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Predicting patient-specific response to adaptive therapy in metastatic castration-resistant prostate cancer using prostate-specific antigen dynamics.

ABSTRACT: Abiraterone acetate (AA) has been proven effective for metastatic castration-resistant prostate cancer (mCRPC), and it has been proposed that adaptive AA may reduce toxicity and prolong time to progression, when compared to continuous AA. We developed a simple quantitative model of prostate-specific antigen (PSA) dynamics to evaluate prostate cancer (PCa) stem cell enrichment as a plausible driver of AA treatment resistance. The model incorporated PCa stem cells, non-stem PCa cells and PSA dynamics during adaptive therapy. A leave-one-out analysis was used to calibrate and validate the model against longitudinal PSA data from 16 mCRPC patients receiving adaptive AA in a pilot clinical study. Early PSA treatment response dynamics were used to predict patient response to subsequent treatment. We extended the model to incorporate metastatic burden and also investigated the survival benefit of adding concurrent chemotherapy for patients predicted to become resistant. Model simulations demonstrated PCa stem cell self-renewal as a plausible driver of resistance to adaptive therapy. Evolutionary dynamics from individual treatment cycles combined with metastatic burden measurements predicted patient response with 81% accuracy (specificity=92%, sensitivity=50%). In those patients predicted to progress, simulations of the addition of concurrent chemotherapy suggest a benefit between 1% and 11% reduction in probability of progression when compared to adaptive AA alone. This study developed the first mCRPC patient-specific mathematical model to use early PSA treatment response dynamics to predict subsequent responses to adaptive AA, demonstrating the putative value of integrating mathematical modeling into clinical decision making.

SUBMITTER: Brady-Nicholls R

PROVIDER: S-EPMC8322456 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Monitoring therapy response in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with novel hormonal therapies, taxanes, and newly approved therapies is crucial for optimizing treatment. [68Ga]Ga-prostate-specific membrane antigen (PSMA)-11 positron emission tomography/computed tomography (PSMA PET/CT) is a promising target for managing treatment in patients with prostate cancer. PSMA is overexpressed in patients with mCRPC; understanding how expression might change in patients undergoing treatment could determine its potential for guiding clinical decisions. We examined PSMA expression in patients with CRPC and compared PET/CT response with prostate-specific antigen (PSA) variation as a prognostic factor for progression-free survival and overall survival (PFS and OS, respectively). Methods: This was a single-center, retrospective observational cohort study in patients with CRPC enrolled in the PSMA-PROSTATA registry study (EudraCT: 2015-004589-27). A first and second (if applicable) PSMA PET/CT were performed to determine PSMA expression (absence or presence). PET/CT response was assessed as responders (patients with stable disease, partial or complete response) versus nonresponders (patients with progressive disease) by comparing the first with the second PET/CT. PSA variation (increase or decrease from baseline) was assessed across the same time period. PFS was defined as the time between second PET/CT and PSA recurrence or evidence of radiologic progression. Results: Overall, 160 patients with CRPC were included in the analysis. At first PET/CT, nearly all (n = 152; 95.0%) patients had PSMA expression (classified as mCRPC), irrespective of prior systemic therapy. SUVmax was positively associated with baseline PSA levels and velocity (both P < 0.001). According to PET/CT response, median SUVmax on first PET/CT was numerically lower in nonresponders than in responders (17.5 vs. 20.4; P = 0.127). Similarly, patients with a PSA increase had significantly lower median SUVmax on first PET/CT (15.8) than did those with a PSA decrease (30.4; P = 0.018). PSA change was, on average, 146% in nonresponders and -57% in responders between first and second PET/CT (P < 0.001). Agreement between PET/CT and PSA response was 79% (k = 0.553, P < 0.001). Among the 63 patients included in PFS/OS analyses, 76.2% had a relapse and 36.5% died before 24-mo follow-up; median PFS and OS were 6.1 and 24 mo, respectively. PET/CT response, independent of PSA variation, was a significant prognostic factor for PFS. OS was not significantly different between PET/CT responders and nonresponders. Conclusion: PSMA PET/CT may be a useful imaging method predictive of treatment response in patients with mCRPC, regardless of ongoing systemic therapy. Data also suggest that response assessed by PET/CT is a potentially more significant prognostic factor than PSA for PFS. Further studies are needed to understand the potential involvement of PSMA expression on survival.

