Organoid cultures derived from patients with advanced prostate cancer.

The lack of in vitro prostate cancer models that recapitulate the diversity of human prostate cancer has hampered progress in understanding disease pathogenesis and therapy response. Using a 3D organoid system, we report success in long-term culture of prostate cancer from biopsy specimens and circulating tumor cells. The first seven fully characterized organoid lines recapitulate the molecular diversity of prostate cancer subtypes, including TMPRSS2-ERG fusion, SPOP mutation, SPINK1 overexpression, and CHD1 loss. Whole-exome sequencing shows a low mutational burden, consistent with genomics studies, but with mutations in FOXA1 and PIK3R1, as well as in DNA repair and chromatin modifier pathways that have been reported in advanced disease. Loss of p53 and RB tumor suppressor pathway function are the most common feature shared across the organoid lines. The methodology described here should enable the generation of a large repertoire of patient-derived prostate cancer lines amenable to genetic and pharmacologic studies.

Replication competent retrovirus testing (RCR) in the National Gene Vector Biorepository: No evidence of RCR in 1,595 post-treatment peripheral blood samples obtained from 60 clinical trials.

The clinical impact of any therapy requires the product be safe and effective. Gammaretroviral vectors pose several unique risks, including inadvertent exposure to replication competent retrovirus (RCR) that can arise during vector manufacture. The US FDA has required patient monitoring for RCR, and the National Gene Vector Biorepository is an NIH resource that has assisted eligible investigators in meeting this requirement. To date, we have found no evidence of RCR in 338 pre-treatment and 1,595 post-treatment blood samples from 737 patients associated with 60 clinical trials. Most samples (75%) were obtained within 1 year of treatment, and samples as far out as 9 years after treatment were analyzed. The majority of trials (93%) were cancer immunotherapy, and 90% of the trials used vector products produced with the PG13 packaging cell line. The data presented here provide further evidence that current manufacturing methods generate RCR-free products and support the overall safety profile of retroviral gene therapy.

Immunotherapy combinations for metastatic castration-resistant prostate cancer - failed trials and future aspects.

PURPOSE OF REVIEW: Immunotherapy, a treatment modality currently synonymous with immune checkpoint blockade remains a challenge for prostate cancer. Despite multiple phase 3 trials using checkpoint inhibitors in combinatorial approaches, there have been no benefits to date in overall survival or radiographic progression free survival. However, newer strategies prevail that are directed to a variety of unique cell surface antigens. These strategies include unique vaccines, chimeric antigen receptor (CAR) T, bispecific T cell engager platforms, and antibody-drug conjugates. RECENT FINDINGS: New antigens are being targeted by various immunologic strategies. These antigens are pan-carcinoma as they may be expressed on a variety of cancers but remains effective targets for therapeutic attack. SUMMARY: Immunotherapy with checkpoint inhibitors alone or in combination with a variety of agents such as chemotherapy, poly-ADP ribose polymerase (PARP) inhibitors or novel biologics have met with failure in the endpoints of overall survival (OS) and radiographic progresson-free survival (rPFS). Despite these efforts, other immunologic efforts to develop unique tumor-targeted strategies should be continued.

Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Prostate Cancer: The Primary Results of the PRONOUNCE Randomized Trial.

BACKGROUND: The relative cardiovascular safety of gonadotropin-releasing hormone (GnRH) antagonists compared with GnRH agonists in men with prostate cancer and known atherosclerotic cardiovascular disease remains controversial. METHODS: In this international, multicenter, prospective, randomized, open-label trial, men with prostate cancer and concomitant atherosclerotic cardiovascular disease were randomly assigned 1:1 to receive the GnRH antagonist degarelix or the GnRH agonist leuprolide for 12 months. The primary outcome was the time to first adjudicated major adverse cardiovascular event (composite of death, myocardial infarction, or stroke) through 12 months. RESULTS: Because of slower-than-projected enrollment and fewer-than-projected primary outcome events, enrollment was stopped before the 900 planned participants were accrued. From May 3, 2016, to April 16, 2020, a total of 545 patients from 113 sites across 12 countries were randomly selected. Baseline characteristics were balanced between study groups. The median age was 73 years, 49.8% had localized prostate cancer; 26.3% had locally advanced disease, and 20.4% had metastatic disease. A major adverse cardiovascular event occurred in 15 (5.5%) patients assigned to degarelix and 11 (4.1%) patients assigned to leuprolide (hazard ratio, 1.28 [95% CI, 0.59-2.79]; P=0.53). CONCLUSIONS: PRONOUNCE (A Trial Comparing Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Advanced Prostate Cancer and Cardiovascular Disease) is the first, international, randomized clinical trial to prospectively compare the cardiovascular safety of a GnRH antagonist and a GnRH agonist in patients with prostate cancer. The study was terminated prematurely because of the smaller than planned number of participants and events, and no difference in major adverse cardiovascular events at 1 year between patients assigned to degarelix or leuprolide was observed. The relative cardiovascular safety of GnRH antagonists and agonists remains unresolved. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02663908.

