Kessel, Adam

Abstract Background Vorasidenib is Food and Drug Administration‐approved for treatment of grade 2 isocitrate dehydrogenase (IDH)–mutant gliomas and has demonstrated a benefit in progression‐free survival compared to a placebo. This study assessed the cost‐effectiveness of this treatment strategy compared to standard treatment: observation or chemoradiation (CRT). Methods The authors used an integrated Markov model to compare quality‐adjusted life‐years (QALY) gained and cost‐effectiveness of patients with IDH‐mutated low‐grade glioma (LGG) treated with vorasidenib, observation, or CRT. Outcomes were expressed as incremental cost‐effectiveness ratios (ICERs) per QALY gained. Treatment is considered cost‐effective if it meets the commonly accepted willingness‐to‐pay threshold of $100,000 per QALY gained. Results Based on model parameters, vorasidenib demonstrated an ICER of $356,756 per QALY when compared to CRT. When compared to observation, vorasidenib demonstrated an improved ICER of $215,191 per QALY. On one‐way sensitivity analysis compared to observation, median cost of vorasidenib and median overall survival were most likely to affect ICER with only marginal changes on analysis of other model factors. For ICER to become ≤$100,000 compared to observation, the cost of vorasidenib would need to drop to below $14,072 monthly or have a median survival gain of at least 11.9 years. The probabilistic sensitivity analysis demonstrated that vorasidenib was favored in none of 5000 Monte Carlo iterations. Conclusion Using the best available data, the current price of vorasidenib does not meet commonly accepted cost‐effectiveness thresholds in treatment of IDH‐mutated LGGs.

129 Background: Few studies have explored the use of focal therapies to address select sites of resistant disease in men receiving 177-Lu-PSMA-617 for metastatic castrate resistant prostate cancer (mCRPC). Our institutional practice is to offer SBRT for patients with up to 5 sites of oligoprogression or non-responding lesions while undergoing 177Lu-PSMA-617 (every 6 weeks for 6 cycles total). This is determined by PSMA or choline PET imaging during the course of 177Lu-PSMA-617. Herein, we evaluated the safety of adding target SBRT during treatment with 177Lu-PSMA-617. Methods: This retrospective single institution analysis was conducted via systematic chart review to evaluate for adverse events during or after treatment. Grading of treatment-related adverse events was conducted using Common Terminology Criteria for Adverse Events Version 5.0 (CTCAE v5). Results: Thirty-one patients receiving 177Lu-PSMA-617 with 51 sites of oligoprogressive or non-responding metastatic disease were treated with SBRT. The median number of sites treated was 1 (range 1-4). Most patients received SBRT immediately after cycle 6 (32%) or after cycle 3 or 4 (42%). Bone was the most commonly treated site of disease (90%) with the majority (54%) of bone sites being spine or sacrum, followed by lymph nodes (10%). Ultimately, 84% of patients completed all 6 cycles of 177Lu-PSMA-617 (range 4-6). The median follow-up time was 19.1 months (IQR 15.5-22.4) after 177Lu-PSMA-617 therapy start. A total of 2 patients experienced a pathologic fracture within the SBRT treatment field that could possibly be related to radiotherapy. One patient experienced a grade 2 neuropathy which may have been related to radiation therapy. Other potential adverse events are listed (Table). Conclusions: Our data demonstrates a low rate of significant toxicity with the use SBRT during treatment with 177Lu-PSMA-617. Further study is indicated to determine the oncologic efficacy and potential late side effects of this treatment strategy. Adverse events. Event All Grades Grade > 3 Any Adverse Event 104 2 Anemia 29 (94%) 0 Low Platelets 11 (35.5%) 1 (3.2%) Any Pathologic Fracture 7 (22.5%) 1 (3.2%) Possible SBRT-related Pathologic Fracture 2 (6.5%) 1 (3.2%) Bone Pain Flare 3 (9.6%) 0 Neuropathy 1 (3.2%) 0

