Wen, Yujia

8057 Background: The NCI Adjuvant Lung Cancer Enrichment Marker Identification and Sequencing Trials (ALCHEMIST) study tested resected stage II-IIIB(N2) NSCLC for targetable EGFR and ALK alterations and PD-L1 expression to screen patients for biomarker-driven adjuvant therapy trials (NCT02194738). Local lab results were requested when available for comparison to central lab results. Methods: We identified patients with both central and local PD-L1 results in the ALCHEMIST adjuvant immunotherapy study screening population. Discrepancies in tumor proportion score (TPS) between central and local PD-L1 were defined using prespecified cut-points (granular: <1%, 1-<5%, 5-<10%, 10-<20%, 20-<30%, 30-<40%, 40-<50%, 50-60%, 60-<70%, 70-<80%, 80-<90%, 90-<100%; clinical: <1%, 1-<50%, 50-100%). Large discrepancies were defined as ≥ 50 percentage point differences; for these cases, local PD-L1 and hematoxylin & eosin-stained slides were requested. These and all central slides were digitally scanned at 40X. Three expert pathologists reviewed the scanned slides in a blinded fashion. Differences between patient or tumor characteristics were assessed by Chi-square and Wilcoxon rank sum tests. Percent agreement was computed within and between the reviewers. Results: Central and local PD-L1 results were available for 497 patients. 177 cases (36%) had discrepancies that placed patients in different clinical TPS categories (<1%, 1-<50%, 50-100%). Among these, 43 cases had large TPS discrepancies; 14 had available local testing slides. 46 of the 320 cases without discrepancy were randomly selected as controls. No patient or tumor characteristics were associated with discrepancy, including tumor location, histology, grade or cancer stage (p > 0.05). Pairwise comparisons of TPS according to three pathologists re-reading the same scanned PD-L1 slides showed similar levels of disagreement in clinical TPS category whether there was initial discrepancy between central and local results (24%, 34%, and 23%; mean 27%) or not (33%, 30%, and 20%; mean 28%). Among the 14 cases with large initial discrepancies and local slides available, there was agreement in clinical TPS category when the anonymized central and local scanned slides were re-read by the pathologists in 54%, 38%, and 43% of cases, despite 100% non-agreement in initial reads. There were higher rates of agreement when the tested slides both originated from the same (100%) versus different (35%) blocks, when the same (48%) versus different (40%) PD-L1 antibodies were used, and when the cases were of non-squamous (52%) versus squamous (14%) cell carcinoma. Conclusions: There are substantial differences in PD-L1 TPS read by pathologists that can result in placement of patients in different categories commonly used for clinical management. These differences have clear implications in clinical trials and routine patient care.

4514 Background: Maintenance avelumab is a standard of care in patients (pts) with la/mUC who do not progress after first-line PBC. Cabozantinib (CABO) is an oral inhibitor of MET, VEGFR and TAM, active in multiple solid tumors. We hypothesized that an avelumab (Av)-CABO combination would improve outcomes in pts with mUC with an acceptable safety profile compared to avelumab maintenance alone. Methods: MAIN-CAV (NCT05092958) is a phase III randomized, multicenter, international trial for la/mUC pts who did not progress after 4-6 cycles of any PBC (gemcitabine-cisplatin, gemcitabine-carboplatin, MVAC, ddMVAC). Pts were randomized 1:1 to Av 800 mg IV every 2 weeks alone or with CABO 40 mg daily for ≤2 years. Stratification factors were response to first-line PBC (complete response [CR] vs partial response [PR] vs stable disease [SD]) and visceral metastases. The primary endpoint was overall survival (OS); secondary endpoints included progression-free survival (PFS), safety and quality of life. The target accrual was 654 pts; the trial closed early after enrollment of 68 pts following adoption of enfortumab vedotin plus pembrolizumab as the new preferred first-line standard in the US. Results: From 3/2022 to 3/2024, 68 pts were randomized (Av n = 33; CABO-Av n = 35). Median OS was 24.8 months (mo) with Av and 23.0 mo with Avb-CABO (Hazard ratio 1.41; 95% CI 0.66–3.01; p = 0.186). Median PFS was 4.6 mo with Av vs 6.0 mo with Av-CABO (p = 0.343). Objective response rate among pts with PR or SD after first-line PBC was 20.8% with Av vs 11.5% with Av-CABO (p = 0.424). Grade ≥3 treatment-related adverse events occurred in 24.2% pts on the Av arm vs 39.4% of pts on the Av-CABO arm and CABO dose reductions occurred in 63% of pts. Conclusions: Addition of CABO to Av did not improve OS or PFS compared with Av alone in this underpowered, prematurely closed phase III trial; safety was consistent with known profiles. U10CA180821,U10CA180882; U24CA196171, U10CA180863. (CCTG);U10CA180888 (SWOG); https://acknowledgments.alliancefound.org. Clinical trial information: NCT05092958 .

