Melanoma survival linked to tumor thickness

Researchers at The University of Sydney have identified a significant increase in melanoma-related death risk for patients with thin primary tumors measuring between 0.8 and 1.0 millimeters compared to those with thinner lesions.

Longstanding population-based data show thin cutaneous melanomas, usually defined as 1.0 millimeter or less, represent up to 72% of all melanomas by thickness. Australia, with the world’s highest incidence of melanoma, has maintained extensive cancer registries for decades, providing a unique context in which thin melanomas are widely recognized and routinely monitored.

Knowing how subtle increments in thickness correlate with survival outcomes could provide a clinical assessment rationale for long-term monitoring and management.

In the study, “Risk of Death Due to Melanoma and Other Causes in Patients With Thin Cutaneous Melanomas,” published in JAMA Dermatology, researchers conducted an analysis of Australian population-based registries from 1982 to 2014.

All patients were diagnosed with invasive melanomas measuring 1.0 millimeter or less in thickness. Data included age, sex, anatomical site, and detailed death records.

Investigators conducted both cause-specific and competing-risk analyses to ascertain long-term melanoma-related and nonmelanoma-related mortality. Breslow thickness measurements were considered by 0.1-millimeter increments to evaluate risk changes.

Of the 144,447 patients included, the overall melanoma-specific survival rate at 20 years was 91.9%, but survival rates diverged significantly between thickness groups. 94.2% of those with tumors under 0.8 mm survived, down to 87.8% for those measuring 0.8–1.0 mm.

Findings affirm the utility of the 0.8-mm Breslow thickness threshold in distinguishing high- and low-risk patients, supporting its continued inclusion in the American Joint Committee on Cancer staging criteria. The results also underscore the need for long-term follow-up in this patient population, as melanoma-related deaths continued to accumulate beyond 20 years.

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