Clinical annotations for prostate cancer research: Defining data elements, creating a reproducible analytical pipeline, and assessing data quality.

BACKGROUND: Routine clinical data from clinical charts are indispensable for retrospective and prospective observational studies and clinical trials. Their reproducibility is often not assessed. We developed a prostate cancer-specific database for clinical annotations and evaluated data reproducibility. METHODS: For men with prostate cancer who had clinical-grade paired tumor-normal sequencing at a comprehensive cancer center, we performed team-based retrospective data collection from the electronic medical record using a defined source hierarchy. We developed an open-source R package for data processing. With blinded repeat annotation by a reference medical oncologist, we assessed data completeness, reproducibility of team-based annotations, and impact of measurement error on bias in survival analyses. RESULTS: Data elements on demographics, diagnosis and staging, disease state at the time of procuring a genomically characterized sample, and clinical outcomes were piloted and then abstracted for 2261 patients (with 2631 samples). Completeness of data elements was generally high. Comparing to the repeat annotation by a medical oncologist blinded to the database (100 patients/samples), reproducibility of annotations was high; T stage, metastasis date, and presence and date of castration resistance had lower reproducibility. Impact of measurement error on estimates for strong prognostic factors was modest. CONCLUSIONS: With a prostate cancer-specific data dictionary and quality control measures, manual clinical annotations by a multidisciplinary team can be scalable and reproducible. The data dictionary and the R package for reproducible data processing are freely available to increase data quality and efficiency in clinical prostate cancer research.

American Cancer Society prostate cancer survivorship care guidelines.

Prostate cancer survivors approach 2.8 million in number and represent 1 in 5 of all cancer survivors in the United States. While guidelines exist for timely treatment and surveillance for recurrent disease, there is limited availability of guidelines that facilitate the provision of posttreatment clinical follow-up care to address the myriad of long-term and late effects that survivors may face. Based on recommendations set forth by a National Cancer Survivorship Resource Center expert panel, the American Cancer Society developed clinical follow-up care guidelines to facilitate the provision of posttreatment care by primary care clinicians. These guidelines were developed using a combined approach of evidence synthesis and expert consensus. Existing guidelines for health promotion, surveillance, and screening for second primary cancers were referenced when available. To promote comprehensive follow-up care and optimal health and quality of life for the posttreatment survivor, the guidelines address health promotion, surveillance for prostate cancer recurrence, screening for second primary cancers, long-term and late effects assessment and management, psychosocial issues, and care coordination among the oncology team, primary care clinicians, and nononcology specialists. A key challenge to the development of these guidelines was the limited availability of published evidence for management of prostate cancer survivors after treatment. Much of the evidence relies on studies with small sample sizes and retrospective analyses of facility-specific and population databases.

Evolving understanding and categorization of prostate cancer: preventing progression to metastatic castration-resistant prostate cancer: RADAR IV.

INTRODUCTION To interpret data and update the traditional categorization of prostate cancer in order to help treating clinicians make more informed decisions. These updates include guidance regarding how to best use next generation imaging (NGI) with the caveat that the new imaging technologies are still a work in progress. MATERIALS AND METHODS: Literature review. RESULTS: Critical goals in prostate cancer management include preventing or delaying emergence of distant metastases and progression to castration-resistant disease. Pathways for progression to metastatic castration-resistant prostate cancer (mCRPC) involve transitional states: nonmetastatic castration-resistant prostate cancer (nmCRPC), metastatic hormone-sensitive prostate cancer (mHSPC), and oligometastatic disease. Determination of clinical state depends in part on available imaging modalities. Currently, fluciclovine and gallium-68 (68Ga) prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) are the NGI approaches with the most favorable combination of availability, specificity, and sensitivity. PET imaging can be used to help guide treatment selection in most patients. NGI can help determine patients who are candidates for new treatments, most notably (next-generation androgen antagonists, eg, apalutamide, enzalutamide, darolutamide), that can delay progression to advanced disease. CONCLUSIONS: It is important to achieve a consensus on new and more easily understood terminology to clearly and effectively describe prostate cancer and its progression to health care professionals and patients. It is also important that description of disease states make clear the need to initiate appropriate treatment. This may be particularly important for disease in transition to mCRPC.