Abstract Background Reference sets are needed to evaluate performance of multi-cancer detection (MCD) assays. The National Cancer Institute funded the Alliance reference set study to assess MCDs for use in future trials. Methods Individuals with cancer and controls were recruited; blood specimens were collected prior to cancer treatment. A performance evaluation study was designed utilizing reference set samples. Companies (n = 6) were selected to participate based on review of performance data and ability to utilize the blood collection tube. Companies received samples from cancer types their assay was designed to detect (“targeted”), plus additional “non-targeted” and control samples. Companies reported positive/negative calls, risk scores, and tissue-of-origin (TOO) predictions. Sensitivity was computed for early (I-II) and late (III-IV) stage cases, based on positive/negative calls (SEPN) and at fixed 98% specificity (SE98). Specificity and TOO accuracy were computed. Results Five hundred and forty nine cases (encompassing 13 cancer types) and 413 controls from the reference set were included in the study. Companies assessed samples from median 6 (range 5-9) targeted cancer types and median 8 (range: 7-11) overall cancer types. Median (range) specificity was 92.3% (76.5%-98.5%). Median (range) SEPN was 32% (25%-42%) for early stage and 73% (48%-89%) for late stage; while median (range) SE98 was 19% (8%-35%) for early stage and 66% (13%-79%) for late stage. Median sensitivity for non-targeted types was 40% (early stage) and 52% (late stage). Median (range) TOO accuracy (primary predicted site) was 75% (64%-78%). Conclusions Sensitivity and specificity varied widely across assays with early-stage sensitivity substantially lower than late-stage sensitivity. Clinical Trial Registration Number ClinicalTrials.gov identifier NCT05334069.

Abstract Sorafenib blocks nonstructural protein 5A (NS5A)-recruited c-Raf–mediated hepatitis C virus (HCV) replication and gene expression. Release of Raf-1-Ask-1 dimer and inhibition of Raf-1 via sorafenib putatively differ in the presence or absence of doxorubicin. Cancer and Leukemia Group B (CALGB) 80802 (Alliance) randomized phase III trial of doxorubicin plus sorafenib versus sorafenib in patients with advanced hepatocellular carcinoma (HCC), showed no improvement in median overall survival (OS). Whether HCV viral load impacts therapy and whether any correlation between HCV titers and outcome based on HCV was studied. In patients with HCV, HCV titer levels were evaluated at baseline and at multiple postbaseline timepoints until disease progression or treatment discontinuation. HCV titer levels were evaluated in relation to OS and progression-free survival (PFS). Among 53 patients with baseline HCV data, 12 patients had undetectable HCV (HCV-UN). Postbaseline HCV titer levels did not significantly differ between treatment arms. One patient in each arm went from detectable to HCV-UN with greater than 2 log-fold titer levels reduction. Aside from these 2 HCV-UN patients, HCV titers remained stable on treatment. Patients who had HCV-UN at baseline were 3.5 times more likely to progress and/or die from HCC compared with HCV detectable (HR = 3.51; 95% confidence interval: 1.58–7.78; P = 0.002). HCV titer levels remained unchanged, negating any sorafenib impact onto HCV titer levels. Although an overall negative phase III study, patients treated with doxorubicin plus sorafenib and sorafenib only, on CALGB 80802 had worse PFS if HCV-UN. Higher levels of HCV titers at baseline were associated with significantly improved PFS. Significance: Sorafenib therapy for HCC may impact HCV replication and viral gene expression. In HCV-positive patients accrued to CLAGB 80802 phase III study evaluating the addition of doxorubicin to sorafenib, HCV titer levels were evaluated at baseline and different timepoints. Sorafenib did not impact HCV titer levels. Despite an improved PFS in patients with detectable higher level HCV titers at baseline, no difference in OS was noted.

