Prediction of plasma ctDNA fraction and prognostic implications of liquid biopsy in advanced prostate cancer

No consensus strategies exist for prognosticating metastatic castration-resistant prostate cancer (mCRPC). Circulating tumor DNA fraction (ctDNA%) is increasingly reported by commercial and laboratory tests but its utility for risk stratification is unclear. Here, we intersect ctDNA%, treatment outcomes, and clinical characteristics across 738 plasma samples from 491 male mCRPC patients from two randomized multicentre phase II trials and a prospective province-wide blood biobanking program. ctDNA% correlates with serum and radiographic metrics of disease burden and is highest in patients with liver metastases. ctDNA% strongly predicts overall survival, progression-free survival, and treatment response independent of therapeutic context and outperformed established prognostic clinical factors. Recognizing that ctDNA-based biomarker genotyping is limited by low ctDNA% in some patients, we leverage the relationship between clinical prognostic factors and ctDNA% to develop a clinically-interpretable machine-learning tool that predicts whether a patient has sufficient ctDNA% for informative ctDNA genotyping (available online: https://www.ctDNA.org ). Our results affirm ctDNA% as an actionable tool for patient risk stratification and provide a practical framework for optimized biomarker testing.

Biallelic loss of TP53, PTEN, and RB1 in association to aggressive clinical features and poor outcomes in metastatic castration-resistant prostate cancer (mCRPC)

5055

Background: Deleterious alterations in tumor suppressor genes (TSGs) TP53, RB1, and PTEN are potential markers of small cell neuroendocrine prostate cancer (SCNP), and androgen receptor pathway inhibitor (ARPI) resistance. We examined the outcomes and clinical features of mCRPC patients (pts) harboring biallelic loss in 0, 1, 2 or all 3 TSGs. Methods: We identified 210 consecutive mCRPC pts providing ≥1 plasma cell-free DNA sample with ≥20% circulating tumor DNA fraction (ctDNA%) during their mCRPC disease course. ctDNA% ≥20% enabled sensitive characterization of biallelic TSG loss (including by homozygous deletions and mutation plus somatic loss-of-heterozygosity; LOH). Patient records were reviewed for baseline characteristics, SCNP histology, and presence of liver metastases. We investigated associations between TSG loss and the following clinical outcomes: PSA response (PSA decline ≥50% (PSA50 RR)), progression free survival (PFS) on 1L therapy, and overall survival (OS) from 1L therapy. Results: Median follow-up was 16.5 months (range: 0.4-112.4) and OS event rate was 95%. Median age at 1L mCRPC was 71 years (range: 48-98). Most pts were ECOG PS 0-1 (79%) and 13% had liver metastases. 91% received ARPI for 1L mCRPC and 7% received ARPI for castration-sensitive disease. TP53 was primarily inactivated by somatic mutation plus LOH (90%), whereas RB1 (71%) and PTEN (86%) were more commonly inactivated by homozygous deletions. Compared to pts without evidence of biallelic TSG loss, pts with loss of 3 TSGs were significantly enriched for de-novo M1 disease (86 vs. 60%, p=0.05) and liver metastases (28.5 vs. 6.8%, p<0.05). Ten pts (4.7%) had histologically confirmed SCNP and provided ctDNA at time of SCNP diagnosis. Of these, 7 (70%) had biallelic loss of ≥2 TSGs. For all pts receiving 1L therapy, loss of ≥1 TSG(s) was associated with decreased OS (HR: 1.86, 95% CI: 1.40-2.48, p<0.01) and PFS (HR:1.74, 95% CI 1.29-2.34, p<0.01) compared to pts with no biallelic TSG loss. Furthermore, a cumulative increase in the number of TSGs lost was associated with an incremental reduction in OS and PFS (Table). Conclusions: In a cohort enriched for poor prognosis (i.e. high ctDNA%), cumulative loss of TSGs is associated with aggressive disease features and poor clinical outcomes. These patients may benefit from alternative treatment intensification strategies. [Table: see text]

Treatment outcomes for metastatic castration-resistant prostate cancer (mCRPC) following progression on upfront androgen deprivation therapy (ADT) with androgen receptor pathway inhibitors (ARPI) for metastatic castration-sensitive prostate cancer (mCSPC)

