Acral Lentiginous Melanoma: Incidence and Survival in the United States, 2006-2015, an Analysis of the SEER Registry.

BACKGROUND

Acral lentiginous melanoma (ALM) is one of the four major subtypes in cutaneous malignant melanoma (CMM). We aimed to study the incidence and survival of ALM in the United States in recent 10 y and compare the survival between ALM and nonacral CMM. In the meantime, racial disparity and prognostic factors associated with survival were investigated.

METHODS

All the cases of ALM registered in the Surveillance, Epidemiology, and End Results registry from 2006 to 2015 were retrieved, including non-Hispanic whites (NHW), black Americans (blacks), Asian/Pacific Islanders, and Hispanic whites. Age-adjusted incidence was calculated. Clinicopathologic data, including age, gender, race, geographic location, Breslow thickness, ulceration, pathologic staging, sentinel lymph node status, and surgical approach, were collected and analyzed. Melanoma-specific survival (MSS) was analyzed in patients with ALM and CMM. The Kaplan-Meier method was used to estimate the influence of clinicopathologic data on ALM MSS. Only cases with complete staging and active follow-up were included in prognostic factor analysis.

RESULTS

A total of 1724 ALM and 87,442 nonacral CMM patients were included in the study. For ALM patients, the age-adjusted incidence rate was 2.0 per million person-years. The proportion of ALM among all melanoma subtypes was greatest in blacks (32.6%). The 5-y MSS rates of ALM were lower than CMM overall (80.6% versus 93.0%, P < 0.001, respectively). When controlled by stage, the difference was significant in patients diagnosed at stages I and III. ALM 5-y MSS rates were highest (84.3%) in NHW, intermediate in Asian/Pacific Islanders (76.6%), Hispanic white (72.0%), and lowest in blacks (66.9%). Blacks were elderly, male predominant, located in East and Middle American, and had thicker, more ulcerated, advanced disease as compared with NHWs. When controlled by stage, survival difference was significant between NHWs and blacks in stage I (P = 0.004) and stage III (P = 0.005) patients. Gender, race, sentinel lymph node status, and pathologic stage were identified as independent risk factors in multivariate analysis.

CONCLUSIONS

The incidence of ALM has been steady in recent 10 y and more prevalent in aged people. ALM is associated with a worse prognosis than CMM. Black Americans have the worst prognosis, and survival difference is significant between NHW and blacks.