AdoRN Trial: Atezolizumab in combination with neoadjuvant chemotherapy and interval cytoreductive surgery for patients with newly-diagnosed advanced-stage epithelial ovarian cancer

Abstract

<h3>Objectives:</h3> To determine safety, efficacy, and biomarkers of response to neoadjuvant therapy (NACT) with atezolizumab (atezo), weekly paclitaxel and carboplatin (wPC) followed by maintenance (maint) atezo±bevacizumab (bev) in women with advanced epithelial ovarian, tubal, and peritoneal cancer (EOC). <h3>Methods:</h3> Patients (pts) with high-grade EOC were eligible. Pts underwent pretreatment biopsy, received paclitaxel 80 mg/m² IV D1/8/15 + carboplatin AUC6 IV D1 + atezo 1200 mg D1 every 3 weeks x 3 cycles followed by interval cytoreductive surgery (ICS). Post-surgery, pts received adjuvant atezo, wPC±bev followed by maint atezo±bev. Primary objective was to assess safety of the combination when given prior to ICS. Early stopping rules were built around the primary safety endpoint if patients were unable to proceed to planned ICS within the specified timeframe (≤6 weeks from last dose of NACT) due to atezo-related toxicities. Safety was assessed in all treated pts using frequency and severity of adverse events (AE). Objective response rate (ORR), pathologic complete response rate (pCR) at ICS, and progression free survival (PFS) were determined. Planned exploratory objectives included quantitation of changes in PD-L1 expression, tumor-infiltrating lymphocyte subpopulations, immune checkpoint receptor profile, and immune blood-based markers. <h3>Results:</h3> A total of 18 pts enrolled and received therapy between 05/15/2018 - 07/14/2020. Median age was 69 years (range 46-87). Key disease characteristics: 18 (100%) pts had high-grade serous EOC; 13 (72%) pts had Stage III and 5 (28%) had stage IV disease; <i>BRCA</i> status: 5 (28%) mutations, 13 (72%) wildtype. Grade (G) 3/4 atezo-related AEs included 1 (6%) G3 anemia, 2 (11%) G3 thrombocytopenia, 2 (11%) G4 hypokalemia, 2 (11%) G3 rash, 1 (6%) thrombotic event. Other AEs of special interest included pneumonitis (n=3, 2 G2, 1 G1), blurred vision (n=1, G1), and myositis (n=1, G1). A total of 3 pts withdrew prior to ICS; 1 to change to every 3 weeks therapy locally, 1 due to non-atezo related AEs, and 1 due to negative results of IMAGYN050. These 3 pts are not included in the response-evaluable population (n=15). Nine (60%) pts had a partial response (PR) after 3 cycles and 6 (40%) had stable disease. All 15 pts underwent ICS; 1 had delayed cytoreduction due to pulmonary embolism, possibly atezo-related. Cytoreduction status was optimal in 86% pts [R0 8 (53%), R1 (33%)], and suboptimal in 2 (13%) pts; no pCRs were observed. All response-evaluable pts completed chemotherapy. Pts opted for maint therapy as follows: 6 (40%) adjuvant/maint atezo+bev; 4 (27%) atezo alone; and 5 (33%) withdrew for PARP inhibitor maint. A total of 2 (20%) of 10 receiving atezo maint discontinued due to recurrence. Blood-based and tumor biomarker results will be presented. <h3>Conclusions:</h3> NACT with atezo + wPC followed by maint atezo±bev was feasible with no new safety signals. Biomarker analysis is ongoing to identify potential candidates who may benefit from atezo front-line therapy.