60

Background: Combined ADT and ARPI is associated with improved overall survival (OS) compared with ADT alone in patients with mCSPC. The activity of subsequent therapies for mCRPC is not well characterized. Methods: We conducted a retrospective analysis of patients enrolled on a biobank at 6 cancer centres in British Columbia, Canada. Patients who received abiraterone or apalutamide for mCSPC were included. Data including baseline clinical prognostic factors and clinical outcomes (per Prostate Cancer Working Group III) were collected from patient records. Survival was analyzed by Kaplan-Meier method and Log Rank test and prognostic variables were determined using Cox regression. Results: 168 patients were identified of which 126 (75%) received abiraterone, 38 (23%) received apalutamide, and 4 (2%) received one ARPI and switched to the other for toxicity. Median age was 69 years and Gleason score ≥ 8 in 61%. Site of metastasis (mets) at mCSPC was lymph node (n=91), bone (n=141), and liver (n=6). As of August 28 2021, a total of 46 patients progressed to mCRPC, of which 38 received subsequent systemic therapy. First-line mCRPC treatments were docetaxel (n=12), Radium-223 (10), enzalutamide (6), platinum chemotherapy (3), and others (7) including immune checkpoint inhibitors (1) and Lutetium177-PSMA-617 (1) and other investigational agents (5). Outcomes are shown in the table. On univariate Cox analysis, clinical factors at time of mCRPC associated with worse OS were: LDH above upper limit of normal (HR 5.0, 95% CI 1.7-14.5), hemoglobin below lower limit of normal (5.2, 1.1-23.8), presence of ≥ 20 bone mets (3.7, 1.4-9.8), and increasing PSA (1.002, 1.001-1.003). Conclusions: PSA decline rates and survival are modest for patients who have progressed following upfront abiraterone or apalutamide plus ADT for mCSPC. Further follow-up is required to accurately determine outcomes with current mCRPC standard therapies following up-front ADT+ ARPI. Recently approved treatment options such as Lutetium177-PSMA-617 and PARP inhibitors for DNA damage repair deficient tumors may help to improve outcomes for these patients.[Table: see text]

Effectiveness of first-line abiraterone versus enzalutamide among patients ≥80 years of age with metastatic castration-resistant prostate cancer: A retrospective propensity score-weighted comparative cohort study

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) disproportionately affects the elderly. There is limited data assessing the efficacy and tolerability of abiraterone acetate (AA) versus enzalutamide in this population.

OBJECTIVE

To compare the clinical efficacy and tolerability of AA versus enzalutamide in patients ≥ 80 years with mCRPC.

DESIGN, SETTING AND PARTICIPANTS

A retrospective propensity-weighted comparative cohort study of first-line AA versus enzalutamide among patients with mCRPC aged ≥80 years.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Inverse probability treatment weights based on propensity scores were generated to assess the treatment effect of AA versus enzalutamide on time to PSA progression (TTPP), time to progression (TTP) (first of PSA/radiographic/clinical progression) and overall survival using a weighted Cox proportional hazards model. PSA response rate (PSA RR) was compared between groups using Χ².

RESULTS AND LIMITATIONS

One hundred fifty-three patients received AA, and 125 received enzalutamide. Enzalutamide was associated with higher PSA RR (61.6% vs 43.8%, P < 0.004), and TTP (hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.50-0.88, P = 0.01) but not TTPP (HR 0.73, 95% CI 0.53-1.01, P = 0.06). There were significantly more dose reductions with enzalutamide (22.9% vs 44.8%, P > 0.001) but there was no interaction between median proportion of full dose received and TTPP or TTP for either drug. Rates of treatment discontinuation (for reasons other than progression) were also significantly different between AA and enzalutamide (28.8% vs 40.8%, respectively, P = 0.04). The most common reason for dose reductions and discontinuation of enzalutamide was fatigue (30.4% and 5.6%, respectively).

CONCLUSIONS

Despite more dose reductions and a higher treatment discontinuation rate, enzalutamide was associated with a higher PSA RR and longer time to progression, than AA. Given that clinical outcomes were not adversely impacted by decreased treatment exposure, dose modification may be a useful treatment strategy to balance toxicity and tolerance.

Evolution of Castration-Resistant Prostate Cancer in ctDNA during Sequential Androgen Receptor Pathway Inhibition

PURPOSE

Cross-resistance renders multiple lines of androgen receptor (AR) signaling inhibitors increasingly futile in metastatic castration-resistant prostate cancer (mCRPC). We sought to determine acquired genomic contributors to cross-resistance.

EXPERIMENTAL DESIGN

We collected 458 serial plasma cell-free DNA samples at baseline and progression timepoints from 202 patients with mCRPC receiving sequential AR signaling inhibitors (abiraterone and enzalutamide) in a randomized phase II clinical trial (NCT02125357). We utilized deep targeted and whole-exome sequencing to compare baseline and posttreatment somatic genomic profiles in circulating tumor DNA (ctDNA).

RESULTS

Patient ctDNA abundance was correlated across plasma collections and independently prognostic for sequential therapy response and overall survival. Most driver alterations in established prostate cancer genes were consistently detected in ctDNA over time. However, shifts in somatic populations after treatment were identified in 53% of patients, particularly after strong treatment responses. Treatment-associated changes converged upon the AR gene, with an average 50% increase in AR copy number, changes in AR mutation frequencies, and a 2.5-fold increase in the proportion of patients carrying AR ligand binding domain truncating rearrangements.

CONCLUSIONS

Our data show that the dominant AR genotype continues to evolve during sequential lines of AR inhibition and drives acquired resistance in patients with mCRPC.

