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January 07, 2025
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Melanoma tumors thicker than 0.8 mm increase risk for death

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Key takeaways:

  • The crude incidence rate of melanoma-related death 20 years after diagnosis was 6% for those with tumors thinner than 0.8 mm.
  • The rate increased to 12% among those with tumors 0.8 mm to 1 mm in thickness.

The risk for melanoma-related death increased among patients with T1 melanoma tumors thicker than 0.8 mm, according to a study.

According to the American Joint Committee on Cancer (AJCC) 8th Edition Cancer Staging Manual, thin melanomas, characterized as less than 1 mm in Breslow thickness, are the largest group of all melanomas classified by tumor thickness as T1a or T1b.

DERM0125Lo_Graphic_01
Data derived from Lo SN, et al. JAMA Dermatol. 2024;doi:10.1001/jamadermatol.2024.4900.

“Reported 10-year and 20-year survival rates for patients diagnosed with thin melanomas are excellent,” Serigne N. Lo, PhD, associate professor at The University of Sydney and head of the research and biostatics group at the Melanoma Institute Australia, and colleagues wrote. “However, although the risk of death is low, around 25% of melanoma deaths worldwide are attributable to primary T1 melanomas.”

In light of this, the AJCC updated its staging guidelines in 2017, subcategorizing T1a and ulcerated T1b tumors with a 0.8 mm cutoff.

To determine if this change had any effect on the rates of melanoma-specific death, the authors examined the association between melanoma- and non-melanoma-related deaths for each 0.1 mm increase in Breslow thickness up to 1 mm.

The researchers accumulated data on 144,447 Australians diagnosed with thin, invasive primary melanomas between 1982 and 2014.

Results showed that the 0.8 mm cutoff makes an immense difference as the risk for melanoma-related death proved to increase significantly for patients with tumors of 0.8 mm to 1 mm Breslow thickness compared with those with thinner tumors.

The crude incidence rate of melanoma-related death 20 years after diagnosis was 6.3% (95% CI, 6.1%-6.5%) across the cohort and was even lower for those with tumors thinner than 0.8 mm (6%; 95% CI, 5.7%-6.2%). However, the melanoma-related death rate jumped to 12% (95% CI, 11.4%-12.6%) among those diagnosed with tumors 0.8 mm to 1 mm in thickness.

These rates corresponded with 20-year survival rates from diagnosis of 94.2% (95% CI, 94%-94.4%) for patients diagnosed with melanomas thinner than 0.8 mm and 87.8% (95% CI, 87.3%-88.3%) for those with tumors thicker than 0.8 mm. This rate was 91.9% (95% CI, 91.6%-92.1%) for the full cohort.

According to the authors’ multivariable analysis, patients with tumors of 0.8 mm to 1 mm thickness were significantly more likely to experience an absolute risk for melanoma-related death (subdistribution HR = 2.92; 95% CI, 2.74-3.12) and a greater rate of melanoma-related death (HR = 2.98; 95% CI, 2.79-3.18) compared with patients with thinner tumors.

The authors reported that these trends were not observed among patients with nonmelanoma skin cancer. They also concluded that staging for all T1 melanomas should consider these findings moving forward.

“These results suggest that a change of the T1 threshold from 1 mm to 0.8 mm should be considered when the AJCC staging system is next reviewed,” the authors wrote.