Study design, endpoints, and statistical analysis
toxicity, toxicities, death
ADVERSE EVENTS, ADVERSE EVENT, DISEASE PROGRESSION
The primary endpoint was the incidence of dose-limiting toxicities (DLT) within 11 weeks after the initiation of treatment, corresponding to the first six cycles of nivolumab. DLT were defined as grade ≥3 non-hematological toxicities, grade ≥3 immune-related adverse events, persistent grade ≥2 immune-related adverse events for more than 1 week despite optimal supportive care, or a radiotherapy delay greater than 1 week related to treatment toxicity. DLT were graded according to the Common Terminology Criteria for Adverse Events (CTCAE), version 4.03. Secondary endpoints included overall response rate (ORR), PFS, and treatment tolerance profile. The overall response rate was radiologically defined according to RECIST 1.1 criteria based on thoracic-abdominal-pelvic computed tomography, completed with pelvic MRI and 18F-FDG PET-CT evaluations. Exploratory analyses included immunological and molecular correlates of response to therapy.The study was based on a 3 + 3 design in order to confirm the safety of a flat dose of nivolumab at 240 mg q2wk; a maximum of one DLT for six patients was considered acceptable. A single reduced dose level (1-mg/kg) was planned. An expansion cohort of nine additional patients treated at the determined safe dose level was additionally planned. Consequently, the minimum sample size was 15 evaluable patients, and the maximum sample size was 21 evaluable patients. Patients who failed to complete the 11-week DLT evaluation period or who received less than 70% of the planned dose of nivolumab, of chemotherapy, or of radiotherapy for a reason other than DLT would be considered as not evaluable for the DLT assessment. A Data Safety Monitoring Board was consulted to review the safety profile of the treatment in the first six DLT evaluable patients and in order to proceed with the expansion cohort. The objective response rate (ORR) was defined as the proportion of all subjects whose best response was either a complete response (CR) or a partial response (PR), as assessed using RECIST. The PFS was defined as the duration from the start of the treatment to disease progression, date of last follow-up, or death, regardless of the cause of death. PFS was estimated by the Kaplan–Meier method. The survival analyses were performed using R v4.1.2 software.GraphPad Prism v9 software was used to perform the statistical analyses of the immunological correlates and the test used is indicated in the legend of each figure. Values were expressed as mean ± SEM or median of biological replicates, as specified. Without mention, differences are not statistically significant. Correlations were calculated using the nonparametric Spearman’s correlation test, two-tailed. The study protocol is available as Supplementary Note in the Supplementary Information File.