Background: Patients with cutaneous melanoma (CM) on the trunk have a worse prognosis than those with extremity CM. One reason could be multiple or uncommon (outside axilla or groin) sentinel node locations (SNLs).
Methods: We identified 859 patients who underwent sentinel node biopsy for trunk (n = 465) or extremity (n = 394) CM in three Swedish healthcare regions from 2000 to 2008. We collected patient, tumor, and sentinel node characteristics through clinical registers and medical records. We investigated the distribution of SNLs in a logistic regression model, and risk of overall and melanoma-specific death through 2011 in a multivariable Cox regression model.
Results: Trunk CM was associated with multiple SNLs (31 vs. 7 %; odds ratio [OR] 7.1; 95 % confidence interval [CI] 4.6-11.5; p < 0.001) but not uncommon SNLs (8 vs. 7 %; OR 1.1; 95 % CI 0.6-1.9; p = 0.75) compared with extremity CM. The increased risk of melanoma-specific death was confirmed for trunk CM (hazard ratio [HR] 1.9; 95 % CI 1.3-2.9; p = 0.003), especially on the upper back (HR 2.3; 95 % CI 1.4-3.6; p < 0.001) compared with extremity CM. Uncommon SNLs (HR 0.5; 95 % CI 0.2-1.4; p = 0.21) or multiple SNLs (HR 1.1; 95 % CI 0.4-2.9; p = 0.81) were not associated with melanoma-specific death compared with those with common/single SNL.
Conclusions: Trunk melanomas were associated with multiple lymph drainage, but the worse prognosis of trunk melanomas could not be explained by the increased frequency of multiple or uncommon SNLs.