposure

Co‐treatment with gastric acid suppressants (GAS) in patients taking anticancer drugs that exhibit pH‐dependant absorption may lead to decreased drug exposure and may hamper drug efficacy. In our study, we investigated whether a 1‐hour time interval between subsequent intake of pazopanib and GAS could mitigate this negative effect on drug exposure. We performed an observational study in which we collected the first steady‐state pazopanib trough concentration (C_min) levels from patients treated with pazopanib 800 mg once daily (OD) taken fasted or pazopanib 600 mg OD taken with food. All patients were advised to take GAS 1 hour after pazopanib. Patients were grouped based on the use of GAS and the geometric (GM) C_min levels were compared between groups for each dose regimen. Additionally, the percentage of patients with exposure below the target threshold of 20.5 mg/L and the effect of the type of PPI was explored. The GM C_min levels were lower in GAS users vs non‐GAS users for both the 800 and 600 mg cohorts (23.7 mg/L [95% confidence interval [CI]: 21.1‐26.7] vs 28.2 mg/L [95% CI: 25.9‐30.5], P = .015 and 26.0 mg/L [95% CI: 22.4‐30.3] vs 33.5 mg/L [95% CI: 30.3‐37.1], P = .006). Subtherapeutic exposure was more prevalent in GAS users vs non‐GAS users (33.3% vs 19.5% and 29.6% vs 14%). Sub‐analysis showed lower GM pazopanib C_min in patients who received omeprazole, while minimal difference was observed in those receiving pantoprazole compared to non‐users. Our research showed that a 1‐hour time interval between intake of pazopanib and GAS did not mitigate the negative effect of GAS on pazopanib exposure and may hamper pazopanib efficacy.

Abstract 3919: Liquid biopsy derived organoids as a potential platform for personalized cancer therapy in metastatic prostate cancer

Introduction

Circulating tumor cells (CTCs) can serve as a source of metastatic tumor material, however their low numbers often limit downstream applications. Diagnostic leukapheresis (DLA) has been shown to substantially increase CTC yield. In this study we isolated CTCs from metastatic prostate cancer (mPCa) patients by DLA to propagate them in vitro as organoid cultures. Furthermore, tumor-derived organoids were used as a model for drug discovery and sensitivity-screening, thereby exploring potential treatment selection.

Methods

We included 44 mPCa patients into the study and 18 were selected for DLA, based on the presence of ≥5 CTCs/ 7.5 mL blood. We optimized the DLA procedure by comparing low versus high density settings and their impact on CTC isolation efficacy. As the DLA product contains a median of 8.6*10^9 white blood cells (WBC), stringent enrichment methods are needed. CTC enrichment from DLA product was performed by antibody-based WBC depletion alone, or combined with subsequent EpCAM based enrichment. Enriched CTC fractions were cultured in vitro under optimized conditions, to initiate organoid expansion.

Results

We show that DLA is a safe and efficient method to collect large amounts of CTCs from mPCa patients. With optimized DLA settings we were able to improve CTC enrichment and observed a non-significant increase in CTC yield from DLA (median CTC recovery 15339 vs 5796, P=0.125). WBC depletion alone was found to reduce WBCs by ~2000-fold while retaining &gt;50% of the CTCs, resulting in a WBC to CTC ratio of 545:1. We were able to culture and confirm CTC-derived organoids in 9/18 samples, including one organoid cell line, EMC-PCa-41. Whole Genome Sequencing (WGS) of EMC-PCa-41 revealed a triploid genome characterized by focal amplification of AR, a TMPRSS2-ERG fusion, a PTEN deletion and multiple inter-chromosomal rearrangements. Next we determined copy number profiles in single CTCs and matched organoids from two patients using shallow WGS. These data confirm prior data that CTCs represent the inherent intra-patient heterogeneity and organoids resemble CTCs from the original DLA product. Moreover, we performed an in vitro drug screen with the organoid cell line EMC-PCa-41, and found that it has a limited response to Enzalutamide, which correlated with the relatively short response to Enzalutamide that was observed in the patient.

Conclusion

Overall our study demonstrates that DLA provides a high CTC yield which enables short-term organoid cultures that preserve the genomic hallmarks of prostate cancer. Viable CTCs obtained by DLA may serve as a (personalized) drug screening system in metastatic prostate cancer.

