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.

Genetic testing practices among specialist physicians who treat prostate cancer A Canadian, cross-sectional survey.

INTRODUCTION: In patients with prostate cancer (PCa), the identification of an alteration in genes associated with homologous recombination repair (HRR) has implications for prognostication, optimization of therapy, and familial risk mitigation. The aim of this study was to assess the genomic testing landscape of PCa in Canada and to recommend an approach to offering germline and tumor testing for HRR-associated genes. METHODS: The Canadian Genitourinary Research Consortium (GURC) administered a cross-sectional survey to a largely academic, multidisciplinary group of investigators across 22 GURC sites between January and June 2022. RESULTS: Thirty-eight investigators from all 22 sites responded to the survey. Germline genetic testing was initiated by 34%, while 45% required a referral to a genetic specialist. Most investigators (82%) reported that both germline and tumor testing were needed, with 92% currently offering germline and 72% offering tissue testing to patients with advanced PCa. The most cited reasons for not offering testing were an access gap (50%), uncertainties around who to test and which genes to test, (33%) and interpreting results (17%). A majority reported that patients with advanced PCa (74-80%) should be tested, with few investigators testing patients with localized disease except when there is a family history of PCa (45-55%). CONCLUSIONS: Canadian physicians with academic subspecialist backgrounds in genitourinary malignancies recognize the benefits of both germline and somatic testing in PCa; however, there are challenges in accessing testing across practices and specialties. An algorithm to reduce uncertainty for providers when ordering genetic testing for patients with PCa is proposed.

Real-world experience managing unresectable or metastatic small cell carcinoma of the prostate.

INTRODUCTION: Unresectable and metastatic small cell carcinoma of the prostate (SCPC) is a rare and aggressive disease that is under-represented in clinical trials. We carried out a retrospective chart review of metastatic or unresectable SCPC patients at British Columbia (BC) Cancer centers, studying diagnosis and treatment patterns. METHODS: Drug-dispensing records from the six BC Cancer centers were obtained from 2002-2017. For each patient, information was collected on baseline information prior to therapy and for each line of treatment. Treatments at each line were compared regarding time to progression and overall survival by Kaplan-Meier curves. RESULTS: Forty-one patients received treatment; 65.6% had metastatic disease and 61% had pure small cell carcinoma. Median time from treatment to death was 10 months (95% confidence interval [CI] 6-16). Patients with initially prostate-confined disease had a better median overall survival (mOS) of 21 months (95% CI 13-34) compared to those with initially locally advanced (mOS 19 months, 95% CI 5-37) and metastatic disease (mOS 8 months, 95% CI 6-10) (log-rank p=0.0364). All patients received either cisplatin- or carboplatin-based combination chemotherapy as the first-line treatment and 36.7% received second-line therapy. Time to second-line therapy was eight months for those who presented with metastatic SCPC, compared to 13 months for those with initial non-metastatic SCPC. CONCLUSIONS: This single-province, multi-institution cohort reports data on unresectable and metastatic SCPC and highlights the poor prognosis of this rare disease entity.

Pain response in a population-based study of radium-223 (Ra223) for metastatic castration-resistant prostate cancer.

INTRODUCTION: Clinical trials have shown that radium-223 (Ra223) can prolong survival and improve quality of life in patients with metastatic castration-resistant prostate cancer (mCRPC). The objectives of this study were to evaluate pain responses with Ra223 at a population-based level and to determine if there is an association between pain response and alkaline phosphatase (ALP) response. METHODS: All patients from the Vancouver and Kelowna Cancer Centers (CC) in British Columbia who were treated with Ra223 between June 2015 and December 2016 were identified. Patients completed the Brief Pain Inventory (BPI) just prior to each Ra223 injection. Pain response was defined as a two or more point improvement in worst pain relative to baseline, without an increase in pain medication level. ALP was determined at each visit, with a response threshold defined as a 30% decrease from baseline, consistent with the definition of response used in the ALSYMPCA trial. RESULTS: A total of 65 patients in Vancouver and Kelowna CC received Ra223 during the study period and 56 patients had at least one BPI record, of which 44 (79%) patients were assessable for change in worst pain. Of the assessable patients, 23 (52%, 95% confidence interval [CI] 38-67) had a pain response, although the use of concurrent external beam radiotherapy was a confounder in four cases. Of the 44 patients assessable for change in worst pain, 59% had ALP responses greater than 30%. An ALP response was seen in 56% of pain-responders vs. 43% of non-pain-responders. There was no association between pain response and ALP response (Phi =-0.05; p=0.77). CONCLUSIONS: Ra223 administration was associated with a meaningful pain response rate in this cohort. There was no correlation between pain response and ALP response.

Biallelic tumour suppressor loss and DNA repair defects in de novo small-cell prostate carcinoma.