PURPOSE Two poly (ADP-ribose) polymerase (PARP) inhibitors (olaparib and rucaparib) are US Food and Drug Administration–approved for patients with metastatic castration-resistant prostate cancer (mCRPC) harboring BRCA1/ 2 mutations, but the relative efficacy of PARP inhibition in BRCA1- versus BRCA2-altered mCRPC is understudied. METHODS We conducted a multicenter retrospective analysis involving 12 sites. We collected genomic and clinical data from 123 patients with BRCA1/ 2-altered mCRPC who were treated with PARP inhibitors. The primary efficacy end point was the prostate-specific antigen (PSA) response (≥ 50% PSA decline) rate. Secondary end points were PSA progression-free survival (PSA-PFS), clinical or radiographic PFS, and overall survival. We compared clinical outcomes, and other genomic characteristics, among BRCA1- versus BRCA2-altered mCRPC. RESULTS A total of 123 patients (13 BRCA1 and 110 BRCA2) were included. PARP inhibitors used were olaparib (n = 116), rucaparib (n = 3), talazoparib (n = 2), and veliparib (n = 2). At diagnosis, 72% of patients had Gleason 8-10 disease. BRCA1 patients were more likely to have metastatic disease at presentation (69% v 37%; P = .04). Age, baseline PSA, metastatic distribution, and types of previous systemic therapies were similar between groups. There were equal proportions of germline mutations (51% v 46%; P = .78) in both groups. BRCA1 patients had more monoallelic (56% v 41%; P = .49) and concurrent TP53 (55% v 36%; P = .32) mutations. PSA 50 responses in BRCA1- versus BRCA2-altered patients were 23% versus 63%, respectively ( P = .01). BRCA2 patients achieved longer PSA-PFS (HR, 1.94; 95% CI, 0.92 to 4.09; P = .08), PFS (HR, 2.08; 95% CI, 0.99 to 4.40; P = .05), and overall survival (HR, 3.01; 95% CI, 1.32 to 6.83; P = .008). Biallelic (compared with monoallelic) mutations, truncating (compared with missense) mutations, and absence of a concurrent TP53 mutation were associated with PARP inhibitor sensitivity. CONCLUSION PARP inhibitor efficacy is diminished in BRCA1- versus BRCA2-altered mCRPC. This is not due to an imbalance in germline mutations but might be related to more monoallelic mutations and/or concurrent TP53 alterations in the BRCA1 group.

100 Background: Two PARP inhibitors (olaparib, rucaparib) are now FDA approved for mCRPC patients with mutations in BRCA1/2, but the relative efficacy of PARP inhibition in BRCA1- vs BRCA2-altered mCRPC is understudied. Methods: We conducted a multi-center retrospective analysis involving 11 academic sites. We collected genomic and clinical data from 123 BRCA1/2-altered mCRPC patients receiving PARP inhibitor treatment. The primary efficacy endpoint was PSA50 response rate (≥50% decline in PSA level). Secondary endpoints were PFS (clinical, radiographic or PSA progression, whichever occurred first) and overall survival (OS). We also captured information on other concurrent genomic alterations. We compared genomic characteristics and clinical outcomes among BRCA1- vs BRCA2-altered mCRPC. Results: A total of 123 patients (13 BRCA1, 110 BRCA2) were included. PARP inhibitors used were olaparib (n = 116), rucaparib (n = 3), talazoparib (n = 2) and veliparib (n = 2). All BRCA1 and 71% of BRCA2 patients had Gleason 8-10 disease. Compared to BRCA2 patients, BRCA1 patients were more likely to have received prior taxane chemotherapy (77% vs 62%). Age, baseline PSA, and prior enzalutamide/abiraterone treatment were similar between groups. PSA50 responses in BRCA1- vs BRCA2-altered patients were 38% vs 65% respectively ( P= 0.06). Median PFS in BRCA1 vs BRCA2 patients was 3.0 mo (95%CI, 0.9–5.1) vs 8.0 mo (95%CI, 5.3–10.6) respectively (HR 0.42, P= 0.01). Similarly, median OS in BRCA1 vs BRCA2 patients was 11.0 mo (95%CI, 9.9–12.1) vs 24.0 mo (95%CI, 18.2–29.8) respectively (HR 0.33, P= 0.005). There were roughly equal proportions of germline mutations (50% vs 45%) and biallelic mutations (31% vs 25%) in the BRCA2 and BRCA1 groups, respectively. There were numerically more TP53 mutations in the BRCA1 vs BRCA2 group (40% vs 29%, P= 0.45), but an equal number of mutations in other key genes ( PTEN, RB1 and AR). Conclusions: PARP inhibitor activity is diminished in BRCA1- vs BRCA2-altered mCRPC. In our cohort, this differential activity was not explained by mutation origin (germline vs somatic) or allelic status (mono- vs biallelic). These findings warrant validation.