Citation Format: Lisanne Mout, Lisanne F. van Dessel, Jaco Kraan, Anouk C. de Jong, Rui P. Neves, Sigrun Erkens-Schulze, Anieta M. Siewerts, Job van Riet, Ronald de Wit, Stefan Sleijfer, Paul Hamberg, Yorick Sandberg, Peter A. te Boekhorst, Harmen J. van de Werken, John W. Martens, Nikolas H. Stoecklein, Wytske M. van Weerden, Martijn P. Lolkema. Liquid biopsy derived organoids as a potential platform for personalized cancer therapy in metastatic prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3919.

Urinary incontinence and erectile dysfunction in patients with localized or locally advanced prostate cancer: A nationwide observational study

BACKGROUND

Although urinary adverse events after treatment of prostate cancer (CaP) are common, population-based studies on functional outcomes are scarce. The aim of this study is to evaluate the occurrence of urinary incontinence (UI) and erectile dysfunction (ED) in daily clinical practice using a nationwide Dutch cohort of patients with localized or locally advanced CaP.

BASIC PROCEDURES

Patients were invited to complete the EPIC-26 questionnaire before treatment (baseline) and at 12 and 24 months after diagnosis. We calculated the mean EPIC-26 domain scores, stratified by treatment modality (i.e., radical prostatectomy, external radiotherapy, and no active treatment), and the proportions of patients with UI (defined as ≥ 2 pads per day) and ED (defined as erections not firm enough for sexual intercourse). Logistic regression modeling was used to explore the factors related to UI and ED after surgery.

MAIN FINDINGS

In total 1,759 patients participated in this study. Patients undergoing radical prostatectomy experienced clinically relevant worsening in the urinary incontinence domain. After excluding patients who reported UI at baseline, 15% of patients with prostatectomy reported UI 24 months after diagnosis. Only comorbidity was associated with UI in surgically treated patients. Regardless of treatment, patients reported a clinically significant reduced sexual functioning over time. Before treatment, 54% of patients reported ED. Among the 46% remaining patients, 87% of patients treated with radical prostatectomy reported ED 24 months after diagnosis, 41% after radiotherapy, and 46% in patients without active treatment. Bilateral nerve-sparing surgery was the only factor associated with ED after 24 months.

PRINCIPAL CONCLUSIONS

UI and ED frequently occur in patients with localized and locally advanced CaP, in particular after radical prostatectomy. The higher occurrence rate of UI and ED, compared with clinical trial participants, supports the importance of real-world data, which can be used for local treatment recommendations and patient information, but also to evaluate effects of future initiatives, such as treatment centralization and research aimed at improving functional outcomes.

Early response marker during pembrolizumab treatment in metastatic urothelial cancer: Temporal shift in peripheral CD4 T cells expressing chemokine receptors

5033

Background: Approval of PD1 blockade greatly improved treatment possibilities for patients with platinum-resistant metastatic urothelial cancer (mUC), however the current response rate for pembrolizumab is less than 25%. Since PD-L1 expression does not have predictive value in this setting, the aim of this study was to identify new markers to improve patient selection. Methods: Between Sept 2017 and Jan 2020, 84 mUC patients received pembrolizumab in a prospective biomarker discovery study (NCT03263039). Peripheral blood samples (n = 22) taken prior to and at 6 and 12 weeks after start of treatment were analyzed for frequencies of CD4 and CD8 T cells expressing co-inhibitory, co-stimulatory and chemokine receptors using multiplex flow cytometry. Plasma chemokine levels were determined using ELISA (n = 38), and fresh tumor biopsies obtained prior to and during treatment (n = 26) were analyzed for densities and phenotypes of T cells using multiplex immunofluorescence staining. T cell receptor clonality was analyzed in peripheral blood (n = 10) and tumor biopsies (n = 6) using RNA sequencing. Patients were classified as responder (complete or partial response) or non-responder (progressive disease) according to RECIST v1.1 after 12 weeks of treatment. Results: Longitudinal sampling revealed that upon treatment the frequency of CXCR3+ CD4 T cells decreased in responders, whereas the frequency of CXCR3+ CCR1+ CD4 T cells drastically increased in non-responders. Before treatment, the frequency of CD4 T cells co-expressing CXCR3 and CCR1 was already decreased in responders. Notably, in responders, the treatment-related decrease in frequency of CD4 T cells expressing chemokine receptors was accompanied by a decrease in the frequency of CD4 T cells expressing the co-inhibitory receptor PD1, whereas an increase in the frequency of CD4 T cells expressing the co-stimulatory receptor 4-1BB was observed. These findings will be complemented with chemokine levels in plasma, contexture of T cells in tumor biopsies, and T cell receptor clonality analysis. Conclusions: mUC patients responding to pembrolizumab treatment demonstrated an on-treatment decrease in frequency of CD4 T cells expressing chemokine receptors that is accompanied by a changed frequency of co-signaling receptor expressing CD4 T cells. These data show that dynamic immune phenotyping can distinguish effective from less effective immune activation by pembrolizumab, and may provide early markers for benefit from PD1 blockade in mUC patients.

