Dorff, Tanya B.

PURPOSE Patients with biochemically recurrent prostate cancer (BRPC) after radical prostatectomy and a short PSA doubling time are at risk for distant metastases. Apalutamide, an androgen receptor antagonist, and abiraterone acetate plus prednisone (AAP) prolong survival in the metastatic setting. We evaluated whether intensification of androgen-deprivation therapy (ADT) improves outcomes in BRPC. PATIENTS AND METHODS PRESTO is a randomized phase III, open-label trial in patients with BRPC and PSA doubling time ≤9 months (ClinicalTrials.gov identifier: NCT03009981 ). Patients were randomly assigned 1:1:1 to receive a finite 52-week treatment course with ADT control, ADT + apalutamide, or ADT + apalutamide + AAP. The primary end point was PSA progression-free survival (PSA-PFS), defined as serum PSA >0.2 ng/mL after treatment completion. RESULTS Five hundred three patients were enrolled. The median PSA was 1.8 ng/mL (IQR, 1.0-3.6). At the first planned interim analysis, both experimental arms significantly prolonged PSA-PFS compared with the control arm (median, 24.9 months for ADT + apalutamide v 20.3 months for ADT; hazard ratio [HR], 0.52 [95% CI, 0.35 to 0.77]; P = .00047; median, 26.0 months for ADT + apalutamide + AAP v 20.0 months for ADT; HR, 0.48 [95% CI, 0.32 to 0.71]; P = .00008). Median time to testosterone recovery did not differ across treatment arms. The most common grade ≥3 adverse event was hypertension (7.5%, 7.4%, and 18% in ADT, ADT + apalutamide, and ADT + apalutamide + AAP arms, respectively). CONCLUSION Intensified AR blockade for a finite duration prolongs PSA-PFS with a manageable safety profile, without adversely affecting time to testosterone recovery. The addition of apalutamide to ADT should be considered in patients with high-risk BRPC.

The NCCN Guidelines for Prostate Cancer provide a framework on which to base decisions regarding the workup of patients with prostate cancer, risk stratification and management of localized disease, post-treatment monitoring, and treatment of recurrence and advanced disease. The Guidelines sections included in this article focus on the management of metastatic castration-sensitive disease, nonmetastatic castration-resistant prostate cancer (CRPC), and metastatic CRPC (mCRPC). Androgen deprivation therapy (ADT) with treatment intensification is strongly recommended for patients with metastatic castration-sensitive prostate cancer. For patients with nonmetastatic CRPC, ADT is continued with or without the addition of certain secondary hormone therapies depending on prostate-specific antigen doubling time. In the mCRPC setting, ADT is continued with the sequential addition of certain secondary hormone therapies, chemotherapies, immunotherapies, radiopharmaceuticals, and/or targeted therapies. The NCCN Prostate Cancer Panel emphasizes a shared decision-making approach in all disease settings based on patient preferences, prior treatment exposures, the presence or absence of visceral disease, symptoms, and potential side effects.