HSD3B1 (1245A>C) polymorphism and clinical outcomes in metastatic castration-resistant prostate cancer (mCRPC) patients treated with abiraterone acetate (AA) and enzalutamide (ENZA): Results from two prospective studies

5525

Background: The common HSD3B1 (1245A > C) germline variant is associated with increased de-novo synthesis of androgens and worse outcomes in men treated with androgen-deprivation therapy in metastatic hormone sensitive prostate cancer. The aim of this study is to determine the role of this polymorphism on treatment outcomes for AA and ENZA in patients with mCRPC. Methods: A total of 547 patients treated with AA or ENZA for mCRPC from two prospective cohorts; cohort 1 included 202 from British Columbia (Canada) and cohort 2 enrolled 345 patients from the Spanish study PROREPAIR-B. HSD3B1 genotype was determined by targeted sequencing in cohort 1 and by Taqman SNP genotyping assay in cohort 2. Associations between HSD3B1 genotypes and (TTPP), time to progression (TTP) and overall survival (OS) were evaluated via univariate COX regression. Multivariate analysis was performed to determine the independent association of each covariate. Results: The proportions of patients with a homozygous wild-type HSD3B1 (AA), heterozygous (AC) and homozygous variant (CC) genotype were respectively 45.6%, 39.4% and 15%. As expected, known prognostic factors for mCRPC such as hemoglobin, alkaline phosphatase (ALP), LDH, PSA at baseline as well as site of metastasis were significantly associated with TTPP and TPP. In the combined cohort, HSD3B1 (CC) genotype was associated with worse TTP (HR 1.31, 95%CI 1.02-1.67, p = 0.032) and PSA response rates (48% for CC vs 62% and 65% for AA and AC, respectively (p = 0.019, χ²)). Similar trend was observed for TTPP (HR 1.28, 95%CI 0.99-1.66, p = 0.064). OS was not different among genotypes, but was significantly shorter for patients with CC genotype in cohort 1 (HR 1.97, 95%CI 1.14-3.40, p = 0.016). There was no association between HSD3B1 genotype and time to castration-resistance in either of the two cohorts. Multivariable analysis showed that LDH, ALP, hemoglobin and use of AA or ENZA as first-line therapy for mCRPC were independent prognostic factors for TTP and TTPP; non-significant association was observed for genotype and TTP. Conclusions: HSD3B1 homozygous variant genotype (CC) was associated with shorter TTP and lower PSA response rate in mCRPC patients treated with AA or ENZA. However, the CC genotype did not provide prognostic information beyond that conferred by standard clinical variables, suggesting that it may not be a suitable stand-alone biomarker in mCRPC.

Quality of life (QOL) for the treatment sequence of abiraterone acetate plus prednisone (AAP) followed by enzalutamide (ENZ) versus the opposite sequence for metastatic castration-resistant prostate cancer (mCRPC): Results from a phase II randomized clinical trial

5578

Background: A randomized cross-over phase II trial (Lancet Oncol 20(12):1730, 2019) showed the sequence of AAP followed by ENZ is associated with a better time to PSA progression compared with the opposite sequence and superior 2nd line activity of ENZ. It is unknown whether one treatment sequence is associated with better QOL than the other. Methods: 202 Patients were randomized (1:1) to receive either AAP followed by ENZ at PSA progression (arm A) or the opposite sequence of ENZ followed by AAP (arm B). FACT-P questionnaires were completed at baseline, cross-over and every 4 weeks on treatment. Time to QOL deterioration (TTQOLD) for the treatment sequence was determined from start of 1st line treatment to first questionnaire with a clinically meaningful decrease from baseline and compared between arms using the log-rank test. TTQOLD was also determined for 1st line and 2nd line separately. The proportion of patients with QOL deterioration for total FACT-P score and FACT-P subscores from baseline to week 12 of 1st and 2nd line treatment was compared between arms using X2 test. Results: Median follow-up for 1st and 2nd line and whole sequence were 9.3, 6.6 and 22.0 months (mos) respectively and questionnaire completion rate was 81%. TTQOLD for total FACT-P score for the whole sequence for arm A vs B was 10.5 mo (95% CI 5.0-15.5) vs 10.8 mo (5.5-13.1), p = 0.74. For 1st-line AAP vs ENZ, median TTQOLD was 15.5 mo (5.5-21.2) vs 11.0 (5.5-13.3) respectively (p = 0.23). For 2nd line ENZ vs ABI, median TTQOLD was 3.7 mo (2.0-5.4) vs 5.8 (2.8-12.1), p = 0.13. There was a higher rate of deterioration in physical well-being (PWB) for 1st line ENZ (arm B) and 2nd line ENZ (arm A) (Table). Conclusions: There was no difference in TTQOLD between the two treatment sequences of AAP and ENZ. Although treatment with second line ENZ has been associated with greater anti-cancer effects, ENZ was associated worse PWB QOL scores. Clinical trial information: NCT02125357 . [Table: see text]

Clinical effectiveness of docetaxel for castration-sensitive prostate cancer in a real-world population-based analysis

BACKGROUND

Adding docetaxel to androgen deprivation therapy (ADT) for the treatment of metastatic castration-sensitive prostate cancer (mCSPC) has known efficacy, with an overall survival benefit in Phase III clinical trials. The effectiveness of docetaxel with ADT in the general patient population remains undefined.

PATIENTS AND METHODS

We conducted a population-based retrospective review using the British Columbia Provincial Pharmacy Database. To be included, patients had to have castration-sensitive prostate cancer not previously treated (except in the adjuvant setting) and have received at least one cycle of docetaxel, with complete records available for review. Safety and clinical effectiveness were evaluated.