68Ga-PSMA-Guided Bone Biopsies for Molecular Diagnostics in Patients with Metastatic Prostate Cancer

For individual treatment decisions in patients with metastatic prostate cancer (mPC), molecular diagnostics are increasingly used. Bone metastases are frequently the only source for obtaining metastatic tumor tissue. However, the success rate of CT-guided bone biopsies for molecular analyses in mPC patients is approximately only 40%. PET using ⁶⁸Ga prostate-specific membrane antigen (⁶⁸Ga-PSMA) is a promising tool to improve the harvest rate of bone biopsies for molecular analyses. The aim of this study was to determine the success rate of ⁶⁸Ga-PSMA-guided bone biopsies for molecular diagnostics in mPC patients. Methods: Within a prospective multicenter whole-genome sequencing trial (NCT01855477), 69 mPC patients underwent ⁶⁸Ga-PSMA PET/CT before bone biopsy. The primary endpoint was the success rate (tumor percentage ≥ 30%) of ⁶⁸Ga-PSMA-guided bone biopsies. At biopsy sites, ⁶⁸Ga-PSMA uptake was quantified using rigid-body image registration of ⁶⁸Ga-PSMA PET/CT and interventional CT. Actionable somatic alterations were identified. Results: The success rate of ⁶⁸Ga-PSMA-guided biopsies for molecular analyses was 70%. At biopsy sites categorized as positive, inconclusive, or negative for ⁶⁸Ga-PSMA uptake, 70%, 64%, and 36% of biopsies were tumor-positive (≥30%), respectively (P = 0.0610). In tumor-positive biopsies, ⁶⁸Ga-PSMA uptake was significantly higher (P = 0.008), whereas radiodensity was significantly lower (P = 0.006). With an area under the curve of 0.84 and 0.70, both ⁶⁸Ga-PSMA uptake (SUV_max) and radiodensity (mean Hounsfield units) were strong predictors for a positive biopsy. Actionable somatic alterations were detected in 73% of the sequenced biopsies. Conclusion: In patients with mPC, ⁶⁸Ga-PSMA PET/CT improves the success rate of CT-guided bone biopsies for molecular analyses, thereby identifying actionable somatic alterations in more patients. Therefore, ⁶⁸Ga-PSMA PET/CT may be considered for guidance of bone biopsies in both clinical practice and clinical trials.

CASSIOPE: A real-world study assessing the use of cabozantinib for the treatment of advanced renal cell carcinoma (aRCC) after vascular endothelial growth factor (VEGF)-targeted therapy in Europe

