Prognosis for patients with thin cutaneous melanoma: long-term survival data from New South Wales Central Cancer Registry and the Sydney Melanoma Unit

Background: Estimates of long-term survival for patients with thin (< or = 1 mm) primary cutaneous melanomas vary widely. Two separate methods were used to study the survival of patients with melanoma from New South Wales (NSW), Australia, and from the Sydney Melanoma Unit (SMU).

Methods: The NSW Central Cancer Registry (NSWCCR) provided data on all patients who were diagnosed with cutaneous melanomas that measured < or = 1 mm thick between 1983 and 1998, inclusive. Patients with metastases at the time of diagnosis were not included, leaving 18,088 patients for analysis. The SMU data base was analyzed to extract data for all patients with thin melanomas who met the same criteria from 1979 to 1998, inclusive. All patients who had their primary tumors treated definitively elsewhere were excluded, leaving 2746 patients for analysis. Ten-year Kaplan-Meier survival rates were calculated, and significant differences were determined using log-rank analysis. Prognostic factors were evaluated with Cox proportional hazards analysis.

Results: The NSWCCR analysis revealed a 10-year survival rate of 96.4%. The 10-year survival rate for patients at SMU was 92.7%. Among the patients at SMU who died, the median time to recurrence was 49.8 months, and the median time to death was 65.9 months. The 10-year survival for patients at SMU who had lesions that measured < or = 0.75 mm was 96.9% compared with 84.3% for patients who had lesions that measured 0.76-1.0 mm. For patients who had ulcerated melanomas measuring < or = 1 mm thick, the 10-year survival rate was 83%, compared with 92.3% for patients who had nonulcerated melanomas.

Conclusions: The results of the current study confirmed the excellent survival rate for patients with thin melanomas. Higher-risk subsets of patients who may warrant consideration for aggressive investigation and treatment are identifiable.