A phase 2 trial of abiraterone acetate without glucocorticoids for men with metastatic castration-resistant prostate cancer.

BACKGROUND: Abiraterone acetate suppresses adrenal androgens and glucocorticoids through the inhibition of CYP17; however, given the risk of mineralocorticoid excess, it is administered with glucocorticoids. Herein, the authors performed a phase 2, single-arm study that was designed to assess the safety of abiraterone acetate without steroids in patients with castration-resistant prostate cancer. METHODS: Eligible patients had castration-resistant prostate cancer with controlled blood pressure and normal potassium. Patients initially received abiraterone acetate at a dose of 1000 mg daily alone. Those with persistent or severe mineralocorticoid toxicity received treatment with prednisone initiated at a dose of 5 mg twice daily. Therapy was continued until radiographic progression, toxicity, or withdrawal. The primary objective of the current study was to determine the percentage of men requiring prednisone to manage mineralocorticoid toxicity. Toxicity was graded according to Common Terminology Criteria for Adverse Events, version 4.0. RESULTS: A total of 58 patients received at least 1 dose of abiraterone acetate; the majority had metastases (53 patients; 91.4%). Sixteen patients (27.6%) received prior chemotherapy, 6 patients (10.3%) received prior enzalutamide, and 4 patients (7%) received prior ketoconazole. Grade 3 to 4 adverse events of interest included hypertension (9 patients; 15.5%) and hypokalemia (4 patients; 7%). There was no grade ≥3 edema. Seven patients (12%) initiated prednisone therapy for mineralocorticoid toxicity, 3 patients for hypertension (5%), and 4 patients for hypokalemia (7%). Two patients initiated prednisone therapy for fatigue (3%). Forty patients (68%) experienced a decline in prostate-specific antigen of ≥50% with the use of abiraterone acetate alone. Patients with lower baseline levels of androstenedione (P = .04), androsterone (P = .01), dehydroepiandrosterone (P = .03), and 17-hydroxyprogesterone (P = .03) were found to be more likely to develop mineralocorticoid toxicity. CONCLUSIONS: Treatment with abiraterone acetate without steroids is feasible, although clinically significant adverse events can occur in a minority of patients. The use of abiraterone acetate without prednisone should be balanced with the potential for toxicity and requires close monitoring.

A Clinician's Guide to Next Generation Imaging in Patients With Advanced Prostate Cancer (RADAR III).

PURPOSE: The advanced prostate cancer therapeutic landscape has changed dramatically in the last several years, resulting in improved overall survival of patients with castration naïve and castration resistant disease. The evolution and development of novel next generation imaging techniques will affect diagnostic and therapeutic decision making. Clinicians must navigate when and which next generation imaging techniques to use and how to adjust treatment strategies based on the results, often in the absence of correlative therapeutic data. Therefore, guidance is needed based on best available information and current clinical experience. MATERIALS AND METHODS: The RADAR (Radiographic Assessments for Detection of Advanced Recurrence) III Group convened to offer guidance on the use of next generation imaging to stage prostate cancer based on available data and clinical experience. The group also discussed the potential impact of next generation imaging on treatment options based on earlier detection of disease. RESULTS: The group unanimously agreed that progression to metastatic disease is a seminal event for patient treatment. Next generation imaging techniques are able to detect previously undetectable metastases, which could redefine the phases of prostate cancer progression. Thus, earlier systemic or locally directed treatment may positively alter patient outcomes. CONCLUSIONS: The RADAR III Group recommends next generation imaging techniques in select patients in whom disease progression is suspected based on laboratory (biomarker) values, comorbidities and symptoms. Currently 18F-fluciclovine and 68Ga prostate specific membrane antigen positron emission tomography/computerized tomography are the next generation imaging agents with a favorable combination of availability, specificity and sensitivity. There is ongoing research of additional next generation imaging technologies, which may offer improved diagnostic accuracy and therapeutic options. As next generation imaging techniques evolve and presumably result in improved global accessibility, clinician ability to detect micrometastases may be enhanced for decision making and patient outcomes.