5077 Background: In the phase 3 PRESTO study, intensified androgen deprivation therapy (ADT) with apalutamide (Apa) with or without abiraterone acetate plus prednisone (AAP), administered for a finite treatment period of 52 weeks, prolonged prostate-specific antigen progression-free survival (PSA PFS) in pts with high-risk biochemically relapsed prostate cancer (BRPC). We evaluated the association between PSA nadir within 3 months of treatment initiation with subsequent PSA PFS in this study. Methods: PRESTO is a randomized phase 3, open-label trial in pts with BRPC following radical prostatectomy (RP) and PSA doubling time (PSADT) ≤ 9 months, without distant metastases on conventional imaging (NCT03009981). Pts were randomized 1:1:1 to receive a finite 52-week treatment course with ADT, ADT + Apa, or ADT + Apa + AAP, stratified by PSADT (< 3 vs 3–9 months), with post-treatment follow-up. The association between PSA nadir within the first three months on treatment with subsequent PSA PFS was analyzed in a post hoc fashion. Results: 504 pts were randomized to ADT alone (N = 167), ADT + Apa (N = 168) or ADT + Apa + AAP (N = 169). 463 pts were evaluable for PSA nadir at 3 months. Across the three treatment arms, a PSA nadir of less than 0.1, between 0.1 – 0.2, and ≥ 0.2 ng/mL within the first three months of treatment was observed in 86.3%, 4.4%, and 9.3% of patients, respectively. A PSA nadir of < 0.2 ng/mL was reached within 3 months of treatment initiation in 79.8%, 96.9%, and 95.0% of pts randomized to the ADT, ADT + Apa, and ADT + Apa + AAP arms, respectively. The association between time to PSA nadir and subsequent PSA PFS was -0.30 (standard error = 0.03, Kendall’s tau modified for bivariate censoring), and median time to PSA nadir was 2.0 months (interquartile range 1.12 – 4.76 months). Failure to reach a PSA nadir < 0.2 ng/mL within the first three months of treatment was associated with a significantly shorter PSA PFS compared to pts with a PSA nadir ≤ 0.1 ng/mL (median PSA PFS of 13.9 vs. 22.8 months from 3 months post-treatment initiation; hazard ratio = 5.60, 95% CI: 3.58 – 8.75, p < 0.0001). There was also a significant difference in PSA PFS in those with a three-month PSA nadir between 0.1 – 0.2 vs ≤ 0.1 ng/mL (median PSA PFS 17.4 vs 22.8 months, HR = 2.63, 95:CI: 1.49 – 4.63, p = 0.0008). Conclusions: Using a landmark analysis at 3 months, a failure to reach PSA nadir less than 0.1 ng/mL within three months following initiation of ADT in BRPC is associated with shorter time to subsequent progression following treatment discontinuation. Follow-up is ongoing to integrate genomic profiling of primary prostate cancer tissues and whole blood RNA in pts with suboptimal PSA nadir to identify potential markers of relative androgen pathway inhibitor resistance. Clinical trial information: NCT03009981 .

5074 Background: Analysis of phase 3 studies of patients (pts) with mHSPC in the era of ADT, including in combination with docetaxel and/or androgen receptor axis targeted therapies have established PSA-7mo as a key prognostic marker. Our objective was to evaluate the association between PSA-3mo, PSA 7-mo and OS measured in the phase 3 S1216 trial in mHSPC comparing ADT + orteronel (treatment arm) vs ADT + bicalutamide (control arm) [NCT01809691]. Methods: Pts enrolled in the S1216 trial with available PSA-3mo & PSA-7mo were included in this analysis. PSA responses were defined as complete response (CR) if PSA ≤ 0.2 ng/mL, partial response (PR) for PSA >0.2 and ≤ 4ng/mL, and no response (NR) as PSA >4 ng/mL at month 3 or 7. Landmark OS was measured and Cox regression model applied adjusting for stratification (performance status, extent of disease, early vs late start of treatment, treatment arm). Results: 1251 pts were alive and evaluable for PSA-3mo and 1231 pts were evaluable at 7 mo, out of a total of 1279 pts. The median age was 67 (range: 43-92), 10% of patients were black, 96% had a Zubrod performance status of 0-1. Median PSA at baseline was 29 ng/ml (range: 2-6710). Of pts on treatment vs.control arm, PSA-3mo CR, PR, and NR occurred in 52% vs 35%; 31% vs 42%, and 17% vs 23%, respectively. Of pts on treatment vs control arm, PSA-7mo CR, PR, and NR occurred in 61% vs 46%, 20% vs 26%, and 19% vs 29%, respectively. CR or PR at either timepoint led to significantly better outcomes than those with NR. No interaction between treatment arm and PSA response was observed in terms of OS. Conclusions: PSA-3mo and PSA-7mo are strong prognostic markers for pts with mHSPC. More pts on ADT with orteronel achieved CR at 3 and 7 mo. In addition to its use in counseling patients in the clinic, PSA-3mo and PSA-7mo may be used as parameters for designing future trials in pts with mHSPC, utilizing the next generation of intensification or de-intensification treatment regimens. Clinical trial information: NCT01809691 . [Table: see text]

