The optimal surgical volume for anorectal melanoma: a retrospective analysis of the Russian Colorectal Cancer Society registry

Background. Anorectal melanoma is a rare malignancy without established standard treatment.
Aim. To analyse the Russian Colorectal Cancer Society melanoma registry and to assess optimal surgery with regard to the extent of the disease.
Materials and methods. A retrospective analysis of the Russian Colorectal Cancer Society registry was carried out during 2000–2020. Patients with cutaneous melanoma colonic metastases as well as patients with less than 6 months follow-up were excluded. Basic patient group characteristics, overall and disease-free survival (were analyzed depending on disease stage (by A. Stefanou) and surgery type.
Results. 16 patients had stage I–IIA, 24 – stage IIB, 29 patients – stage III and 24 patients – stage IV disease. Wide local excision was performed in 15 (93.8 %) patients with stage I–IIA, 15 (62.5 %) patients with stage IIB, 2 (6.9 %) patients with stage III, and 8 (33.3 %) patients with stage IV disease. Abdomino-perineal excision (APE) was performed in 0 patients with stage I–IIA, 7 (29.2 %) patients with stage IIB, 22 (75.9 %) patients with stage III, and 7 (29.2 %) patients with stage IV disease. 2-year overall survival was 74.5 % in stage I–IIA, 49.4 % in stage IIB, 64.3 % in stage III, and 10.4 % in stage IV disease; 2-year disease-free survival was 67 %, 23,4 %, 34,1 % in stage I–IIA, IIB, III disease accordingly. Median overall survival was 17.8 months, 38.3 months and 27.9 months for non-surgical treatment, wide local excision and APR in non-metastatic patients accordingly. Median disease-free survival was 6.0 months, 14.1 months and 12.0 months for non-surgical treatment, wide local excision and APR in non-metastatic patients accordingly.
Conclusions. APR should be considered in patients with stage IIB and stage III (by A. Stefanou) anorectal melanoma. Wide local excision is the preferred treatment in other patients.