A phase I study of the antibody drug conjugate ASG-5ME, an SLC44A4-targeting antibody carrying auristatin E, in metastatic castration-resistant prostate cancer.

Background Antibody drug conjugates (ADC) offer the potential of maximizing efficacy while minimizing systemic toxicity. ASG-5ME, an SLC44A4-targeting antibody carrying monomethyl auristatin E (MMAE), a microtubule-disrupting agent, was investigated in men with metastatic castration resistant prostate cancer. Methods The primary objective of this phase I study was to determine maximum tolerated dose (MTD) and recommended phase II dose. Secondary objectives were safety, antitumor activity, pharmacokinetic properties, immunogenicity, and the detection of SLC44A4 on circulating tumor cells. Patients (pts) were treated among 7 dose levels every 21 days. A dose expansion phase enrolled 20 additional pts. at the MTD. Results Twenty-six and 20 pts. were treated in dose escalation and dose expansion cohorts respectively. The MTD was 2.7 mg/kg. Dose-limiting toxicities occurred in 4 pts.: grade 3 fatigue (n = 1); grade 3 abdominal pain, diarrhea and fatigue (n = 1); grade 4 neutropenia and hyponatremia and grade 3 maculopapular rash, constipation and hypoxia (n = 1); grade 3 troponin elevation without cardiac sequelae (n = 1). Fatigue and diarrhea were the most prevalent adverse events (AEs) across all cycles. Two grade 5 AEs occurred in the dose expansion cohort, each after 1 dose: 1 pt. developed grade 3 hyperglycemia, renal insufficiency and leukopenia; 1 pt. developed grade 3 hyperglycemia complicated by bacteremia. Free MMAE levels did not accumulate with repeat dosing. Of evaluable pts., 52% had either stable disease or a partial response. Conclusions Further development of ASG-5ME is not being pursued due to its narrow therapeutic index. Some toxicities were potentially related to on-target effects on normal tissue expressing the SLC44A4 protein. However, other toxicities were consistent with studies of previous MMAE-containing ADCs. Unconjugated MMAE is a less likely etiology based on prior data.

Sipuleucel-T: When and for Whom to Recommend It.

Multiple immunotherapy platforms have been investigated for prostate cancer, but sipuleucel-T still remains the sole approved autologous cellular immune product that can be used in men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer. While preliminary data for specific checkpoint inhibitors suggest benefit for some patients, leading to durable responses, it has been clear that sipuleucel-T can affect not only the intratumoral milieu but also systemic immune populations. This means that the immune system can respond to sipuleucel-T in such a way that it may also effect an immunomodulatory response to other current and future treatments. It is clear that sipuleucel-T is here to stay; nevertheless, efforts to enhance its efficacy continue. A challenge that continues to be investigated is the question of how and when to use this immune therapy as part of the current continuum of competing approved agents.

Immunotherapy for prostate cancer: is prostate an immune responsive tumor?

PURPOSE OF REVIEW: The purpose of this review is to identify possible reasons why prostate cancer suboptimally responds to immune therapies. RECENT FINDINGS: Interrogation of the intraprostatic milieu suggests that within the normal prostate, foci of tumor can be surrounded by inflammatory cells that may or may not represent foci of immune sensitivity. Whether or not these cells are specific 'immune responders' depends on a multiplicity of factors within the host and intratumoral/stromal milieu. Solid tumors such as kidney and melanoma can undergo spontaneous regressions alone or upon removal of a primary mass lesion, suggestive of some sort of immune derepression once the original lesion is removed. Such observations, though rare, suggest that some unknown immunologic process may be governing how the tumor behaves. Similarly, in melanoma, there are rare abscopal effects suggesting that once a primary lesion is radiated, a secondary lesion afar from the treated lesion could remit. SUMMARY: Why prostate cancer remains an immunologic conundrum remains a mystery. Patients with metastatic prostate cancer have a survival benefit but minimal or no antitumor response with the autologous cellular product immune therapy, sipuleucel-T, whereas checkpoint inhibitors, successful in melanoma, renal cell, nonsmall cell lung, and urothelial cancers, have little or no activity. This review serves to bring to the forefront the issues that may underlie why prostate cancer is not robustly responsive to immune strategies.

Immunotherapy in metastatic prostate cancer.