TPS770

Background: Cabozantinib, an inhibitor of multiple receptor tyrosine kinases including VEGF receptor 2, and MET and AXL receptors, is approved for the treatment of aRCC in the USA and, in Europe, in treatment-naïve patients with intermediate or poor risk, as well as following VEGF-targeted therapy. The METEOR trial investigated cabozantinib as second-line (2L) or later-line therapy and showed improved progression-free survival (PFS), objective response rate and overall survival vs everolimus. Adverse events (AEs) associated with cabozantinib were generally manageable in METEOR; dose interruptions and reductions occurred in 70% and 60% of patients, respectively. Here we present the design of the CASSIOPE study which aims to assess the real-life use of cabozantinib as 2L or third- or later-line (≥ 3L) therapy for aRCC. Methods: CASSIOPE is an ongoing, European, prospective, non-interventional study in adults with aRCC who have received ≥ 1 prior VEGF-targeted therapy and are initiating cabozantinib as 2L or ≥ 3L therapy according to Summary of Product Characteristics. The primary endpoint is the proportion of patients with dose modifications (interruption, reduction or discontinuation) due to AEs. Secondary endpoints include additional drug utilization parameters, effectiveness (overall best response, PFS), and healthcare resource utilization associated with managing treatment-related AEs. Overall, 680 patients (340 on 2L therapy; 340 on ≥ 3L therapy) will be enrolled to assess the 2-sided 95% confidence interval of the primary endpoint with a precision of ± 5%, assuming a 75% dose modification rate and ≤15% of starting doses lower than 60 mg. Visits will be based on the site's clinical practice, with a maximum follow-up of 12 months after treatment initiation, even if treatment is continued. Data collection started in April 2018. As of 9 October 2019, 336 patients have been enrolled. The overall study duration is expected to be 36 months. An interim analysis is planned when ≥ 340 patients have completed ≥ 3 months follow-up from treatment initiation. The study is funded by Ipsen Pharma. Clinical trial information: NCT03419572; EUPAS19464.

A prospective observational registry evaluating clinical outcomes of Radium-223 treatment in a nonstudy population

The ALSYMPCA study established a 3.6 month Overall Survival (OS) benefit in metastatic Castration Resistant Prostate Cancer (mCRPC) patients treated with Radium-223 dichloride (Ra-223) over placebo. Here we report clinical outcomes of Ra-223 treatment in a nonstudy population. In this prospective registry, patients from 20 Dutch hospitals were included prior to Ra-223 treatment. Clinical parameters collected included previous treatments and Adverse Events. Primary outcome was 6 months Symptomatic Skeletal Event (SSE)-free survival, while secondary outcomes included Progression-Free Survival (PFS) and Overall Survival (OS). Of the 305 patients included, 300 were evaluable. The mean age was 73.6 years, 90% had ≥6 bone metastases and 74.1% were pretreated with Docetaxel, 19.5% with Cabazitaxel and 80.5% with Abiraterone and/or Enzalutamide. Of all patients, 96.7% were treated with Ra-223 and received a median of 5 cycles. After a median follow-up of 13.2 months, 6 months SSE-free survival rate was 83%, median PFS was 5.1 months and median OS was 15.2 months. Six months SSE-free survival rate and OS were comparable with those reported in ALSYMPCA. "Previous Cabazitaxel treatment" and "bone-only metastases" were independent predictors of a shorter and longer PFS, respectively, while above-median LDH and "bone-only metastases" were independent predictors of shorter and longer OS, respectively. Toxicity was similar as reported in the ALSYMPCA trial. These results suggest that in a nonstudy population, Ra-223 treatment is well-tolerated, equally effective as in the ALSYMPCA population and that patients not previously treated with Cabazitaxel benefit most from Ra-223.

The genomic landscape of metastatic castration-resistant prostate cancers reveals multiple distinct genotypes with potential clinical impact

Metastatic castration-resistant prostate cancer (mCRPC) has a highly complex genomic landscape. With the recent development of novel treatments, accurate stratification strategies are needed. Here we present the whole-genome sequencing (WGS) analysis of fresh-frozen metastatic biopsies from 197 mCRPC patients. Using unsupervised clustering based on genomic features, we define eight distinct genomic clusters. We observe potentially clinically relevant genotypes, including microsatellite instability (MSI), homologous recombination deficiency (HRD) enriched with genomic deletions and BRCA2 aberrations, a tandem duplication genotype associated with CDK12-/- and a chromothripsis-enriched subgroup. Our data suggests that stratification on WGS characteristics may improve identification of MSI, CDK12-/- and HRD patients. From WGS and ChIP-seq data, we show the potential relevance of recurrent alterations in non-coding regions identified with WGS and highlight the central role of AR signaling in tumor progression. These data underline the potential value of using WGS to accurately stratify mCRPC patients into clinically actionable subgroups.

Variation in the Prescription of Androgen Deprivation Therapy in Intermediate- and High-risk Prostate Cancer Patients Treated with Radiotherapy in the Netherlands, and Adherence to European Association of Urology Guidelines: A Population-based Study

BACKGROUND

According to (inter-)national guidelines, (neo-)adjuvant and concurrent androgen deprivation therapy (ADT) in combination with external beam radiotherapy (EBRT) is optional for intermediate-risk prostate cancer (PCa) patients and is the recommended standard treatment for high-risk PCa patients.

