Trends in the risks of melanoma as a second primary cancer among cancer patients in the Netherlands, 1989-2008

The aim of this study is to assess time trends of the risk of melanoma as a second primary cancer (MSPC) among cancer patients in the Netherlands during 1989-2008. Data from the population-based Netherlands Cancer Registry (NCR) were used for an analysis of time trends in the risk of MSPC in a fixed inception cohorts design (1989-1990, 1996-1997, and 2003), with similar lengths of follow-up. Standardized incidence ratios and absolute excess risks (AERs) were calculated to estimate the relative risks and excess absolute risks of MSPC. Differential time trends of risk in MSPC were observed, that is, decreasing for standardized incidence ratios and increasing for AERs in both sexes, but not reaching significance. Over time, AER changed from 24 to 72 per 10 000 person years (P for trend=0.01) in male patients with a previous melanoma during 2-5 years of follow-up, whereas among women with a first squamous cell carcinoma of skin, AER increased markedly (P for trend=0.3) over time during the first year of follow-up, coinciding with a decrease during the 2-5 years of the follow-up period (P for trend=0.1). MSPCs diagnosed later during follow-up were thicker than those diagnosed earlier, this difference being only statistically significant among male patients with a previous melanoma. The observed favorable risk trend among female patients coincided with thicker MSPCs than male patients. Differential risk trends were observed for MSPC among cancer patients during the past two decades in the Netherlands that did not seem to be affected by greater awareness of the disease. As the stage distribution of MSPCs worsened during follow-up, efforts should be made towards an earlier diagnosis of MSPC.