INTRODUCTION: Prostate cancer remains a challenge as a target for immunological approaches. The approval of the first cell-based immune therapy, Sipuleucel-T for prostate cancer introduced prostate cancer as a solid tumor with the potential to be influenced by the immune system. METHODS: We reviewed articles on immunological management of prostate cancer and challenges that lie ahead for such strategies. RESULTS: Treatments have focused on the identification of novel cell surface antigens thought to be unique to prostate cancer. These include vaccines against carbohydrate and blood group antigens, xenogeneic and naked DNA vaccines, and pox viruses used as prime-boost or checkpoint inhibitors. No single vaccine construct to date has resulted in a dramatic antitumor effect. The checkpoint inhibitor, anti-CTLA-4 has resulted in several long-term remissions, but phase III trials have not demonstrated an antitumor effect or survival benefit. CONCLUSIONS: Multiple clinical trials suggest that prostate cancer may not be optimally treated by single agent immune therapies and that combination with biologic agents, chemotherapies, or radiation may offer some enhancement of benefit.

Development of thyroglobulin antibodies after GVAX immunotherapy is associated with prolonged survival.

Cancer immunotherapy induces a variety of autoinflammatory responses, including those against the thyroid gland, which can be exploited to predict clinical outcomes. Considering the paucity of information about thyroid autoimmunity in patients receiving cancer vaccines, we designed our study to assess the development of thyroglobulin antibodies (TgAbs) in patients treated with GVAX (vaccine made of a tumor cell type transfected with GM-CSF) and/or ipilimumab and correlated seroconversion with survival. Using both in house and commercial ELISA assays, we measured TgAbs in patients with pancreatic (No. = 53), prostate (No. = 35) or colon (No. = 8) cancer, before and after treatment with GVAX only (No. = 34), GVAX plus ipilimumab (No. = 42) or ipilimumab (No. = 20), and correlated their levels with patient's survival, disease status and T-cell surface markers. Antibodies to thyroperoxidase, myeloperoxidase, proteinase 3, insulin and actin were also measured. TgAbs specifically developed after GVAX, independent of the underlying cancer (81% in prostate, 75% colon cancer and 76% pancreatic cancer) and co-administration of ipilimumab (75% in GVAX only and 78% in GVAX plus ipilimumab). This TgAbs seroconversion could be detected mainly by the in house assay, suggesting that the thyroglobulin epitopes recognized by the antibodies induced by GVAX are different from the epitopes seen in the classic form of Hashimoto thyroiditis. Notably, TgAbs seroconversion was associated with significantly prolonged survival (p = 0.01 for pancreas and p = 0.005 for prostate cancer). In conclusion, GVAX immunotherapy induces the appearance of TgAbs that recognize a unique antigenic repertoire and associate with prolonged survival.

Everolimus combined with gefitinib in patients with metastatic castration-resistant prostate cancer: Phase 1/2 results and signaling pathway implications.

BACKGROUND: The effects of mammalian target of rapamycin (mTOR) inhibition are limited by feedback reactivation of receptor tyrosine kinase signaling in phosphatase and tensin homolog-null tumors. Thus, this study tested the combination of mTOR inhibition (everolimus) and epidermal growth factor receptor inhibition (gefitinib) in castration-resistant prostate cancer (CRPC). METHODS: In phase 1, 12 patients (10 with CRPC and 2 with glioblastoma) received daily gefitinib (250 mg) with weekly everolimus (30, 50, or 70 mg). In phase 2, 27 CRPC patients received gefitinib with everolimus (70 mg). RESULTS: Phase 1 revealed no pharmacokinetic interactions and no dose-limiting toxicities. In phase 2, 18 of 27 patients (67%) discontinued treatment before the 12-week evaluation because of progression as evidenced by prostate-specific antigen (PSA) levels (n = 6) or imaging (n = 5) or because of a grade 2 or higher toxicity (n = 7). Thirteen of the 37 CRPC patients (35%) exhibited a rapidly rising PSA level after they had begun treatment, and this declined upon discontinuation. Fluorodeoxyglucose positron emission tomography 24 to 72 hours after the initiation of treatment showed a decrease in the standardized uptake value consistent with mTOR inhibition in 27 of the 33 evaluable patients (82%); there was a corresponding rise in PSA in 20 of these 27 patients (74%). CONCLUSIONS: The combination of gefitinib and everolimus did not result in significant antitumor activity. The induction of PSA in tumors treated with mTOR inhibitors was consistent with preclinical data showing that phosphoinositide 3-kinase (PI3K) pathway signaling feedback inhibits the androgen receptor (AR). This clinical evidence of relief of feedback inhibition promoting enhanced AR activity supports future studies combining PI3K pathway inhibitors and second-generation AR inhibitors in CRPC.

