Rare vulvar malignancies; incidence, treatment and survival in the Netherlands

To describe trends in incidence, treatment and survival of patients with basal cell carcinomas and melanomas of the vulva. Also to compare survival of vulvar and cutaneous melanoma patients.

All women with a vulvar malignancy between 1989 and 2012 were selected from the Dutch Cancer Registry (n=6436). Standardized incidence rates, estimated annual percentage change (EAPC) and 5-year relative survival rates were calculated for basal cell carcinomas (BCCs) and melanomas. Patients with vulvar melanomas were matched to women with cutaneous melanomas on period of diagnosis, age, Breslow thickness, tumour ulceration, lymph node status and distant metastases. Differences in survival were evaluated using Kaplan-Meier curves and the log rank test.

489 women were diagnosed with a BCC and 350 with a melanoma of the vulva. The EAPC in incidence for melanomas was 0.2% and 1.1% for BCCs. Eighty-six percent of patients with BCC underwent surgical treatment in 1989-2006 and 95% in 2005-2012. Forty-five percent with BCC and 79% with melanoma were treated in a referral centre. Five-year relative survival for BCCs was 100% and for melanomas survival increased from 37% (95%CI 28-47%) in 1989-1999 to 45% (95%CI: 37-54%) in 2000-2012. Five years after diagnosis survival of women with vulvar melanoma was 15% lower compared to matched cutaneous melanoma patients (p=0.002).

No trends in age-adjusted incidence have been observed but more patients with BCC received surgical treatment over time. Having had vulvar BCC did not affect life expectancy. Well-known prognostic factors explained most of the differences in survival between cutaneous and vulvar melanoma patients, however a difference of 15% remained unexplained.