OBJECTIVE

The aim of this study is to provide insight into the prescription of ADT in intermediate- and high-risk PCa patients treated with EBRT in the Netherlands, and to evaluate adherence to European Association of Urology guidelines and factors affecting prescription.

DESIGN, SETTING, AND PARTICIPANTS

All intermediate- and high-risk PCa patients between October 2015 and April 2016 were identified through the population-based Netherlands Cancer Registry. Variation in the prescription of ADT in patients with EBRT was evaluated. Multivariable multilevel logistic regression analyses were performed to determine the probability of ADT and to examine the role of patient-, tumour-, and hospital-related factors.

RESULTS AND LIMITATIONS

Overall, 29% of patients with intermediate-risk PCa received ADT varying from 3% to 73% between institutions. From the multivariable regression analysis, higher Gleason grade, magnetic resonance imaging, and computed tomography (CT)-positron-emission tomography/CT prior to radiotherapy appeared to be associated with increased prescription of ADT. Among high-risk patients, 83% received ADT, varying from 57% to 100% between departments. A higher prostate-specific antigen level, more advanced tumour stage, and a higher Gleason grade were associated with increased prescription.

CONCLUSIONS

Less than one-third of intermediate-risk PCa patients treated with EBRT receive ADT. The variation in the prescription of ADT between different institutions is substantial. This suggests that the prescription is largely dependent on different institutional policies. The guideline adherence in high-risk PCa is fairly good, as the vast majority of patients received ADT as recommended. However, given the clear recommendations in the guidelines, adherence could be improved.

PATIENT SUMMARY

In this review, we looked at the variation of hormonal treatment in intermediate- and high-risk prostate cancer patients. We found substantial variation between institutions.

Associations between AR-V7 status in circulating tumour cells, circulating tumour cell count and survival in men with metastatic castration-resistant prostate cancer

BACKGROUND

The interpretation of the presence of AR-V7 in circulating tumour cells (CTCs) in men with metastatic castration-resistant prostate cancer (mCRPC) remains to be elucidated. AR-V7 may hold promise as a predictive biomarker, but there may be prognostic impact of AR-V7 positivity as well. To investigate the clinical value of AR-V7, we determined whether AR-V7 detection in CTCs in patients with mCRPC is associated with CTC counts and survival.

METHODS

Between December 2011 and January 2019, three prospective clinical trials collected clinical data of patients with mCRPC, who progressed after docetaxel and/or enzalutamide or abiraterone. Baseline (and follow-up) blood samples were withdrawn determining CTC count and AR-V7 expression. The majority of patients started cabazitaxel as the next line of treatment after AR-V7 characterisation.

RESULTS

A total of 127 samples were evaluable for the analysis of CTC count versus AR-V7 status. Although an association was observed between AR-V7 and CTC count in all patients with mCRPC (p = 0.017), no such association was found in the prognostic unfavourable subgroup of patients with ≥5 CTCs. After adjusting for clinical prognostic factors, AR-V7 expression in CTCs was not associated with overall survival (hazard ratio = 1.33, 95% confidence interval = 0.81-2.15, p = 0.25).

CONCLUSION

We found that AR-V7 expression in CTCs had no additional prognostic value in patients with mCRPC, mostly treated with cabazitaxel. In patients with mCRPC with a predefined worse prognosis of a higher CTC count (≥5), a predictive biomarker is an important unmet medical need. Prospective trials should investigate whether AR-V7 detection in CTCs may guide treatment selection for these adverse prognosis patients.

A prospective phase I multicentre randomized cross-over pharmacokinetic study to determine the effect of food on abiraterone pharmacokinetics

Purpose

Abiraterone acetate is used at a fixed oral dose of 1000 mg once daily (OD) taken fasted. By administering abiraterone acetate with food, a reduced dose can potentially be given while maintaining equivalent abiraterone exposure. Moreover, administering abiraterone acetate with a breakfast is considered more patient friendly. The aim of this study was to establish the bio-equivalent lower dose of abiraterone when taken with a continental breakfast (CB) compared to the standard intake of 1000 mg OD fasted.

Methods

In this phase I, randomized cross-over, multi-center study, abiraterone pharmacokinetics (PK) were evaluated in patients with metastatic castration-resistant prostate cancer who were treated for 14 days with 1000 mg abiraterone acetate taken fasted, followed by 14 days of treatment with 500 mg taken with a CB.