TPS292 Background: PT-112 is a novel small I-O molecule currently in development for several cancers. Preclinical studies have shown the robust induction of immunogenic cell death by PT-112, leading to an anti-cancer adaptive immune response. Biodistribution experiments in mice showed PT-112’s partial bone affinity. In two prior phase I studies, late-line metastatic castration-resistant prostate cancer patients (mCRPC pts) were treated with evidence of anti-cancer activity, including tumor volume reductions, improvements in PET and bone scans, PSA and alkaline phosphatase (ALP) reductions, and anecdotal cases of improvement in disease-related pain. This, taken together with the immunogenic and osteotropic properties observed in preclinical work, provided a strong rationale to further explore PT-112 in mCRPC, an immunologically “cold” disease with a high prevalence of bone metastases. Moreover, in an analysis of >6,000 mCRPC pts, circulating tumor cell (CTC) declines (CTC0 and CTC conversions) were correlated with improvements in survival to a greater extent than PSA declines (PSA50) (Heller et al., JCO, 36:6 2017), prompting incorporation of CTC changes as a secondary endpoint. Methods: The primary objective of the study is to define the dose regimen of PT-112 for pivotal study. Pts are randomized to one of three arms, receiving IV PT-112 on 28-day cycles via one hour infusions on (1) Days 1 and 15 at 250 mg/m2, (2) Days 1 and 15 at 360 mg/m2, or (3) Days 1 and 15 of cycle 1 at 360 mg/m2 followed by 250 mg/m2 on Day 15 of subsequent cycles. Key eligibility criteria include radiographically progressive disease at study entry; ≥3 life-prolonging therapies for metastatic disease including 1-2 taxanes, ≥1 new generation anti-androgen therapies, and other drugs FDA approved on the basis of survival; and allowing bone-only metastatic disease. Efficacy assessments comprise disease control rate at 4 months (DCR4) using RECIST and PCWG3 criteria, objective response rate, CTC0 and CTC conversion, PSA50 and ALP reductions. Additionally, T cell receptor sequencing is conducted to characterize treatment-induced changes in T cell fraction and clonal expansions, as a means of generating meaningful supportive data on the immune mechanism of PT-112 monotherapy. A Fleming two-stage design will be used to assess each arm, with a 20% DCR4 as the null hypotheses, requiring ≥6 of 25 pts responding in stage one and ≥14 of 45 in total to reject the null. In addition, other efficacy measures, such as CTC responses, as well as exposure/response and exposure/safety analyses will be applied to characterize the risk/benefit ratio and select the optimal dose regimen for PT-112. As of October 11th, 2022, 38 pts have been enrolled out of a planned maximum of 135. Clinical trial information: NCT02266745 .