TPS714 Background: 1st-line induction platinum-based chemotherapy followed by switch maintenance Av is the current preferred standard of care in patients (pts) with aUC who do not progress after platinum-based chemotherapy. There is an significant need to further improve outcomes by combining Av with an effective, non-cross resistant therapy with non-overlapping toxicity. CABO is an oral inhibitor of MET, VEGFR and TAM family receptors involved in tumor growth, angiogenesis and immune cell regulation and has shown efficacy in UC in combination with PD-1/PD-1L1 inhibitor. We hypothesized that CABO-Av combination would improve survival vs Av alone and have an acceptable safety profile as switch maintenance therapy in mUC. Methods: MAIN-CAV is a phase III randomized, multicenter, international trial for pts with locally advanced/metastatic UC (including cN3M0 only)) who do not progress after 4-6 cycles of any platinum-based chemotherapy (gem-cis, gem-carbo, MVAC or ddMVAC). 654 adults are randomized 1:1 within 3-10 weeks (wk) after last dose of chemotherapy to receive Av 800 mg IV every 2 wk or Av and CABO 40 mg daily for up to 2 yrs. Key eligibility criteria include ECOG PS 0-1, no prior use of anti-PD(L)1, no CNS metastases, no major surgery within 4 wks, no uncontrolled hypertension or cardiovascular disorders. Pts are stratified based on 1) best response to 1L chemotherapy: complete vs partial response vs stable disease and 2) presence vs absence of visceral metastases. The primary endpoint is overall survival (OS) with assumptions of 1-sided alpha 0.025, power 80%, median OS 21 months (mo) with Av and hazard ratio 0.75, thus hypothesizing median OS 28 mo on CABO-Av. Key secondary endpoints include progression-free survival, safety, tolerability, and efficacy of CABO-Av vs Av alone based on RECIST 1.1 and iRECIST criteria (and PD-L1 status).Quality of life (QOL) are assessed using EQ-5D-5L, PROMIS-Fatigue 4a, EORTC QLQ-C30, EORTC QLQ-BLM30 between pts on CABO-Av vs Av alone. Biomarkers of response and resistance to Av will be assessed using baseline archival tissues, baseline and serial blood, ctDNA, stool and urine. Imaging studies will test the correlation of established and new radiomic signatures with survival, adverse events and QOL and incorporate both radiologic and biologic features to assess their potential association with outcomes. This trial would be the first to systematically address whether adding the multitargeted TKI, CABO, to Av improves survival vs Av alone as 1L maintenance therapy. https://acknowledgments.alliancefound.org . Support: U10CA180821, U10CA180882; U24CA196171, U10CA180863 (CCTG); Clinical trial information: NCT05092958 .

