A population-based registry study on relative survival from melanoma in Germany stratified by tumor thickness for each histologic subtype

Background Differences in relative survival (RS) of melanoma between histologic subtypes were discussed to be mainly caused by tumor thickness. Objective To investigate RS of melanoma, stratified by tumor thickness for each histologic subtype, and identify survival trends. Methods With use of cancer registry data on melanoma cases ( International Classification of Diseases, 10th Revision , codes C43.0–C43.9) diagnosed in Germany in 1997–2013, 5- and 10-year age-standardized RS stratified by histologic subtype and stratified or standardized by T stage was estimated by standard and modeled period analyses. We restricted 10-year RS analyses to patients younger than 75 years. Results We analyzed 82,901 cases. Overall, the 5- and 10-year RS rates were 91.7% and 90.8%, respectively. Prognosis worsened with increasing T stage for all histologic subtypes, but T-stage distribution varied substantially. Survival differences by histologic subtype were strongly alleviated after adjustment for T stage but remained significant. Overall, 5-year RS increased significantly (by 3.8 percentage points) between the periods 2002–2005 and 2010–2013. This increase was no longer seen after adjustment for T stage. Limitations Exclusion of cases on account of missing information on T stages, changes in the definition of T stages, and lack of information on screening and treatment limit our analyses. Conclusion Differences in RS between histologic subtypes were strongly mediated by tumor thickness. Over time, RS of melanoma increased as a result of changes in T-stage distribution.