Targeting DNA repair with combination veliparib (ABT-888) and temozolomide in patients with metastatic castration-resistant prostate cancer.

Androgen receptor-mediated transcription is directly coupled with the induction of DNA damage, and castration-resistant tumor cells exhibit increased activity of poly (ADP-ribose) polymerase (PARP)-1, a DNA repair enzyme. This study assessed the efficacy and safety of low dose oral PARP inhibitor veliparib (ABT-888) and temozolomide (TMZ) in docetaxel-pretreated patients with metastatic castration-resistant prostate cancer (mCRPC) in a single-arm, open-label, pilot study. Patients with mCRPC progressing on at least one docetaxel-based therapy and prostate specific antigen (PSA) ≥ 2 ng/mL were treated with veliparib 40 mg twice daily on days 1-7 and TMZ once daily (150 mg/m(2)/day cycle 1; if well tolerated then 200 mg/m(2)/day cycle 2 onwards) on days 1-5 q28 days. Patients received 2 (median) treatment cycles (range, 1-9). The primary endpoint was confirmed PSA response rate (decline ≥ 30 %). Twenty-six eligible patients were enrolled, 25 evaluable for PSA response. Median baseline PSA was 170 ng/mL. Two patients had a confirmed PSA response (8.0 %; 95 % CI: 1.0-26.0), 13 stable PSA, and 10 PSA progression. The median progression-free survival was 9 weeks (95 % CI: 7.9-17) and median overall survival 39.6 weeks (95 % CI: 26.6-not estimable). The most frequent treatment-emergent adverse events (AEs) were thrombocytopenia (77 %), anemia (69 %), fatigue (50 %), neutropenia (42 %), nausea (38 %), and constipation (23 %). Grade 3/4 AEs occurring in > 10 % of patients were thrombocytopenia (23 %) and anemia (15 %). Veliparib and TMZ combination was well tolerated but with modest activity. Biomarker analysis supported the proof of concept that this combination has some antitumor activity in mCRPC.

Microsatellite Instability, Tumor Mutational Burden, and Response to Immune Checkpoint Blockade in Patients with Prostate Cancer.

PURPOSE: Patients with microsatellite instability high/mismatch repair deficient (MSI-H/dMMR) and high tumor mutational burden (TMB-H) prostate cancers are candidates for pembrolizumab. We define the genomic features, clinical course, and response to immune checkpoint blockade (ICB) in patients with MSI-H/dMMR and TMB-H prostate cancers without MSI (TMB-H/MSS). METHODS: We sequenced 3,244 tumors from 2,257 prostate cancer patients. MSI-H/dMMR prostate cancer was defined as MSIsensor score ≥10 or MSIsensor score ≥3 and <10 with a deleterious MMR alteration. TMB-H was defined as ≥10 mutations/megabase. PSA50 and RECIST responses were assigned. Overall survival (OS) and radiographic progression-free survival (rPFS) were compared using log rank test. RESULTS: 63 (2.8%) men had MSI-H/dMMR and 33 (1.5%) had TMB-H/MSS prostate cancers. Patients with MSI-H/dMMR and TMB-H/MSS tumors more commonly presented with grade group 5 and metastatic disease at diagnosis. MSI-H/dMMR tumors had higher TMB, indel and neoantigen burden compared with TMB-H/MSS. 27 patients with MSI-H/dMMR and 8 patients with TMB-H/MSS tumors received ICB, none of whom harbored POLE mutations. 45% of MSI-H/dMMR patients had a RECIST response and 65% had a PSA50 response. No TMB-H/MSS patient had a RECIST response and 50% had a PSA50 response. rPFS tended to be longer in MSI-H/dMMR patients than in TMB-H/MSS patients who received immunotherapy. Pronounced differences in genomics, TMB or MSIsensor score were not detected between MSI-H/dMMR responders and non-responders. CONCLUSIONS: MSI-H/dMMR prostate cancers have greater TMB, indel and neoantigen burden compared with TMB-H/MSS prostate cancers, and these differences may contribute to more profound and durable responses to ICB.