TPS277 Background: Despite a growing number of treatment options for first-line mCRPC, approximately 40% of patients (pts) have radiographic progression within the first year. Co-inhibition of androgen receptor (AR) and PARP is a promising therapeutic strategy that leverages synthetic lethality induced by impaired double-strand DNA repair. Two phase III studies have shown improvement in radiographic progression-free survival (rPFS) in HRR-mutant pts with abiraterone + PARPi combinations vs abiraterone alone. However, the results in HRR-wild type pts are conflicting, with only one of the studies demonstrating a benefit with the abiraterone + PARPi combination. ENZ + RUCA has shown an acceptable safety profile & no significant drug-drug interactions (S-DDI) in a phase 1b trial. This allows its evaluation in mCRPC. Methods: CASPAR (A031902) is a phase 3 study in which 984 pts will be randomized on a 1:1 basis to ENZ plus RUCA/PBO. HRR gene aberration is not required for enrollment. All pts will undergo next-generation targeted exome sequencing from archival tumor tissue (new biopsy only required if no archival tissue is available). Treatment will be continued until disease progression and crossover is not allowed. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-2, biopsy-proven prostate adenocarcinoma, progressive (PSA or radiographic) disease per Prostate Cancer Working Group 3 guidelines, measurable or non-measurable disease per RECIST 1.1, no prior treatment for mCRPC (prior docetaxel, abiraterone, darolutamide, or apalutamide in non-mCRPC setting is allowed), no significant uncontrolled comorbidity, and no medications with S-DDI with ENZ/RUCA. Hierarchical co-primary endpoints are overall survival (OS) and rPFS. The OS analysis will be undertaken as a primary endpoint if the rPFS endpoint is met. For a one-sided logrank test with a type 1 error rate equal to 0.025, the study has 90% power to detect a hazard ratio (HR) of 0.71 in rPFS (median rPFS of 15 and 21 months in control and combination arms, respectively), and 80% power to detect an HR of 0.80 in OS (median OS of 32 and 40 months, respectively). Key secondary endpoints are rPFS and OS in pts with vs without pathogenic BRCA1, BRCA2, or PALB2 alterations; and differences in adverse events and quality of life (QOL) outcomes between the treatment arms. QOL assessments include Functional Assessment of Cancer Therapy–Prostate (FACT-P), Brief Pain Inventory Short Form (BPI-SF), and EQ-5D-5L. A key correlative endpoint is the sensitivity of ctDNA testing for HRR gene alterations. Enrollment began in July 2021 & the study is available for participation to all US-NCTN sites. Clinical trial information: NCT04455750 .

TPS5107 Background: Despite a growing number of treatment options for first line mCRPC, approximately 40% of patients (pts) have radiographic progression within the first year. Androgen receptor (AR) signaling inhibition increases genomic instability with double-strand DNA breaks & co-inhibition of AR & PARP induces synthetic lethality in multiple preclinical models. Homologous recombination repair (HRR) gene aberrations do not appear to be necessary for this synergy as demonstrated in a ph 3 clinical trial of abiraterone & olaparib where this combination improved radiographic progression-free survival (rPFS) in HRR-wild-type pts compared with abiraterone alone. A ph 1b trial has since shown that enzalutamide plus rucaparib has acceptable safety profile & no significant drug-drug interactions (S-DDI). Methods: CASPAR/A031902 (NCT04455750) is a ph 3 study in which 984 pts will be randomized 1:1 to enzalutamide plus rucaparib or placebo. HRR gene aberration is not required for enrollment. All pts will undergo next-generation targeted-exome sequencing from archival tumor tissue (new biopsy only required if no archival tissue available). Treatment will be continued until disease progression & crossover is not allowed. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-2, biopsy-proven prostate adenocarcinoma, progressive (PSA or radiographic) disease per Prostate Cancer Working Group 3 guidelines, measurable or nonmeasurable disease per RECIST 1.1, no prior treatment for mCRPC (prior docetaxel, abiraterone, darolutamide, or apalutamide in non-mCRPC setting is allowed), no significant uncontrolled comorbidity, & no medications with S-DDI with enzalutamide/rucaparib. Hierarchical co-primary endpoints are rPFS & overall survival (OS). The OS analysis will be undertaken as a primary endpoint if the rPFS endpoint is met. For a one-sided logrank test with a type 1 error rate equal to 0.025, the study has 90% power to detect a hazard ratio (HR) of 0.71 in rPFS (median rPFS of 15 & 21 months in control & combination arms, respectively) & 80% power to detect an HR of 0.80 in OS (median OS of 32 & 40 months, respectively). Key secondary endpoints are rPFS & OS in pts with vs without pathogenic BRCA1, BRCA2, or PALB2 alterations; & differences in adverse events & quality of life (QOL) outcomes between the treatment arms. QOL assessments include Functional Assessment of Cancer Therapy–Prostate (FACT-P), Brief Pain Inventory Short Form (BPI-SF) & EQ-5D-5L. A key correlative endpoint is the sensitivity of ctDNA-based testing for alterations in HRR genes. Enrollment to CASPAR began in July 2021 & the study is available for participation to all US-NCTN sites with a projected enrollment of 3 years. Support: U10CA180821, U10CA180882, U24CA196171; U10CA180888. Clinical trial information: NCT04455750.