Small-cell prostate carcinoma (SCPC) is an aggressive malignancy that is managed similarly to small-cell lung cancer. SCPC can evolve from prostate adenocarcinoma in response to androgen deprivation therapy, but, in rare cases, is present at initial cancer diagnosis. The molecular aetiology of de novo SCPC is incompletely understood, owing to the scarcity of tumour tissue and the short life-expectancy of patients. Through a retrospective search of our regional oncology pharmacy database, we identified 18 patients diagnosed with de novo SCPC between 2004 and 2017. Ten patients had pure SCPC pathology, and the remainder had some admixed adenocarcinoma foci, but all were treated with first-line platinum-based chemotherapy. The median overall survival was 28 months. We performed targeted DNA sequencing, whole exome sequencing and mRNA profiling on formalin-fixed paraffin-embedded archival tumour tissue. We observed frequent biallelic deletion and/or mutation of the tumour suppressor genes TP53, RB1, and PTEN, similarly to what was found in treatment-related SCPC. Indeed, at the RNA level, pure de novo SCPC closely resembled treatment-related SCPC. However, five patients had biallelic loss of DNA repair genes, including BRCA1, BRCA2, ATM, and MSH2/6, potentially underlying the high genomic instability of this rare disease variant. Two patients with pure de novo SCPC harboured ETS gene rearrangements involving androgen-driven promoters, consistent with the evolution of de novo SCPC from an androgen-driven ancestor. Overall, our results reveal a highly aggressive molecular landscape that underlies this unusual pathological variant, and suggest opportunities for targeted therapy strategies in a disease with few treatment options. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Evolution of Metastatic Colorectal Cancer Clinical Trials: Application of the ASCO Framework for Assessing Value.

Background: Phase III trials in metastatic colorectal cancer (mCRC) have collectively led to progressive advancements in patient outcomes over the past decades. This study characterizes the evolution of mCRC phase III trials through assessing the value of cancer therapy, as measured by the ASCO Value Framework. Methods: Phase III trial results of systemic therapy for mCRC published between 1980 and 2015 were identified, and their outcome, statistical significance, journal impact factor, and citation by the 2016 NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for CRC were recorded. For each trial, the net health benefit (NHB) score was calculated using the June 2015 (original) and May 2016 (revised) ASCO Value Framework: Advanced Disease. Results: There were 114 mCRC phase III trials eligible for calculation of the NHB score. Using the revised framework, the median NHB score was 4.6 (range, -30 to 43.5); 12% of trials received bonus points. Trials with statistically significant results had higher NHB scores compared with nonsignificant trials (median NHB score, 21.6 vs 2.9; P<.0001). Clinical trials cited in the NCCN Guidelines had higher NHB scores than those not cited (median score, 8.0 vs 0.3; P=.02). In multivariate linear regression analysis, the only significant predictor of high NHB score was statistically significant studies. Conclusions: The median NHB score for mCRC phase III trials was 4.6. Higher NHB scores are associated with statistically significant studies and are cited in the NCCN Guidelines, a surrogate for practice-changing trials. The 2016 ASCO Value Framework may not fully capture the benefits on an individual patient level.

Drug development for breast, colorectal, and non-small cell lung cancers from 1979 to 2014.

BACKGROUND: Understanding the drug development pathway is critical for streamlining the development of effective cancer treatments. The objective of the current study was to delineate the drug development timeline and attrition rate of different drug classes for common cancer disease sites. METHODS: Drugs entering clinical trials for breast, colorectal, and non-small cell lung cancer were identified using a pharmaceutical business intelligence database. Data regarding drug characteristics, clinical trials, and approval dates were obtained from the database, clinical trial registries, PubMed, and regulatory Web sites. RESULTS: A total of 411 drugs met the inclusion criteria for breast cancer, 246 drugs met the inclusion criteria for colorectal cancer, and 315 drugs met the inclusion criteria for non-small cell lung cancer. Attrition rates were 83.9% for breast cancer, 87.0% for colorectal cancer, and 92.0% for non-small cell lung cancer drugs. In the case of non-small cell lung cancer, there was a trend toward higher attrition rates for targeted monoclonal antibodies compared with other agents. No tumor site-specific differences were noted with regard to cytotoxic chemotherapy, immunomodulatory, or small molecule kinase inhibitor drugs. Drugs classified as "others" in breast cancer had lower attrition rates, primarily due to the higher success of hormonal medications. Mean drug development times were 8.9 years for breast cancer, 6.7 years for colorectal cancer, and 6.6 years for non-small cell lung cancer. CONCLUSIONS: Overall oncologic drug attrition rates remain high, and drugs are more likely to fail in later-stage clinical trials. The refinement of early-phase trial design may permit the selection of drugs that are more likely to succeed in the phase 3 setting. Cancer 2017;123:4672-4679. © 2017 American Cancer Society.

Recent advances in circulating tumor cells and cell-free DNA in metastatic prostate cancer: a review.

