Tumour thickness of limited prognostic importance in acral melanoma

In acral melanoma (AM) patients with Breslow thickness >2 mm, tumour thickness does not appear to affect survival, a recent study has found.

The researchers conducted a multicentre retrospective analysis of 853 AM patients in whom the primary outcome of melanoma-specific survival (MSS) was assessed. Factors assessed included baseline sociodemographics, Breslow tumour thickness, primary tumour site, tumour ulceration, and stage at diagnosis.

Two patient populations were defined for analysis: clinical N0 (cN0) patients, including those with stage I/II AM, and pathological N0 (pN0) patients, including those with localized T1 melanoma or pathologically confirmed T2–T4 melanoma.

After a median follow-up of 60.1 months, the researchers recorded an overall median MSS of 109.0 months, with 5- and 10-year MSS rates of 66.8 percent and 45.9 percent, respectively.

Cox proportional hazards model showed that Breslow thickness, as a continuous variable, was significantly correlated with MSS in the pN0 (hazard ratio [HR], 1.10, 95 percent confidence interval [CI], 1.02–1.17; p=0.008) and cN0 (HR, 1.05, 95 percent CI, 1.02–1.08; p=0.005) subgroups.

Dividing patients into subgroups of Breslow thickness revealed that MSS was significantly better in those with ≤1-mm (HR, 0.28, 95 percent CI, 0.17–0.47) and >1–2-mm (HR, 0.58, 95 percent CI, 0.39–0.88), as opposed to tumours >6 mm.

Of note, MSS did not significantly differ in the following subgroups with tumour size >2 mm: >2–3, >3–4.3, >4.3–6, and >6 mm.

“The present study demonstrated that Breslow thickness has prognostic value in patients with localized AM. However, there was no association between tumour thickness and survival in patients with a Breslow thickness >2 mm,” the researchers said.

“These findings may help clinicians to stratify patients more accurately based on Breslow thickness and ulceration status, and thus to develop more precise treatment plans,” they added.