Nivolumab for unresectable cutaneous epithelial malignancies: an open-label, single-arm, multi-centre, phase II trial (NMSC-PD1).

[BACKGROUND] Data in East Asian patients and in other epithelial skin cancers, including extramammary Paget's disease (EMPD) and adnexal carcinomas, are scarce. Therefore, we conducted a phase II trial of nivolumab in Japanese patients with advanced non-melanoma skin cancers (NMSCs).

[PATIENTS AND METHODS] This multicentre, open-label, single-arm phase II study enrolled adults (≥ 20 years) with histologically confirmed unresectable or recurrent epithelial cutaneous malignancies, Eastern Cooperative Oncology Group performance status 0-1, and at least one measurable lesion (RECIST v1.1). Nivolumab 480 mg was administered intravenously every 4 weeks for up to 26 cycles. The primary endpoint was overall response rate (ORR), assessed by blinded independent central review (BICR; RECIST v1.1). Secondary endpoints included progression-free survival, overall survival, and safety.

[RESULTS] Thirty-one patients were enrolled (20 cSCC, 4 EMPD, 2 BCC, 5 other NMSCs); median age was 73 years (range 58-86), and 71% were male. ORR by BICR was 22.6% (7/31), and the disease control rate was 54.8% (17/31). Responses were durable, with a median duration of 21.3 months. In the cSCC cohort, median tumour mutational burden (TMB) was 9.0 mut/Mb, lower than in Western series; among three patients with TMB ≥ 30 mut/Mb, two achieved objective responses. Common adverse events included pyrexia, hypothyroidism, adrenal insufficiency, and pruritus.

[CONCLUSIONS] Nivolumab showed durable antitumour activity with manageable toxicity in Japanese patients with advanced NMSCs, including rare non-cSCC. The lower ORR compared with Western trials may reflect intrinsic biological differences and support biomarker-driven, region-specific immunotherapy.

[CLINICAL TRIAL REGISTRATION] jRCT2031190048; registered 2 July 2019.