RESULTS

From April 2015 to February 2017, we identified 183 cases; 156 met inclusion criteria. Most patients had high-volume disease (80%). All 6 planned docetaxel cycles were delivered in 126 cases (81%). Dose reductions and delays were required in 39% and 16% of cases. Grade 3-4 adverse events were noted in 40%, with no treatment-related deaths. The rate of febrile neutropenia was 18% and was significantly associated with the presence of high-volume disease (P = 0.038). PSA ≤ 0.2 ng/L was achieved in 27% of patients after 6 months of ADT and maintained in 16% after 12 months. Patients with over 20 bone metastases had worse time to castration resistant prostate cancer (CRPC) and time to treatment for CRPC, and a trend toward worse overall survival. CRPC developed in 41% within 1 year, with a median time to CRPC of 14.4 months. Treatment for CRPC was given in 84 cases, with 90% receiving either abiraterone or enzalutamide in the first-line, with a PSA decline ≥50% occurring in 47%.

CONCLUSIONS

The effectiveness of docetaxel with ADT in a general population of patients with mCSPC was associated with poorer outcomes and high rates of toxicity compared to the published studies. Response rates to first-line treatment for mCRPC with abiraterone or enzalutamide appear similar to reported outcomes.

Real-world experience with docetaxel for castration-sensitive prostate cancer from a population-based analysis

297

Background: Phase III clinical trials have demonstrated efficacy with an overall survival (OS) benefit for the addition of docetaxel (DOC) to androgen deprivation therapy (ADT) for the treatment of metastatic castration-sensitive prostate cancer (mCSPC). The clinical effectiveness of DOC with ADT in the general patient population remains undefined. Methods: A population-based retrospective review was conducted of patients (pts) with mCSPC who received DOC at the BC Cancer Agency from 04/2015 to 02/2017. Patient and disease characteristics were extracted. Safety and clinical-effectiveness were evaluated. Results: 183 records were identified; 156 pts received DOC in the mCSPC setting. Baseline characteristics included a median age of 67 years (range 44-86) and visceral metastases (mets) present in 18%; 80% had high volume disease with 74% having > 3, and 54% > 10 bone mets; 76% had de-novo metastatic disease. All 6 planned DOC cycles were delivered in 126 cases (81%); it was stopped early for: toxicity in 15 (10%), unrelated death in 1 (0.6%), pt preference in 5 (3%) or disease progression in 9 (6%) cases. Dose reductions and delays were required in 61 (39%) and 25 (16%) cases, respectively. Grade 3-5 adverse events were noted in 62 (40%) cases, with 28 (18%) cases of febrile neutropenia (FN); there were no treatment-related deaths. Pts with FN had more bone mets (p = 0.046), but there was no difference in time from start of ADT to initiation of docetaxel, age, baseline performance status, PSA, or visceral involvement. PSA ≤ 0.2 ng/L was achieved in 41 (28%) cases after 6 months of ADT and maintained in 13 (8%) cases after 12 months. 41% of pts had developed CRPC within 1-yr, with a median time to CRPC of 14.3 months. Treatment for CRPC was given in 54 cases, with most pts receiving either abiraterone or enzalutamide (87%) with a PSA decline ≥50% occurring in 47%. Conclusions: Effectiveness of DOC with ADT in a general population of pts with mCSPC was associated with poorer outcomes and high rates of toxicity compared to the phase III studies. Response rates to first-line treatment for mCRPC with abiraterone or enzalutamide appear similar to those previously reported.

Determining biomarkers of response to docetaxel for patients with metastatic castration-resistant prostate cancer (mCRPC) using circulating cell-free tumor DNA (ctDNA)

260

Background: Docetaxel is associated with improved outcomes for mCRPC. There are currently no predictive molecular biomarkers for docetaxel to assist with patient selection. Methods: Patients commencing docetaxel for mCRPC between November 2015 and August 2017 were enrolled on a prospective cohort study evaluating circulating biomarkers. A plasma sample for ctDNA analysis was collected before initiation of docetaxel. Targeted sequencing of 73 prostate cancer-relevant genes was performed on leukocyte DNA (germline) and plasma cell-free DNA. Patient records were reviewed for baseline clinical characteristics, PSA response (≥ 50% decline from baseline), and time to PSA progression (TTPP) (PCWG3 criteria). Results: There were 33 patients enrolled; all patients had received prior abiraterone or enzalutamide and none had received prior taxanes. At baseline, the median age was 69.9 years, 30.3% had ECOG performance status 2, 66.7% had bone metastasis and 9.1% had liver metastases. The PSA response rate (RR) was 39.4% and 33.3% had a TTPP less than 3 months. 82% of patients had a ctDNA fraction >5%. Deleterious BRCA2 or ATM defects were present in 12.1% (4/33) of patients (3 somatic and 1 germline). TP53 alterations were identified in 39.4% (13/33), RB1 loss in 21.2% (7/33), PTEN loss in 21.2% (7/33), and Androgen Receptor (AR) amplification in 42.2% (14/33). PTEN deletion was associated with a trend toward inferior RR and TP53 had no discernible effect on PSA RR (Table). BRCA2/ATM defects were associated with a trend toward a lower rate of PSA progression within 3 months (Table). Conclusions: In this preliminary analysis, TP53 alterations had no discernible effect on efficacy of docetaxel chemotherapy. Accrual is ongoing in order to further clarify whether there is an association between PTEN, RB1, AR and BRCA2/ATM alterations and benefit from docetaxel. [Table: see text]