Repetitively dosed docetaxel and ¹5³samarium-EDTMP as an antitumor strategy for metastatic castration-resistant prostate cancer.

BACKGROUND: ß-emitting bone-seeking radiopharmaceuticals have historically been administered for pain palliation whereas docetaxel prolongs life in patients with metastatic castration-resistant prostate cancer (mCRPC). In combination, these agents simultaneously target the bone stroma and cancer cell to optimize antitumor effects. The toxicity and efficacy when each agent is combined at full, recommended doses, in a repetitive fashion is not well established. METHODS: Patients with progressive mCRPC and ≥ 3 bone lesions received (153) Sm-EDTMP (samarium-153 ethylene diamine tetramethylene phosphonate) at a dose of 1.0 mCi/kg every 9 weeks and docetaxel at a dose of 75 mg/m(2) every 3 weeks. In the absence of unacceptable toxicity, patients were allowed to continue additional cycles, defined by 9 weeks of treatment, until intolerance or biochemical/radiographic disease progression. RESULTS: Of the 30 patients treated, approximately 50% were considered to be taxane-naive, 36.7% were taxane-refractory, and 13.3% had previously been exposed to taxanes but were not considered refractory. Patients received on average 2.5 cycles of treatment (6.5 doses of docetaxel and 2.5 doses of (153) Sm-EDTMP). Twelve patients (40%) demonstrated a decline in their prostate-specific antigen level of ≥ 50%. The median progression-free survival (biochemical or radiographic) was 7.0 months and the overall survival was 14.3 months. Nine patients (30%) did not recover platelet counts >100 K/mm(3) after a median of 3 cycles to allow for additional treatment, with 4 patients experiencing prolonged thrombocytopenia. The most common reasons for trial discontinuation were progressive disease and hematologic toxicity. CONCLUSIONS: The results of the current study indicate that (153) Sm-EDTMP can be safely combined with docetaxel at full doses on an ongoing basis in patients with mCRPC. Although thrombocytopenia limited therapy for some patients, preliminary efficacy supports the strategy of combining a radiopharmaceutical with chemotherapy, which is an appealing strategy given the anticipated availability of α emitters that can prolong survival.

Phase I pharmacokinetic and biodistribution study with escalating doses of ²²³Ra-dichloride in men with castration-resistant metastatic prostate cancer.

PURPOSE: ²²³Ra-Dichloride (²²³Ra) is a novel bone-seeking alpha-emitter that prolongs survival in patients with castration-resistant metastatic prostate cancer. We conducted a study to better profile the pharmacokinetics, pharmacodynamics, and biodistribution of this agent. METHODS: Ten patients received either 50, 100, or 200 kBq of ²²³Ra per kilogram of body weight. Subsequently, six of these ten patients received a second dose of 50 kBq/kg. Pharmacokinetics and biodistribution were assessed by serial blood sampling, planar imaging, and whole-body counting. Pharmacodynamic assessment was based on measurements of prostate-specific antigen, bone alkaline phosphatase, and serum N-telopeptide. Safety was also assessed. RESULTS: Pharmacokinetic studies showed rapid clearance of ²²³Ra from the vasculature, with a median of 14% (range 9-34%), 2% (range 1.6-3.9%), and 0.5% (range 0.4-1.0%) remaining in plasma at the end of infusion, after 4 h, and after 24 h, respectively. Biodistribution studies showed early passage into the small bowel and subsequent fecal excretion with a median of 52% of administered ²²³Ra in the bowel at 24 h. Urinary excretion was relatively minor (median of 4% of administered ²²³Ra). Bone retention was prolonged. No dose-limiting toxicity was observed. Pharmacodynamic effects were observed (alkaline phosphatase and serum N-telopeptides) in a significant fraction of patients. CONCLUSION: ²²³Ra cleared rapidly from plasma and rapidly transited into small bowel, with fecal excretion the major route of elimination. Administered activities up to 200 kBq/kg were associated with few side effects and appeared to induce a decline in serum indicators of bone turnover.

Genomic Portraits: Reflections into a Tumor's Response to Therapy.

Well-annotated matched tissue specimens both before and after initiation of androgen receptor signaling inhibitors (ARSI) have revealed activation of unique signaling pathways and genomic signatures that identify a profile to guide therapy. A recent study represents the largest prospective biospecimen banking protocol to study mechanisms of resistance to ARSIs. See related article by Menssouri et al., p. 4504.