Merkel Cell Carcinoma (MCC) is a rare skin cancer with a rising incidence worldwide. Anti-programmed death-1/ligand-1 (anti-PD-(L)1) therapies are effective for the treatment of advanced MCC. This study examines patterns of response / progression of advanced MCC to anti-PD-(L)1 therapies and describes subsequent management.
This is a multi-centre international retrospective cohort study with data collected up to May 2023 from 17 centres across 6 countries. Outcomes included objective response rate (ORR), duration of response (DOR), progression-free survival (PFS), and overall survival (OS) for anti-PD-(L)1 and subsequent therapy.
One-hundred and eighty-five advanced MCC patients received anti-PD-(L)1 therapy. At median follow-up of 28.7 months (95 % CI: 21.4-38.3), ORR was 57.3 %, median DOR was 42.8 months (95 % CI, 25.8 - not reached (NR)), median PFS was 14 months (95 % CI, 8.1- 19.8), and median OS was 42.8 months (95 % CI, 30.3 - NR). One-hundred and eight patients (59 %) experienced progressive disease; 50 % (n = 54/108) with primary resistance and 26 % (n = 28/108) with secondary resistance. Fifty patients (27 %; n = 50/185) received subsequent systemic therapies (+/- local therapy) with response data; 18 (36 %; n = 18/50) received doublet platinum chemotherapy (ORR 67 %, DOR 5.0 months [95 % CI; 3.7 - NR]) and 16 (32 %; n = 16/50) were rechallenged with anti-PD-(L)1 (ORR 56 %, DOR 20.2 months [95 % CI; 8.3 - NR]).
The most common subsequent treatment for patients with primary resistance was chemotherapy, while those with secondary resistance most frequently underwent further anti-PD-(L)1 therapy in combination with other therapies. Despite both therapies demonstrating promising ORR, doublet platinum chemotherapy had a poorer DOR compared to anti-PD-(L)1 rechallenge.