Melanoma epidemiology, prognosis and trends in Latvia.

Background Melanoma incidence and mortality rates are increasing worldwide within the white population. Clinical and histological factors have been usually used for the prognosis and assessment of the risk for melanoma. Objectives The aim of the study was to describe the clinical and histopathological features of the cutaneous melanoma (CM) in the Latvian population, to test the association between melanoma features and patient survival, and to assess the time trends for melanoma incidence. Methods We undertook a descriptive, retrospective analysis of archive data of 984 melanoma patients treated at the largest oncological hospital of Latvia, Riga East University Hospital Latvian Oncology Centre (LOC), between 1998 and 2008. Cox proportional hazards model was used to analyse patient survival and autoregressive models were applied to detect trends in melanoma incidence over time for various categories of melanoma. Results The study showed a significant ascending trend in melanoma incidence in Latvia during the time period from 1998 to 2008 (ss=1.83, 95% CI=1.15-2.91, P=0.011). Nodular melanoma was the most common tumour subtype with a frequency of 39.2%. Ulceration was present in 45.2% of melanomas. The mean Breslow thickness was 6.0 mm (6.8mm) and no significant decline in median Breslow thickness was observed during the study period (P=0.609). A better overall prognosis was detected for females in comparison with males (HR=1.49; 95% CI=1.22-1.81; P<0.001). Conclusions There is a steady increase in melanoma incidence in Latvia with the majority of melanomas diagnosed at late stages with poor prognosis for survival.