Circulating Tumor DNA Genomics Correlate with Resistance to Abiraterone and Enzalutamide in Prostate Cancer

Primary resistance to androgen receptor (AR)-directed therapies in metastatic castration-resistant prostate cancer (mCRPC) is poorly understood. We randomized 202 patients with treatment-naïve mCRPC to abiraterone or enzalutamide and performed whole-exome and deep targeted 72-gene sequencing of plasma cell-free DNA prior to therapy. For these agents, which have never been directly compared, time to progression was similar. Defects in BRCA2 and ATM were strongly associated with poor clinical outcomes independently of clinical prognostic factors and circulating tumor DNA abundance. Somatic alterations in TP53, previously linked to reduced tumor dependency on AR signaling, were also independently associated with rapid resistance. Although detection of AR amplifications did not outperform standard prognostic biomarkers, AR gene structural rearrangements truncating the ligand binding domain were identified in several patients with primary resistance. These findings establish genomic drivers of resistance to first-line AR-directed therapy in mCRPC and identify potential minimally invasive biomarkers.Significance: Leveraging plasma specimens collected in a large randomized phase II trial, we report the relative impact of common circulating tumor DNA alterations on patient response to the most widely used therapies for advanced prostate cancer. Our findings suggest that liquid biopsy analysis can guide the use of AR-targeted therapy in general practice. Cancer Discov; 8(4); 444-57. ©2018 AACR.See related commentary by Jayaram et al., p. 392This article is highlighted in the In This Issue feature, p. 371.

A randomized phase II cross-over study of abiraterone + prednisone (ABI) vs enzalutamide (ENZ) for patients (pts) with metastatic, castration-resistant prostate cancer (mCRPC)

5002

Background: ABI and ENZ are indicated as 1st line therapy for mCRPC but have not been directly compared. Optimal sequencing of these agents has not been prospectively evaluated and predictive biomarkers are lacking. Methods: Multicenter, phase 2 study randomizing treatment-naïve mCRPC pts to ABI vs ENZ, with cross over at PSA progression. Primary endpoints: response and time to PSA progression (TTPP, PCWG3 criteria) after 2nd line therapy. Reported here are secondary endpoints: PSA ≥50% decline (PSA50) from baseline, TTPP with 1stline therapy, and correlation with deep targeted sequencing of 73 mCRPC genes in circulating tumor DNA (ctDNA). Results: Accrual completed October 2016 with 202 pts randomized (ABI:ENZ = 101:101). Median follow-up 12.8 months. Baseline characteristics were similar between arms: median for age was 75 years (range 49-94), PSA 36.1 (1.7-2817), HGB 130 (89-165), ALK PHOS 105 (31-6600), LDH 207 (77-3098). ECOG PS was 0-1 in 83%, presence of metastases in bone/liver/lung in 83%/6%/10%. With 1stline therapy for ABI vs ENZ, PSA50 at 12 weeks was 53% vs 73% (P = 0.004), no PSA decline occurred in 21% vs 15% (P = 0.243), and median TTPP was 7.4 vs 8.0 months (HR = 0.88, 95% CI 0.61, 1.27). Baseline ctDNA fraction was >2% in 60% of patients, and associated with worse TTPP (HR 1.80, P=0.005). Baseline pathogenic ctDNA alterations in AR, TP53, RB1, and DNA repair (BRCA2, ATM) genes were associated with a shorter TTPP (univariate analysis: TABLE). On multivariate analysis including clinical factors, TP53 and BRCA2/ATM alterations remained significant (HR = 2.54 (95%CI 1.55-4.19) and HR = 2.68 (1.58-4.54)). Pts with a PSA increase as best response were enriched for alterations in DNA repair (P <0.001), TP53 (P = 0.005), RB1 (P = 0.04), and (in 1 pt) a genomically truncated AR. Conclusions: There was a difference in PSA response for 1stline ABI vs ENZ, but no difference for TTPP. Baseline pathogenic ctDNA alterations, particularly in TP53 and BRCA2, identify pts with poor outcomes. Clinical trial information: NCT02125357. [Table: see text]

Assessment of quality of life (QOL), cognitive function and depression in a randomized phase II study of abiraterone acetate (ABI) plus prednisone (P) vs enzalutamide (ENZA) for metastatic castrate-resistant prostate cancer (mCRPC)

