NivoCUP: An open-label phase II study on the efficacy of nivolumab in cancer of unknown primary.
106 Background: CUP has a poor prognosis with a median survival of less than 12 months. Given the recent approval of immune checkpoint inhibitors in several cancer types, we performed a multicenter phase II study of nivolumab in CUP patients (pts). Methods: The main population of this study is CUP pts who were previously treated with more than one line of systemic chemotherapy. Previously untreated CUP pts were also enrolled for exploratory analysis. Pathological examination (including IHC), CT, FDG-PET, gastroscopy and colonoscopy and medical examination were mandatory for diagnosis of CUP before enrollment. CUP pts belonging to favorable prognosis groups were excluded from the trial. Nivolumab (240 mg/body) was delivered as an intravenous infusion every 2 weeks for up to 52 cycles until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) according to RECIST 1.1 by an Independent Endpoint Review Committee in previously treated pts. The secondary objectives include investigator-assessed ORR, progression-free survival (PFS), overall survival (OS), safety and the association between the efficacy of nivolumab and PD-L1 expression. Results: A total of 56 CUP pts, 45 previously treated and 11 previously untreated pts, were enrolled in this trial. The median age was 65.5 years, 22 pts were male. Median follow-up was 8.05 mo (range, 0.1 to 20.7 mo). Of 45 previously treated pts, 2 and 9 had an investigator-assessed complete response and partial response (ORR 24.4%, 95% CI: 12.9-39.5%), with a median PFS (mPFS) and OS (mOS) of 5.4 mo (95% CI: 2.6-6.9) and 15.1 mo (95% CI: 8.3-NR), respectively. Among 11 previously untreated pts, 1 pt had partial response (ORR 9.1%, 95% CI: 0.2-41.3%). The mPFS was 3.9 mo and the mOS was not reached in untreated pts (95% CI: 1.1-5.6, and 95% CI: 2.6-NR, respectively). Nivolumab demonstrated a mPFS of 5.1mo (95% CI: 2.7-5.6) and a mOS of 15.9 mo (95% CI: 8.4-NR) in an overall population. Immune-related adverse events occurred in 57% of overall pts with 5% of grade 3 or higher, and the most common were rash (27%), hypothyroidism (16%), and diarrhea/colitis (16%). No treatment related death was observed. Conclusions: In pts with previously treated and untreated CUP, nivolumab demonstrated durable antitumor activity with a manageable safety. Clinical trial information: UMIN000030649.