TPS194 Background: Despite a growing number of treatment options for first line mCRPC, approximately 40% of patients (pts) have radiographic progression within the first year. Androgen receptor (AR) signaling inhibition increases genomic instability with double-strand DNA breaks & co-inhibition of AR & PARP induces synthetic lethality in multiple preclinical models. Homologous recombination repair (HRR) gene aberrations do not appear to be necessary for this synergy as demonstrated in a ph 2 clinical trial of abiraterone & olaparib where this combination improved radiographic progression-free survival (rPFS) in HRR-wild-type pts compared with abiraterone alone. A ph 1b trial has since shown that enzalutamide plus rucaparib has acceptable safety profile & no significant drug-drug interactions (S-DDI). Methods: CASPAR/A031902 (NCT04455750) is a ph 3 study in which 984 pts will be randomized 1:1 to enzalutamide plus rucaparib or placebo. HRR gene aberration is not required for enrollment. All pts will undergo next-generation targeted-exome sequencing from archival tumor tissue (new biopsy only required if no archival tissue available). Treatment will be continued until disease progression & crossover is not allowed. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-2, biopsy-proven prostate adenocarcinoma, progressive (PSA or radiographic) disease per Prostate Cancer Working Group 3 guidelines, measurable or nonmeasurable disease per RECIST 1.1, no prior treatment for mCRPC (prior docetaxel, abiraterone, darolutamide, or apalutamide in non-mCRPC setting is allowed), no significant uncontrolled comorbidity, & no medications with S-DDI with enzalutamide/rucaparib. Hierarchical co-primary endpoints are rPFS & overall survival (OS). The OS analysis will be undertaken as a primary endpoint if the rPFS endpoint is met. For a one-sided logrank test with a type 1 error rate equal to 0.025, the study has 90% power to detect a hazard ratio (HR) of 0.71 in rPFS (median rPFS of 15 & 21 months in control & combination arms, respectively) & 80% power to detect an HR of 0.80 in OS (median OS of 32 & 40 months, respectively). Key secondary endpoints are rPFS & OS in pts with vs without pathogenic BRCA1, BRCA2, or PALB2 alterations; & differences in adverse events & quality of life (QOL) outcomes between the treatment arms. QOL assessments include Functional Assessment of Cancer Therapy–Prostate (FACT-P), Brief Pain Inventory Short Form (BPI-SF) & EQ-5D-5L. A key correlative endpoint is the sensitivity of ctDNA-based testing for alterations in HRR genes. Enrollment to CASPAR began in July 2021 & the study is available for participation to all US-NCTN sites with a projected enrollment of 3 years. Support: U10CA180821, U10CA180882, U24CA196171; U10CA180888; Clovis Oncology; http://acknowledgments.alliancefound.org Clinical trial information: NCT04455750.