5036

Background: ABI + P and ENZA treatments are associated with side effects that may impair QOL. ENZA has been associated with cognitive and memory impairment. There has been no direct comparison between these agents and their effect on these domains. Methods: Randomized phase II trial of ABI + P vs ENZA as 1st-line therapy for mCRPC (ClinicalTrials.gov: NCT02125357). FACT-P QOL questionnaire, patient health questionnaire (PHQ-9) and Montreal Cognitive Assessment (MoCA) were completed throughout the study. The proportion of patients with a clinically significant change in FACT-P (10 points total FACT-P score, 3 points FACT-P subscales), worsening of PHQ-9 depression symptom severity (none = 0-4, mild = 5-9, moderate = 10-14, moderate-severe = 15-19, severe ≥20) and decline in MoCA cognitive impairment level (normal = 27-30, mild = 18-26, moderate = 10-17, severe ˂ 10) at week 12 was compared between study arms for this analysis. Results: From 202 patients (pts) accrued, there were 162, 145 and 142 pts with baseline and 12-week FACT-P, PHQ-9 and MoCA assessment. Median baseline FACT-P, PHQ-9 and MoCA scores were similar in both arms. From baseline to 12 weeks, the median total FACT-P score improved in the ABI + P arm (115 to 128, P = 0.02), but there was no change in the ENZA arm (114 to 114, P = 1.00). There was a higher rate of significant worsening for the physical well-being (PWB) subscale for ENZA vs ABI + P (TABLE), but not for the other FACT-P subscales. There was a higher rate of worsening in depression severity in the ENZA arm (TABLE), although worsening to a moderate-severe/severe level occurred in only 2 patients. There was also a trend for worsening in cognitive impairment for the ENZA arm (TABLE). Conclusions: These data suggest there are distinct differences between ABI + P vs ENZA and their effects on QOL, mood symptoms and cognitive function. Clinical trial information: NCT02125357. [Table: see text]

Circulating tumor DNA (ctDNA) and correlations with clinical prognostic factors in patients with metastatic castration-resistant prostate cancer (mCRPC)

186

Background: Sequencing of ctDNA is a minimally invasive method to study somatic DNA alterations. Quantitation and characterization of ctDNA may correlate with tumor burden and poor risk clinical features, but this is unproven in mCRPC. Methods: We performed deep targeted sequencing of 73 mCRPC-related genes in plasma ctDNA from 136 treatment naïve mCRPC patients. Fraction of ctDNA was determined by quantifying somatic mutant allele frequency and the deviation from heterozygosity for germline single nucleotide polymorphisms at regions of somatic copy number alterations. Baseline clinical factors were correlated with ctDNA fraction and genomic aberrations. Results: ctDNA could be quantified in 86/136 (63%) patients. Increasing fraction correlated with elevated ALP (chi2, p < 0.001), LDH (p < 0.001) and presence of liver metastasis (p = 0.01). Patients with any one of these factors were more likely to have a ctDNA fraction ≥ 40% (67% vs 36% of patients with neither factor, p = 0.001) and less likely to have unquantifiable ctDNA (26% vs 49%, p = 0.006). A decreased ctDNA fraction was associated with metastases only to lymph nodes (p = 0.012). Among the most frequently aberrant genes were Androgen Receptor (AR), p53, RB1, and PTEN, present in 38%, 30%, 23% and 22% of patients, respectively. Aberrations were associated with poor prognosis factors, including: AR and p53 alterations, which both correlated with presence of liver metastasis (p = 0.020 and p = 0.004 respectively), elevated LDH (p = 0.001, p < 0.001), and presence of ≥ 10 bone metastasis (p = 0.018, p = 0.017); PTEN deletion which correlated with elevated ALP (p < 0.001), elevated LDH (p = 0.001), ≥ 10 bone metastasis (p = 0.009) and time to CPRC of < 12 months (p = 0.021); and RB1 correlated with ≥ 10 bone metastasis (p = 0.009). Conclusions: We found an association between poor prognostic factors and increasing ctDNA fraction in patients with mCRPC. Genomic aberrations, particularly alteration in AR, p53 and PTEN, correlated with poor prognostic factors. These data show that clinical factors may help predict ctDNA yield in patients with mCRPC, and also provide insight into the role of deleterious genetic alterations.

Immune Modulation by Androgen Deprivation and Radiation Therapy: Implications for Prostate Cancer Immunotherapy

Prostate cancer patients often receive androgen deprivation therapy (ADT) in combination with radiation therapy (RT). Recent evidence suggests that both ADT and RT have immune modulatory properties. First, ADT can cause infiltration of lymphocytes into the prostate, although it remains unclear whether the influx of lymphocytes is beneficial, particularly with the advent of new classes of androgen blockers. Second, in rare cases, radiation can elicit immune responses that mediate regression of metastatic lesions lying outside the field of radiation, a phenomenon known as the abscopal response. In light of these findings, there is emerging interest in exploiting any potential synergy between ADT, RT, and immunotherapy. Here, we provide a comprehensive review of the rationale behind combining immunotherapy with ADT and RT for the treatment of prostate cancer, including an examination of the current clinical trials that employ this combination. The reported outcomes of several trials demonstrate the promise of this combination strategy; however, further scrutiny is needed to elucidate how these standard therapies interact with immune modulators. In addition, we discuss the importance of synchronizing immune modulation relative to ADT and RT, and provide insight into elements that may impact the ability to achieve maximum synergy between these treatments.

Impact of Weight Changes After the Diagnosis of Stage III Colon Cancer on Survival Outcomes

BACKGROUND

Weight modification after a diagnosis of colon cancer and its impact on outcomes remain unclear. Thus we aimed to examine the association of obesity and weight changes from baseline oncology consultation with recurrence-free survival (RFS) and overall survival (OS) in patients with stage III colon cancer.