Results

14 patients were enrolled into the study, of whom 12 were eligible for PK analysis. The geometric mean ratio (GMR) (fed/fasted) was 0.88 (90% CI 0.73–1.07) for area-under-the-curve (AUC_0–24h), 1.03 (90% CI 0.79–1.34) for C_max and 0.81 (90% CI 0.60–1.10) for C_trough, respectively. High inter-patient variability (> 50%) was found for all PK parameters under both intake conditions. Patients seemed to be slightly more satisfied about the intake of 500 mg abiraterone acetate when taken with a CB compared to 1000 mg fasted.

Conclusion

In conclusion, a bioequivalent lower dose of abiraterone taken with food could not be established in our study. Although based on the absence of a exposure–toxicity relationship, the strict bioequivalence margins as defined by the FDA guidelines could be applied more flexible for abiraterone. Information on the effect of food on abiraterone pharmacokinetics as presented in our study can be used for patients with difficulties taken their medication fasted.

Electronic supplementary material

The online version of this article (10.1007/s00280-019-03952-w) contains supplementary material, which is available to authorized users.

Circulating Tumor Cell Enumeration and Characterization in Metastatic Castration-Resistant Prostate Cancer Patients Treated with Cabazitaxel

(1) Background: Markers identifying which patients with metastatic, castration-resistant prostate cancer (mCRPC) will benefit from cabazitaxel therapy are currently lacking. Therefore, the aim of this study was to identify markers associated with outcome to cabazitaxel therapy based on counts and gene expression profiles of circulating tumor cells (CTCs). (2) Methods: From 120 mCRPC patients, CellSearch enriched CTCs were obtained at baseline and after 6 weeks of cabazitaxel therapy. Furthermore, 91 genes associated with prostate cancer were measured in mRNA of these CTCs. (3) Results: In 114 mCRPC patients with an evaluable CTC count, the CTC count was independently associated with poor progression-free survival (PFS) and overall survival (OS) in multivariable analysis with other commonly used variables associated with outcome in mCRPC (age, prostate specific antigen (PSA), alkaline phosphatase, lactate dehydrogenase (LDH), albumin, hemoglobin), together with alkaline phosphatase and hemoglobin. A five-gene expression profile was generated to predict for outcome to cabazitaxel therapy. However, even though this signature was associated with OS in univariate analysis, this was not the case in the multivariate analysis for OS nor for PFS. (4) Conclusion: The established five-gene expression profile in CTCs was not independently associated with PFS nor OS. However, along with alkaline phosphatase and hemoglobin, CTC-count is independently associated with PFS and OS in mCRPC patients who are treated with cabazitaxel.

AR splice variants in circulating tumor cells of patients with castration-resistant prostate cancer: relation with outcome to cabazitaxel

The androgen receptor splice variant (AR-V) 7 in circulating tumor cells (CTCs) is a predictor for resistance to anti-AR-targeted treatment, but not to taxane-based chemotherapy in metastatic castration-resistant prostate cancer (mCRPC). In this study, we investigated whether the presence of two constitutively active variants (AR-V3, AR-V7) and two other conditionally activated variants (AR-V1, AR-V9) vs full-length androgen receptor (AR-FL) measured in CTCs from patients with mCRPC were associated with outcome to therapy with the taxane cabazitaxel. Blood was collected at baseline and after two cycles of cabazitaxel from 118 mCRPC patients starting cabazitaxel in a prospective phase II trial. CellSearch-enriched CTCs were enumerated and in parallel characterized for the presence of the AR-Vs by reverse transcription quantitative polymerase chain reaction. Correlations with CTC and prostate-specific antigen response to cabazitaxel as well as associations with overall survival (OS) were investigated. All AR-Vs were frequently present and co-expressed at frequencies of 31-48% at baseline and at 19-40% after two cycles of cabazitaxel. No specific directions of change in the measured variants were detected between the start of treatment and after two cycles of cabazitaxel. No associations between the presence of AR-V3 and AR-V7 and outcome to cabazitaxel were observed. While a reduction in CTCs to < 5 CTCs during treatment (CTC5-response) was less often observed in patients with AR-V9-positive CTCs at baseline (P = 0.004), the CTC5-adjusted detection of AR-V1 after two cycles of cabazitaxel was an independent prognostic factor for OS [HR 2.4 (95% CI 1.1-5.1, P = 0.03)]. These novel findings are expected to contribute to more personalized treatment approaches in mCRPC patients.