208 Background: In the Phase 3 PRESTO study, intensified androgen deprivation therapy (ADT) with apalutamide (APA) with or without abiraterone acetate plus prednisone (AAP), administered for a finite treatment period of 52 weeks, prolonged prostate-specific antigen progression-free survival (PSA PFS) in pts with high-risk biochemically relapsed prostate cancer (BRPC). We evaluated baseline factors associated with PSA PFS in this study. Methods: PRESTO is a randomized phase 3, open-label trial in pts with BRPC following radical prostatectomy (RP) and PSA doubling time (PSADT) ≤ 9 months (mo), without distant metastases on conventional imaging (NCT03009981). Pts were randomized 1:1:1 to receive a finite 52-week treatment course with ADT, ADT + APA, or ADT + APA + AAP, stratified by PSADT (< 3 vs 3–9 mo), with post-treatment follow-up. Baseline factors associated with PSA PFS including Gleason sum at RP (6-7, 8, ≥ 9) were analyzed in a post hoc fashion. Results: 504 pts were randomized to ADT alone (N = 167), ADT + APA (N = 168) or ADT + APA + AAP (N = 169). Baseline patient characteristics including Gleason sum at diagnosis, serum PSA and PSADT at study entry, time interval from radical prostatectomy, and receipt of prior radiation (none, adjuvant, salvage) were well balanced across the three treatment arms. At the first planned interim analysis, both experimental arms significantly prolonged PSA PFS compared to the control arm (median 24.9 mo for ADT + APA vs 20.3 mo for ADT, HR = 0.52 (95% CI: 0.35–0.77); median 26.0 mo for ADT + APA + AAP vs 20.0 mo for ADT, HR = 0.48 (95% CI: 0.32–0.71)). Across the study cohort, Gleason sum ≥ 9 at diagnosis was associated with shorter PSA PFS (median 21.9 mo for Gleason ≥ 9 vs. 31.1 mo for Gleason 8 vs. 25.2 mo for Gleason 6-7, log-rank p-value = 0.0409). In addition, within each treatment arm, a shorter observed median PSA PFS was detected for patients with Gleason ≥ 9 prostate cancer. Serum PSA and PSADT at study entry, time from prior radical prostatectomy, and prior radiation were not associated with PSA PFS in the overall study cohort or in individual study arms. Conclusions: Gleason sum ≥ 9 prostate cancer at diagnosis was associated with shorter time to PSA progression following subsequent intensified ADT administered for a finite treatment interval in BRPC. Follow-up is ongoing to integrate genomic profiling of primary prostate cancer tissue with these results and validate with longer term endpoints including metastasis-free survival. Clinical trial information: NCT03009981 .

Abstract There are few data on the quality of cancer treatment information available on social media. Here, we quantify the accuracy of cancer treatment information on social media and its potential for harm. Two cancer experts reviewed 50 of the most popular social media articles on each of the 4 most common cancers. The proportion of misinformation and potential for harm were reported for all 200 articles and their association with the number of social media engagements using a 2-sample Wilcoxon rank-sum test. All statistical tests were 2-sided. Of 200 total articles, 32.5% (n = 65) contained misinformation and 30.5% (n = 61) contained harmful information. Among articles containing misinformation, 76.9% (50 of 65) contained harmful information. The median number of engagements for articles with misinformation was greater than factual articles (median [interquartile range] = 2300 [1200-4700] vs 1600 [819-4700], P = .05). The median number of engagements for articles with harmful information was statistically significantly greater than safe articles (median [interquartile range] = 2300 [1400-4700] vs 1500 [810-4700], P = .007).

The NCCN Guidelines for Prostate Cancer address staging and risk assessment after a prostate cancer diagnosis and include management options for localized, regional, and metastatic disease. Recommendations for disease monitoring and treatment of recurrent disease are also included. The NCCN Prostate Cancer Panel meets annually to reevaluate and update their recommendations based on new clinical data and input from within NCCN Member Institutions and from external entities. This article summarizes the panel’s discussions for the 2021 update of the guidelines with regard to systemic therapy for metastatic castration-resistant prostate cancer.