METHODS

Patients aged ≥ 18 years who were diagnosed with stage III colon cancer in British Columbia from 2008 to 2010 and who received adjuvant chemotherapy were included in the study. Cox proportional hazards regression models were fitted to evaluate the impact of different body compositions and degree of weight changes from baseline assessment with outcomes while controlling for potentially confounding covariates, such as age and sex.

RESULTS

A total of 539 patients with stage III colon cancer were included: median age was 69 years (range, 26-94 years), 52% were men, and 53% had Eastern Cooperative Oncology Group (ECOG) performance status of 0-1. Those with weight gains of ≥ 10% had a median RFS of 37 months compared with 49 months in those with weight gains of < 10% (hazard ratio [HR], 0.94; 95% confidence interval [CI], 0.56-1.59; P = .82). However, this finding was not significant. In Cox models, patients who exhibited weight losses of ≥ 10% experienced significantly inferior RFS (HR, 3.45; 95% CI, 1.44-8.13; P = .0046) and OS (HR, 2.63; 95% CI, 1.04-6.67; P = .041) compared with those who experienced weight losses of < 10%. Weight gains, losses, or changes of equal or less magnitude did not show any significant associations with outcomes (all P > .05).

CONCLUSIONS

Weight losses of ≥ 10% from baseline evaluation bodes a worse prognosis among patients with stage III colon cancer.

Cost-effectiveness of therapies for melanoma

Melanoma presents an important burden worldwide. Until recently, the prognosis for unresectable and metastatic melanoma was poor, with 10% of metastatic melanoma patients surviving for 2 years. The introduction of newer therapies including ipilimumab, vemurafenib, dabrafenib and trametinib improved progression-free survival, with additional benefits anticipated from the forthcoming class of programmed cell death 1 inhibitors. Cost of therapy and resulting cost-effectiveness is an important factor in determining patient access to specific treatments. The objective of this study was to review the published evidence regarding cost-effectiveness of melanoma therapies and provide an overview of the relative cost-effectiveness of available therapies by disease stage. For earlier-stage disease, IFN-α has been found to be cost-effective, although its clinical benefits have not been well established. For unresectable and metastatic melanoma, newer therapies provide benefits over standard-of-care chemotherapy, but comprehensive analyses will need to be conducted to determine the most cost-effective therapy.

Outcome and prognostic factors in BRAF mutation positive metastatic melanoma treated with a BRAF inhibitor: A population-based study in British Columbia

e20045

Background: BRAF mutations are present in approximately 40-60% of cutaneous melanomas. The BRAF inhibitor vemurafenib has demonstrated dramatic anti-tumour activity in phase III trials in BRAF mutation positive (BRAFm) metastatic/unresectable melanoma; however, there is limited data outside of clinical trials. Methods: All patients > 18 years of age, PS 0-2, with metastatic/unresectable melanoma considered for treatment with vemurafenib in British Columbia between March 2011 to December 2012 were identified. CNS disease, if present, had to be radiographically stable/asymptomatic and treated with radiation and/or surgery. The BRAF V600E mutation status was evaluated centrally on primary or metastatic biopsies using a real-time PCR assay (Cobas 4800 BRAF Mutation Test, Roche Molecular Systems). Vemurafenib was initially provided through an Expanded Access Program/Roche patient assistance program and subsequently through provincial funding. Results: In total, 84 patients were identified that had undergone BRAF mutation screening, 49(58%) were BRAFm, 35(42%) were BRAFwt. For the BRAFm patients 33 have received 1 cycle of vemurafenib and are included in the present analysis (n=21 (64%) 1st line therapy; 12(36%) > 1st line therapy). BRAFm patients: median age 53 y; 64% male; PS 0/1 76%; LDH elevated 51.5%; M1c 91%; 27% history CNS metastases. With a median follow-up of 4.9 m the median PFS, measured from the 1st dose of vemurafenib, was 9 m and the median OS was 12.4 m. The 1 year PFS and OS were 47% and 50%, respectively. The median OS of patients who progressed following vemurafenib was only 2 months. There was an inferior PFS in patients with an elevated LDH (median PFS 5 m vs not reached, p=0.024) prior to receiving vemurafenib. Conclusions: The efficacy of vemurafenibin BRAF + melanoma in this population-based analysis compares favorably to estimates in the clinical trial setting. The survival of patients who progress on vemurafenib is short, highlighting the need to explore combination therapies. An updated analysis will be presented.