The Effect of Using Pazopanib With Food vs. Fasted on Pharmacokinetics, Patient Safety, and Preference (DIET Study)

Pazopanib is taken fasted in a fixed oral daily dose of 800 mg. We hypothesized that ingesting pazopanib with food may improve patients' comfort and reduce gastrointestinal (GI) adverse events. Therefore, we investigated the bioequivalent dose of pazopanib when taken with food compared with 800 mg pazopanib taken fasted. In addition, we investigated the differences in GI toxicity, patient satisfaction, and patient's preference for either intake. The intake of 600 mg pazopanib with food resulted in a bioequivalent exposure and was preferred over a standard pazopanib dose without food. No differences were seen in GI toxicities under both intake regimens. Patients seem to be more positive about their feelings about side effects and satisfaction with their therapy when pazopanib was taken with food. Forty-one of the patients (68%) preferred the intake with a continental breakfast.

Does a food intervention makes abiraterone treatment affordable?

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Background: Abiraterone is registered for metastatic prostate cancer. It is used in a fixed oral dose of 1000mg OD in a fasted state in combination with 10mg prednisone daily. Although large differences in the effect of food on abiraterone exposure are reported (ranging from 1-10 fold increase in area under the concentration time curve (AUC)) it is generally accepted that abiraterone is much better absorbed in the presence of food. By administering abiraterone with food a reduced dose can be given while maintaining equivalent abiraterone exposure. Moreover aadministering abiraterone with food is more patient friendly and it could significantly reduce the treatment costs of abiraterone.The aim of this study was to establish the bio-equivalent lower dose of abiraterone when taken with a continental breakfast compared to the standard intake of 1000mg OD in fasted state. Methods: In this phase I cross-over multi-center study abiraterone pharmacokinetics (PK) were evaluated in patients with metastatic prostate cancer who were treated with 1000 mg abiraterone in a fasted state, followed by 500 mg taken with a continental breakfast. After both periods of 14 days, abiraterone plasma exposure was measured. Bioequivalence was assumed when the GMR (fed/fasted) of the AUC0-24h and Cmax and their 90% confidence interval (CI) were within the range of 0.8 and 1.7. Results: 14 patients were enrolled into the study, of whom 12 were eligible for PK analysis. GMR (fed/fasted) AUC0-24h was 0.88 (90% CI 0.73-1.07), GMR Cmax was 1.03 (CI 0.79-1.34) and the GMR of Ctrough was 0.81 (90% CI 0.60-1.10). Conclusions: Ingesting 500mg abiraterone with a continental breakfast was not considered bio-equivalence when compared to 1000mg taken fasted. The criteria for bio-equivalence could not be met due to the large variability in pharmacokinetics of abiraterone within and between patients. Due to this large variability in abiraterone exposure, we believe that dose optimization by food intake is not a feasible strategy for abiraterone. The intake of abiraterone with food could not be advised based on the results presented in our study. Clinical trial information: NCT02883166. [Table: see text]

The impact of gastric acid suppressive agents on pazopanib exposure

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Background: Pazopanib has been registered for advanced soft tissue sarcoma (STS) and metastatic renal cell carcinoma (mRCC). The uptake of pazopanib is 40% reduced when a proton pump inhibitor is concomitantly used. Nevertheless, still a large group of cancer patients need a form of gastric acid suppressive agents (GAS, e.g. proton pump inhibitors or H2-anagonists) due to gastrointestinal adverse events. Recently, it was demonstrated that the use of pazopanib with GAS resulted in shorter overall survival and progression free survival in patients with STS. In order to limit the effect of GAS on pazopanib absorption, the advice is to take the GAS 1 hour after pazopanib. In that way the pazopanib is dosed at the lowest gastric pH value. However, the effect of this most optimal controlled intake on pazopanib absorption is unknown. Therefore, we investigated whether this controlled intake algorithm affects pazopanib exposure. Methods: In the DIET study, pazopanib trough concentrations (Ctrough) were measured at predefined moments. In this study a total of 80 patients with mRCC and STS were included. The concomitant use of GAS was recorded and taken according the intake algorithm. Patients were subdivided into two groups (with GAS or without GAS). Results: Of the 80 patients, 22 patients were treated with pazopanib in combination with GAS. In patients treated with pazopanib without GAS the geometric mean(GM) pazopanib Ctrough level was 29.1 mg/L (95% CI 26.4 -31.8) compared to 22.4 mg/L (95% CI 18.0-27.8) (p = 0.01) in those treated with GAS. Conclusions: Patient who use pazopanib with controlled intake of GAS had a 23% lower pazopanib exposure. Therefore, we advice that in patients, who are unable to quit their GAS agent, pazopanib trough concentrations should be monitored in order to prevent shorter treatment benefit. Clinical trial information: NCT02138526.