Project description:BackgroundTherapeutic cancer vaccines have shown activity in metastatic castration-resistant prostate cancer (mCRPC), and methods are being assessed to enhance their efficacy. Ipilimumab is an antagonistic monoclonal antibody that binds cytotoxic T-lymphocyte-associated protein 4, an immunomodulatory molecule expressed by activated T cells, and to CD80 on antigen-presenting cells. We aimed to assess the safety and tolerability of ipilimumab in combination with a poxviral-based vaccine targeting prostate-specific antigen (PSA) and containing transgenes for T-cell co-stimulatory molecule expression, including CD80.MethodsWe did a phase 1 dose-escalation trial, with a subsequent expansion phase, to assess the safety and tolerability of escalating doses of ipilimumab in combination with a fixed dose of the PSA-Tricom vaccine. Patients with mCRPC received 2×10(8) plaque-forming units of recombinant vaccinia PSA-Tricom subcutaneously on day 1 of cycle 1, with subsequent monthly boosts of 1×10(9) plaque-forming units, starting on day 15. Intravenous ipilimumab was given monthly starting at day 15, in doses of 1, 3, 5, and 10 mg/kg. Our primary goal was to assess the safety of the combination. This study is registered with ClinicalTrials.gov, number NCT00113984.FindingsWe completed enrolment with 30 patients (24 of whom had not been previously treated with chemotherapy) and we did not identify any dose-limiting toxic effects. Grade 1 and 2 vaccination-site reactions were the most common toxic effects: three of 30 patients had grade 1 reactions and 26 had grade 2 reactions. 21 patients had grade 2 or greater immune-related adverse events. Grade 3 or 4 immune-related adverse events included diarrhoea or colitis in four patients and grade 3 rash (two patients), grade 3 raised aminotransferases (two patients), grade 3 endocrine immune-related adverse events (two patients), and grade 4 neutropenia (one patient). Only one of the six patients previously treated with chemotherapy had a PSA decline from baseline. Of the 24 patients who were chemotherapy-naive, 14 (58%) had PSA declines from baseline, of which six were greater than 50%.InterpretationThe use of a vaccine targeting PSA that also enhances co-stimulation of the immune system did not seem to exacerbate the immune-related adverse events associated with ipilimumab. Randomised trials are needed to further assess clinical outcomes of the combination of ipilimumab and vaccine in mCRPC.FundingUS National Institutes of Health.

Project description:BackgroundProstate-specific membrane antigen (PSMA)-targeted radionuclide therapy (TRT) has demonstrated efficacy and tolerability with a dose-response effect in phase I/II trials in men with metastatic castration-resistant prostate cancer (mCRPC). The need for positive PSMA imaging before PSMA-TRT to select patients is largely practiced, but its utility is not proven. Given target heterogeneity, developing a biomarker to identify the optimal patient population remains an unmet need. The aim of this study was to assess PSMA uptake by imaging and response to PSMA-TRT.MethodsWe performed an analysis of men with mCRPC enrolled in sequential prospective phase I/II trials of PSMA-TRT. Each patient had baseline PSMA imaging by planar 111 In and/or 177 Lu SPECT (N = 171) or 68 Ga-PSMA-11 PET/CT (N = 44), but the results were not used to include/exclude treatment. Semiquantitative imaging scores (IS) on a 0-4 scale were assigned based on PSMA uptake in tumors compared to liver uptake. We compared the ≥50% PSA decline response proportions between low (0-1) and high (2-4) PSMA IS using the χ2 -test. We used multivariable logistic regression analysis to understand the relationship between independent and dependent variables, including IS, radionuclide activity (dose) administered, CALGB (Halabi) prognostic risk score, prior taxane use.Results215 men with progressive mCRPC received PSMA-TRT as follows: 177 Lu-J591 (n = 137), 177 Lu-PSMA-617 (n = 44), 90 Y-J591 (n = 28), 177 Lu-J591 + 177 Lu-PSMA-617 (n = 6). High PSMA expression (IS 2-4) was found in 160 (74.4%) patients and was significantly associated with more frequent ≥ 50% PSA reduction (26.2 vs. 7.3%, p = .006). On multivariate logistic regression analysis, higher IS was associated with a ≥50% decrease in PSA, even after accounting for CALGB (Halabi) prognostic score, the dose administered, and previous taxane use (OR, 4.72; 95% CI, 1.71-16.85; p = .006). Patients with low PSMA expression (N = 55, 24.7%) were less likely to respond. Thirteen of 26 (50%) with no PSMA uptake (IS = 0) had post-PSMA-TRT PSA decline with 2 (7.7%) having ≥ 50% PSA declines.ConclusionCollectively, the data provide evidence in favor of the hypothesis that patients with high PSMA uptake and high administered radionuclide dose correlate with a higher chance of response.

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Predicting patient-specific response to adaptive therapy in metastatic castration-resistant prostate cancer using prostate-specific antigen dynamics.

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