Impact of body mass index (BMI) and weight changes on recurrence and survival in stage III colon cancer (CC)

355

Background: Research suggests that physical activity can lower the risk of relapse and mortality from CC. However, it is unclear if such benefits are mediated through an effect on weight. Our aims were to (1) evaluate the impact of pre-treatment BMI on recurrence and survival in early stage CC, (2) examine how changes in weight from baseline may affect outcomes, and (3) explore if the effects of different body compositions are modified by adjuvant therapy (AT). Methods: Patients (pts) diagnosed with stage III CC from 2006 to 2008, evaluated at any 1 of 5 cancer centers in British Columbia, and who had their weights measured serially throughout their AT period were reviewed. Using Cox proportional hazards models, we compared outcomes among (a) BMI<25 [normal] vs. 25-30 [overweight] vs. >30 [obese] and (b) weight increase or decrease of < vs. >/=5% and < vs. >/=10%, while controlling for confounders. Results: A total of 821 pts were included: median age was 65 years, 50% were men, and 83% were ECOG 0/1. At baseline, 43, 37, and 20% were normal, overweight, and obese, respectively. Compared to pts with normal BMI, those who were overweight or obese did not show an increased risk of recurrence (HR 0.81, 95%CI 0.42-1.58 and HR 1.09, 95%CI 0.48-2.51, respectively, p trend=0.74) or death (HR 0.54, 95%CI 0.26-1.13 and HR 0.62, 95%CI 0.22-1.74, respectively, p trend=0.24). A number of pts experienced weight gain or loss during their AT period, but none of these weight changes affected outcomes (Table). Receipt of AT did not modify the effects of BMI or weight change on outcomes. In Cox models, advanced age and poor performance status were the main factors that consistently correlated with an increased risk of recurrence and death (p<0.05). Conclusions: Neither baseline BMI nor short-term weight changes during AT appear to affect outcomes in stage III CC. Physical activity likely exerts its benefit on relapse and survival by influencing long-term weight changes or by alternative mechanisms. [Table: see text]

Impact of body mass index (BMI) and weight changes on recurrence and survival in stage III colon cancer (CC)

3560

Background: Research suggests that physical activity can lower the risk of relapse and mortality from CC. It is unclear if such potential benefits are mediated through an effect on weight. Our aims were to 1) evaluate the impact of pre-treatment BMI on recurrence and survival in early stage CC, 2) examine how weight gains and losses from baseline may affect outcomes, and 3) explore if the effects of different body compositions are modified by adjuvant therapy (AT). Methods: Patients (pts) diagnosed with stage III CC from 2006 to 2008, evaluated at any 1 of 5 cancer centers in British Columbia, and who had their weights measured serially throughout their AT period were reviewed. Using Cox proportional hazards models, we compared outcomes among a) BMI<25 [normal] vs. 25-30 [overweight] vs. >30 [obese] and b) weight increase or decrease of < vs. >/=5% and < vs. >/=10%, while controlling for confounders. Results: A total of 821 pts were included: median age was 65 years, 50% were men, and 83% were ECOG 0/1. At baseline, 43, 37, and 20% were normal, overweight, and obese, respectively. Compared to pts with normal BMI, those who were overweight or obese did not show an increased risk of recurrence (HR 0.81, 95%CI 0.42-1.58 and HR 1.09, 95%CI 0.48-2.51, respectively, p trend=0.74) or death (HR 0.54, 95%CI 0.26-1.13 and HR 0.62, 95%CI 0.22-1.74, respectively, p trend=0.24). A number of pts experienced weight gain or loss during their AT period, but none of these weight changes affected outcomes (Table). Receipt of AT did not modify the effects of BMI or weight change. In Cox models, advanced age and poor performance status were the main factors that consistently correlated with an increased risk of recurrence and death (p<0.05). Conclusions: Neither baseline BMI nor short-term weight changes during AT appear to affect outcomes in stage III CC. Physical activity likely exert its benefit on relapse and survival by influencing long-term weight changes or acting via other alternative mechanisms. [Table: see text]

KHYG-1, a model for the study of enhanced natural killer cell cytotoxicity

OBJECTIVE

To compare the cytotoxicity of KHYG-1 with other natural killer (NK)/NK T-cell lines and identify molecules that may be associated with enhanced cytotoxicity, thereby eventually leading to improved NK cell-mediated cancer immunotherapy.

MATERIALS AND METHODS

NK/NK T-cell lines KHYG-1, NK-92, YT, and SNT-8 were compared with a novel flow cytometric cytotoxicity assay under different culture conditions. Transcription, expression, and phosphorylation studies were performed using polymerase chain reaction sequence-specific primers, reverse transcription polymerase chain reaction, immunoblotting, and flow cytometry.

RESULTS

KHYG-1 is a highly cytotoxic cell line, exceeding the cytolytic capacity of the other cell lines against K562. KHYG-1 is also highly cytotoxic against the leukemia cell lines EM2, EM3, and HL60. The novel activation receptor NKp44 and its adaptor, DAP12, NKG2D, and constitutively phosphorylated ERK2 may be associated with the enhanced cytotoxicity of KHYG-1. This cell line most likely mediates cytolysis by granzyme M (but not granzymes A and B) together with perforin, which is constitutively fully cleaved to the 60-kD form, in contrast to the other cell lines.

CONCLUSION

KHYG-1 is a valuable model for the study of enhanced cytotoxicity by NK cells. In addition to the activation of NKp44, KHYG-1 may induce apoptosis of tumor cells by the newly described granzyme M/perforin pathway. Targeted modifications of effector molecules demonstrated in this model could generate NK cells with even greater killing ability that may be particularly attractive for clinical application. Moreover, our demonstration of greater cytotoxicity of KHYG-1 versus NK-92 cells, already in clinical trials, suggests a direct therapeutic role for KHYG-1.