5564 Background: Cabozantinib (C) may enhance response to immune checkpoint inhibitors (ICIs) by promoting an immune-permissive microenvironment and has shown encouraging activity in combination with ICIs in tumor types including RCC and HCC. C and atezolizumab (A) have shown low objective response rates as monotherapy in metastatic castration-resistant prostate cancer (mCRPC) (Smith JCO 2012; Kim JCO 2018). COSMIC-021 (NCT03170960), a multinational phase 1b study, is evaluating the combination of C + A in various solid tumors. We report results for Cohort 6 in mCRPC. Methods: Eligible patients (pts) were required to have radiographic progression in soft tissue after enzalutamide and/or abiraterone, measurable disease, and an ECOG PS of 0 or 1. Prior chemotherapy for mCSPC was permitted. Pts received C 40 mg PO QD and A 1200 mg IV Q3W. CT/MRI scans were performed Q6W for the first year and Q12W thereafter. The primary endpoint is ORR per RECIST 1.1. Other endpoints include safety, ORR per irRECIST, duration of response (DOR), PFS, and OS. Results are presented for the first 44 pts enrolled. Results: Median follow-up as of Dec 20, 2019 was 12.6 mo (range 5, 20) for the 44 mCRPC pts. Median age was 70 y (range 49, 90), 50% had ECOG PS 1, 34% had visceral metastases, and 61% had extrapelvic lymph node metastases. 27% had prior docetaxel and 52% had 2 prior novel hormonal therapies. The most common any grade treatment-related adverse events (TRAEs) were fatigue (50%), nausea (43%), decreased appetite (39%), diarrhea (39%), dysgeusia (34%), and PPE (32%). One grade 5 TRAE of dehydration was reported in a 90 y/o. Median duration of treatment was 6.3 mo. ORR per RECIST 1.1 among all 44 pts was 32% (2 CRs [4.5%] and 12 PRs [27%]); 21 (48%) pts had SD resulting in a disease control rate of 80% in all pts. One pt with PD per RECIST 1.1 had an irPR per irRECIST. ORR per RECIST 1.1 was 33% in 36 pts with high-risk disease (visceral and/or extrapelvic lymph node metastases). Median DOR for all pts with response per RECIST 1.1 was 8.3 mo (range 2.8, 9.8+). 17 (50%) of 34 pts with post-baseline PSA evaluation had a decrease in PSA. In 12 responders with post-baseline PSA evaluation, 8 (67%) had a PSA decrease ≥50%. Tumor PD-L1 expression will also be reported. Conclusions: The combination of C + A had a tolerable safety profile and demonstrated clinically meaningful activity with durable responses in men with mCRPC. Given the encouraging activity in these pts, especially in those with high-risk disease, further evaluation of C + A in men with mCRPC is being pursued. Clinical trial information: NCT03170960 .

139 Background: C may enhance response to immune checkpoint inhibitors by promoting an immune-permissive microenvironment. COSMIC-021 (NCT03170960), a multinational phase 1b study, is evaluating the combination of C with A in various solid tumors. We report interim results from Cohort 6 in mCRPC. Methods: Eligible pts were required to have radiographic progression in soft tissue after enzalutamide and/or abiraterone, measurable disease, and an ECOG PS of 0 or 1. Prior chemotherapy for mCSPC was permitted. Pts received C 40 mg PO qd and A 1200 mg IV q3w. CT/MRI scans were performed q6w for 52w and q12w thereafter. Bone scans were performed q12w. The primary endpoint is ORR per RECIST 1.1. Other endpoints include safety, ORR per irRECIST, duration of response (DOR), PFS, and OS. Results: As of Oct 2019, 44 mCRPC pts were enrolled with a median follow-up of 10.6 mo (range 3.4+, 17.9). Median age was 70 y (range 49, 90), 50% had ECOG PS 1, 34% had visceral metastases, and 61% had extrapelvic lymph node metastases. 27% of pts had prior docetaxel and 52% had ≥2 prior novel hormonal therapies. The most common any grade TEAEs were fatigue (57%), nausea (48%), decreased appetite (45%), diarrhea (39%), PPE (32%), and vomiting (32%). One Grade 5 TRAE of dehydration was reported in a 90 y/o. Median duration of treatment was 5.3 mo. The ORR per RECIST 1.1 among all pts was 32% (2 CRs [4.5%] and 12 PRs [27%]); 21 (48%) pts had SD giving a disease control rate of 80% in all pts. One pt with initial PD per RECIST 1.1 had an irPR per irRECIST. ORR per RECIST 1.1 was 33% in 36 pts with high-risk clinical features (visceral and/or extrapelvic lymph node metastases). Median DOR for all pts with response per RECIST 1.1 was 8.3 mo (range 1.38+, 9.76+). In 12 responders with at least 1 post-baseline PSA evaluation, 8 (67%) had a PSA decline ≥50%. Conclusions: The combination of C+A had a tolerable safety profile and demonstrated clinically meaningful activity with durable responses in men with mCRPC. Given the encouraging activity in these pts, especially in those with visceral and/or extra pelvic lymph node metastases, further evaluation of C+A in men with mCRPC is being pursued. Clinical trial information: NCT03170960.