Rates of anorectal melanoma rose substantially in the United States from 1992 to 2011, according to a study published in Dermatologic Surgery.
The increases affected men and women, said Dr. Adrienne Callahan of the department of dermatology, University Hospitals Case Medical Center, Cleveland, and her associates. Anorectal carcinoma was significantly more common among Hispanic whites than non-Hispanic whites (P = .02), “suggesting that this population may be targeted for screening interventions,” they added. (Dermatol Surg. 2016;42[1]:94-9). The highest rates were in Hispanic white elderly women.
Anorectal melanoma accounts for 1.3% of all melanomas and 16.5% of mucosal melanomas, and is most common among older women. The prognosis is often poor because the cancer tends to be asymptomatic until its late stages. To study the epidemiology of anorectal melanoma, the researchers analyzed data from the Surveillance, Epidemiology, and End Results 13 (SEER 13) Registries Database for 1992 through 2011.
The SEER database listed 260 cases for the study period. Most involved the rectum, 58% affected adults aged 65 years and older, and almost two-thirds occurred in women – a finding that dovetails with other studies, the researchers said. Notably, the estimated annual change in age-standardized incidence rates increased in both men (5.08%) and women (3.02%), which were statistically significant increases (P less than .05 for both trends).
Anorectal melanoma rates were significantly higher among Hispanic whites, compared with non-Hispanic whites. “Other studies have indicated that Hispanics are underscreened for skin cancer compared to other ethnic groups despite the increasing incidence of melanoma in this population,” said the researchers. “Although this may suggest a role for improved screening among those with Hispanic ethnicity, additional studies must be done to corroborate these results and further elucidate the association of Hispanic ethnicity with anorectal melanoma.”
As far as they know, this is the first study that has analyzed anorectal melanoma incidence in Hispanic whites and non-Hispanic whites, they added.
Ethnicity did not affect survival, which was generally poor. Anorectal melanoma is very rare, so the number of cases was relatively small and rates might have been unstable, the investigators noted. They added that it was not known whether the increases they found were related to improved detection.
The study was funded by the Char and Chuck Fowler Family Foundation, the Dermatology Foundation, and the National Cancer Institute. The researchers had no disclosures.