INTRODUCTION: The treatment landscape of metastatic prostate cancer has changed dramatically over the past five years. As new discoveries are made and further novel therapies become available, there is a heightened urgency to develop biomarkers that can guide prognoses and predict therapy responses. Circulating tumor cells (CTCs) and cell-free circulating tumor DNA (ctDNA) in the blood have emerged as potential promising tumor avatars. Areas covered: In this review, we describe technological breakthroughs and clinical implementation of the CTCs and ctDNA. We also discuss the key challenges that must be overcome before circulating blood-based biomarkers can be universally adopted into the management of patients with metastatic prostate cancer. Expert commentary: Both CTCs and ctDNA have the potential to be incorporated into routine patient care, with increasing numbers of prospective trials incorporating them into clinical designs. CTCs and ctDNA will thus have an increasingly valuable role in augmenting our understanding of prostate cancer at a molecular level, aiding in prognostication of prostate cancer patients, acting as a surrogate for OS in clinical trials, and helping us prioritize our treatment selections by elucidating resistance mechanisms.

A population-based study of the use of radium 223 in metastatic castration-resistant prostate cancer: Factors associated with treatment completion.

INTRODUCTION: Radium 223 (Ra223) given for six cycles has proven efficacy in clinical trials, but its population-level generalizability has not been well-described. The objectives of this study were to describe population-based Ra223 use in the abiraterone and enzalutamide era and identify factors associated with completion. METHODS: All Ra223 patients at the British Columbia Cancer Agency between September 2013 and February 2016 were identified. Patients who completed <5 vs. ≥5 cycles were compared on patient characteristics, lines of prior therapy, prostate-specific antigen (PSA) and alkaline phosphatase (ALP) decline >30% from baseline (R30%), and survival, to identify factors associated with therapy completion. RESULTS: Ninety-one patients were identified; 48 (52.7%) completed >5 cycles. Median overall survival (mOS) was 10.7 months, PSA and ALP R30% were 21% and 52%, respectively. Completion of <5 cycles was associated with higher baseline ALP (p=0.05) and lower baseline hemoglobin (Hb) levels (p=0.03). Patients in the ≥5 cycles group had longer mOS than those in the <5 cycles group (16.2 vs. 5.9 months; p<0.0001), as well as higher PSA R30% (33.3% vs. 7.0%; p=0.002) and ALP R30% (66.7% vs. 34.9%; p=0.03). Patients with ALP ≥220 and Hb ≤118 had 3.85 times the odds of not completing ≥5 cycles vs. ALP <220 and Hb >118. CONCLUSIONS: Compared to clinical trials, patients in a population-based setting had more lines of therapy and shorter survival. Lower ALP and higher hemoglobin were associated with completion of >5 cycles, longer mOS, and greater incidence of PSA and ALP response.

Sunitinib maintenance therapy after response to docetaxel in metastatic castration resistant prostate cancer (mCRPC).

Background Docetaxel is a standard first-line treatment option for men with metastatic castration resistant prostate cancer (mCRPC). Sunitinib is attractive as a maintenance therapy due to its mechanism of action, oral route of administration, and acceptable toxicity profile. We designed a phase II study of sunitinib in patients with mCRPC who responded to docetaxel. Methods Patients with responding or stable disease at the completion of docetaxel treatment received 50 mg of sunitinib on 4 week on 2 week off cycles. Treatment continued until disease progression (either by RECIST 1.1 criteria or by cancer related symptomatic progression), intolerable toxicity, start of new cancer therapy, withdrawal of consent, or death. The primary endpoint was progression free survival. Secondary endpoints included PSA response rate and safety. Results Twenty-three patients were enrolled and treated. The mean number of prior cycles of docetaxel given was 8.6 (range 4-12). The median number of cycles of sunitinib administered was 4 (range 1-11). Adverse events were generally grade 1-2 with 12 % grade ≥ 3 which were of a type and severity expected for sunitinib. Median PFS was 4.4 months (95 % CI: 1.6-5.1). Most patients had immediate PSA increases without other evidence of disease progression, with the mean increases in PSA over baseline being 197 %, 342 %, and 1437 % in Cycles 1, 2, and 3, respectively. Conclusion Sunitinib was tolerable as maintenance therapy but median PFS was significantly lower than the predefined threshold of 6 months.

Chemotherapy for metastatic castration-sensitive prostate cancer.

Incorporation of docetaxel into metastatic castration-sensitive prostate cancer treatment has added a new treatment option to a disease state that had previously not seen change for decades. Early attempts of a chemo-hormonal approach for castration-sensitive prostate cancer were not successful. With the demonstration of survival benefits using docetaxel in patients with metastatic castration-resistant prostate cancer, this encouraged continued research with docetaxel given earlier in the disease course. Three randomized phase III trials have defined the benefits of docetaxel in the metastatic castration-sensitive prostate cancer setting; however, there remain questions and controversies on the appropriate and optimal patient selection.