Abstract 809P
Background
Acral (AM) and mucosal melanomas (MM) are rare subtypes with a poor prognosis. In those with advanced disease anti-PD-1 (PD1) therapy has reduced activity compared to that seen in non-acral cutaneous melanoma. While adjuvant (adj) PD1 is used for resected stage III/IV AM and MM, there are no data regarding efficacy in these subgroups.
Methods
Patients with resected stage III or IV AM or MM from 19 centres were included. Baseline disease characteristics, disease recurrence characteristics and treatment outcomes-recurrence free survival (RFS) and distant metastasis free survival (DMFS) were examined. Comparison has been made to matched historical data of patients who did not receive adjuvant therapy from the Melanoma Institute Australia (MIA) database.
Results
157 patients were identified, 100 (64%) Caucasian, 116 (74%) AM and 41 (26%) MM with a median age 65.5 (20-82) for AM and 59 (29-82)for MM. Of these patients 5 (5%) AM and 3 (7%) MM had resected stage IV disease. At a median follow up of 18 months, 65 (56%) AM and 29 (71%) MM had recurred. 34 (29%) of AM and 9 (22%) MM patients completed adjuvant PD1 therapy with 47 (41%) of AM and 19 (46%) of MM patients stopping adjuvant treatment due to recurrence. Median time to recurrence was 17.7 months for AM and 12.9 months for MM patients. First recurrence was locoregional alone in 33 (51%) of AM and 16 (55%) of MM patients . In those with resected stage III disease both median and landmark RFS and DMFS were not significantly different to that seen in the matched historical cohort (Table). Table: 809P
| Acral | Mucosal | |||
| Adj PD1 | Database matched | Adj PD1 | Database matched | |
| N | 111 | 90 | 38 | 12 |
| BRAF mutant % | 18 | - | 7 | - |
| Stage IIIC/D* % | 65 | - | 75 | - |
| Median RFS (months) | 17.35 | 17.4 | 18.8 | 11.65 |
| 1yr landmark RFS %, (95% CI) | 79 (70-88) | 71 (62-82) | 66 (43-99) | 80 (60-100) |
| 3yr landmark RFS % (95% CI) | 48 (38-62) | 47 (37-60) | - | - |
| Median DMFS (months) | 31.95 | 25.9 | 23.65 | 14.5 |
| 3yr landmark DMFS % (95% CI) | 78 (69-88) | 80 (71-91) | 53 (27-100) | 70 (46-100) |
*AJCCv8 cutaneous staging applied to AM/MM.
Conclusions
Resected AM and MM carries a poor prognosis irrespective of the use of adjuvant PD1. We did not observe an obvious benefit of adjuvant PD1 in RFS and DMFS compared to historical controls. Prospective studies in these subgroups are required to determine the utility of adjuvant PD1 therapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
J.K. Schwarze: Non-Financial Interests, Personal and Institutional, Invited Speaker: MSD, Amgen; Financial Interests, Personal and Institutional, Funding: Novartis. A.M. Menzies: Financial Interests, Personal, Advisory Board, advisory board: BMS, MSD, Novartis, Roche, Pierre-Fabre, QBiotics. M.S. Carlino: Financial Interests, Personal and Institutional, Advisory Role: Amgen, Eisai, Ideaya, Nektar, Oncosec, Pierre-Fabre, Qbiotics, Regeneron, Roche; Financial Interests, Personal and Institutional, Advisory Role, and honoraria: Bristol Myers Squibb, Merck Sharp and Dohme, Novartis. All other authors have declared no conflicts of interest.