A reduced pazopanib dose with food: Is it more patient-friendly and does it reduce drug costs?

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Background: Pazopanib has been licensed for advanced soft tissue sarcoma and metastatic renal cell carcinoma in a fixed oral daily dose of 800mg taken fasted. We hypothesized that ingesting pazopanib with food may improve patients’ comfort and reduce gastro-intestinal adverse events. Moreover, a food intervention, resulting in a better absorption, can lead to a lower dose, which could significantly reduce treatment costs. Methods: Part 1 of the study was performed to determine whether 600mg pazopanib taken with a continental breakfast was bioequivalent to 800mg pazopanib taken fasted. In part 2, differences in GI-toxicity and patient satisfaction were assessed by the cancer-therapy-satisfaction-questionnaire after both intake regimens. Finally, patient’s preference for either intake regimen was asked. Results: 16 patients were included in the bioequivalence study. The geometric mean ratio (fed/fasted) of the area under the plasma concentration time curve was 1.10 (90% CI 1.00-1.19), maximum peak concentration was 1.12 (90% CI 1.02-1.22) and pazopanib trough concentration was 1.10 (90% CI 1.02-1.18). In part 2, 60 patients were included. No differences were seen in the occurrence of GI-toxicities under both intake regimens. Patients seem to be more positive about their feelings about side effects (72.3(95% CI 68.1-76.5) vs 68·2 (62.7-73.6); p=.092) and satisfaction with therapy scores were higher (84.7(95% CI 81.4-87.9) vs 81.9 (78.7-85.2); p= .059) when pazopanib was taken with food. 41 (68%) of the patients preferred the intake with continental breakfast. Conclusions: Intake of 600mg pazopanib with food results in bioequivalent exposure and was preferred over a standard pazopanib dose without food. Moreover, with this simple food intervention a large cost reduction can be realized in patients treated with pazopanib. Clinical trial information: NCT02138526.

Metronomic cyclophosphamide attenuates mTOR-mediated expansion of regulatory T cells, but does not impact clinical outcome in patients with metastatic renal cell cancer treated with everolimus

INTRODUCTION

Metastatic renal cell cancer (mRCC) patients have a median overall survival (mOS) of approximately 28 months. Until recently, mammalian target of rapamycin (mTOR) inhibition with everolimus was the standard second-line treatment regimen for mRCC patients, improving median progression-free survival (mPFS). Treatment with everolimus supports the expansion of immunosuppressive regulatory T cells (Tregs), which exert a negative effect on antitumor immune responses. In a phase 1 dose-escalation study, we have recently demonstrated that a low dose of 50 mg oral cyclophosphamide once daily can be safely combined with everolimus in mRCC patients and prevents the everolimus-induced increase in Tregs.

MATERIALS AND METHODS

In a multicenter phase 2 study, performed in patients with mRCC not amenable to or progressive on a vascular endothelial growth factor (VEGF)-receptor tyrosine kinase inhibitor (TKI) containing treatment regimen, we assessed whether the addition of this metronomic dosing schedule of cyclophosphamide to therapy with everolimus could result in an improvement of progression-free survival (PFS) after 4 months of treatment.

RESULTS

Though results from this study confirmed that combination treatment effectively lowered circulating levels of Tregs, addition of cyclophosphamide did not improve the PFS rate at 4 months. For this reason, the study was abrogated at the predefined interim analysis.

CONCLUSION

Although the comprehensive immunomonitoring analysis performed in this study provides relevant information for the design of future immunotherapeutic approaches, the addition of metronomic cyclophosphamide to mRCC patients receiving everolimus cannot be recommended.