Risks of different skin tumour combinations after a first melanoma, squamous cell carcinoma and basal cell carcinoma in Dutch population‐based cohorts: 1989–2009

Background Skin cancer patients are primarily at increased risk of developing subsequent skin cancers of the same type. Shared risk factors might also increase the occurrence of a different type of subsequent skin cancer. Objective To investigate risks of different skin tumour combinations after a first melanoma, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). Methods All melanoma and SCC patients included in the national Netherlands Cancer Registry (NCR) and all BCC patients included in the regional Eindhoven Cancer Registry (ECR) between 1989 and 2009 were followed until diagnosis of a subsequent different skin cancer (melanoma, SCC or BCC), date of death or end of study. Cumulative risks, standardized incidence ratios (SIR) and absolute excess risks (AER) of subsequent skin cancers were calculated. Results A total of 50 510 melanoma patients and 64 054 patients with a SCC of the skin were included (national data NCR). The regional data of the ECR consisted of 5776 melanoma patients, 5749 SCC patients and 41 485 BCC patients. The 21‐year cumulative risk for a subsequent melanoma after a first SCC or BCC was respectively 1.7% and 1.3% for males and 1.3% and 1.2% for females; SCC after melanoma or BCC was 4.6% and 9.3% (males) and 2.6% and 4.1% (females); BCC after melanoma or SCC was respectively 13.2% and 27.8% (males) and 14.9% and 21.1% (females). SIRs and AERs remained elevated up to 21 years after the first melanoma, SCC or BCC. Conclusion This large population‐based study investigating risks of developing a different subsequent cutaneous malignancy showed high‐cumulative risks of mainly KC and markedly increased relative and absolute risks of all tumour combinations. These estimates confirm a common carcinogenesis and can serve as a base for follow‐up guidelines and patient education aiming for an early detection of the subsequent cancers.