Burden of malignancy after a primary skin cancer: recurrence, multiple skin cancers and second primary cancers.

The current paper summarizes relevant recent research on the high risk of recurrence, multiple skin cancers and second primary cancers in the growing number of people with a history of skin cancer; the ultimate purpose is to better assess the burden of malignancy following skin cancer. A number of challenges exist in identifying and tracking both melanoma and non-melanoma skin cancer (NMSC) cases. Most jurisdictions do not routinely track NMSC cases and, even if they do, it is customary to only include the first diagnosis. There are variable rules for counting multiple melanoma cancers, and recurrences are not considered for either major type of skin cancer. Applying insights from recent studies of this issue to Canadian cancer statistics would increase reported diagnoses of NMSC by about 26% and melanoma by 10% in this country. This approach to a fuller assessment of the burden of skin cancers has been called a "diagnosis-based incidence approach" as compared with a "patient-based incidence approach". A further issue that is not usually taken into account when assessing the burden of skin cancers is the 20% to 30% elevated risk of noncutaneous second primary cancers following a primary skin tumour. In summary, individuals with skin cancer are subject to a high risk of recurrence, multiple skin cancers and second primary cancers. This burden should be a special concern in the large and growing pool of individuals with a history of skin cancer, as well as among prevention planners.