Conjunctival Melanoma in Aotearoa-New Zealand: A 21-Year Analysis of Incidence and Survival.

Abstract

Conjunctival melanoma (CM) is a rare and aggressive malignancy. Global studies demonstrate increased burden of disease in countries with high rates of cutaneous melanoma. There are currently no reports on CM incidence, trends, or survival within Aotearoa-New Zealand (NZ), a country with the highest global rates of cutaneous melanoma, which this study aims to address. This was a retrospective review using the national cancer registry. Data on histologically confirmed CM diagnosed between January 1, 2000, and December 31, 2020, were obtained from the NZ Cancer Registry. Cases were identified using the International Classification of Disease, 10th edition (ICD-10) codes. Primary outcome measures were age-standardized incidence, trends, and survival. A total of 68 CM cases were identified. There was a preponderance for females (n=40, 58.8%) and CM predominantly affected European patients (n=63, 92.6%). Median follow-up was 5.0 years [interquartile range (IQR)=2.4-9.9y] and the median age at diagnosis was 68.5 years (IQR=57.0-79.0y), with non-Europeans presenting at a significantly younger age [-17.3y (95% CI: -31.3 to -3.2), P =0.019] than Europeans. The annual age-adjusted incidence(±SD) was 0.6±0.2 cases per million population per year with a stable incidence trend over 21 years. All-cause mortality was found in 28 cases (41.2%) and the median time to death was 3.76 years (IQR=2.1-5.7y). Five-year all-cause survival and disease-specific survival was 69% and 90%, respectively. This is the first report on CM incidence, trends, and mortality in NZ. The CM burden is in line with European and North American data, despite NZ having the highest rate of cutaneous melanoma. The incidence remained stable over 2 decades.