Dendritic cell vaccine (DCVAC) combined with chemotherapy (CMT) in patients with newly diagnosed epithelial ovarian carcinoma (EOC) after primary debulking surgery (PDS): Biomarker exploratory analysis of a phase 2, open-label, randomized, multicenter trial.
Authors: Rob Lukas , Cibula David , Knapp Pawel , Mallmann Peter , Klat Jaroslav , Minar Lubos , Bartos Pavel , Chovanec Josef , Valha Petr , Pluta Marek , Novotny Zdenek , Spacek Jiri , Melichar Bohuslav , Kieszko Dariusz , Fucikova Jitka , Hrnciarova Tereza , Korolkiewicz Roman Pawel , Hraska Marek , Bartunkova Jirina , Spisek Radek 
Published: June 2021

5521 Background: Most patients with EOC relapse despite PDS and CMT. Autologous DCVAC can present tumor antigens to elicit a durable immune response. We hypothesized that adding DCVAC to CMT stimulates antitumor immunity and improves clinical outcomes. Methods: Key eligibility criteria were FIGO stage III EOC (serous, endometrioid, or mucinous), post-PDS with < 1 cm maximal residuum, no prior systemic therapy, and ECOG 0-2. In part 1, patients were randomized up to 6 weeks after PDS, 1:1:1, into arm A (A; DCVAC concomitant with CMT), arm B (B; DCVAC sequential after CMT), and arm C (C; CMT). Patients were stratified by tumor residuum (0 or < 1 cm). CMT consisted of 6 cycles of carboplatin (AUC 5-7) and paclitaxel (175 mg/m2). Patients in A and B received up to 10 doses of DCVAC (1×107 DCs/dose). The primary endpoint was radiologically assessed progression-free survival (PFS). The key secondary endpoint was overall survival (OS). Results presented refer to a protocol-defined modified intention-to-treat population (mITT) including patients who received ≥1 CMT dose in C or ≥1 DCVAC dose in A and B. Results: Between November 2013 and March 2016, 99 patients were randomized. At the final analysis, the mITT included 31 patients in A, 29 patients in B, and 30 patients in C. Key baseline characteristics and DCVAC exposure were comparable across treatment arms. Median PFS was 20.3 months in A, not reached in B, and 21.4 months in C, with corresponding HRs (95% CI) compared to C of 0.98 (0.48-2.00) in A and 0.39 (0.16-0.96) in B. The PFS benefit in B was statistically significant (p = 0.034) This was supported by a non-significant trend in OS in A and B. Median OS was not reached in any arm at the time of median follow-up of 66 months (34% of events). Patients with low CD8+ T-cell counts (CD8Lo) in tumor samples in A and B had significantly improved clinical outcomes compared to patients in C with CD8Lo: median PFS gain of 6 months (19 vs 13 months) and a more robust OS gain (median not reached vs 31 months), with minimal difference between A and B. This effect could not be attributed to statistical differences in high CD8+ T-cell counts (CD8Hi) density patients. These findings indicated the best clinical outcome in DCVAC patients with immunologically “cold” tumors in both DCVAC arms. DCVAC showed a good safety profile with only 8 DCVAC-related adverse events (Grade 1-2). Conclusions: DCVAC improved PFS and OS outcomes in patients with newly diagnosed EOC, predominantly in patients with immunologically “cold” tumors, thus representing a promising treatment option in this patient population. Clinical trial information: NCT02107937.