Findings from a case-control study show that a history of indoor tanning is the strongest risk factor for the development of multiple primary melanomas (MPMs).
This research was published in the Journal of the American Academy of Dermatology.
The paper’s authors write that the literature shows that a history of more than 10 indoor tanning exposures is associated with an increased risk for melanoma. As well, the clinical experience of the authors is that indoor tanning is the most frequent cause of MPMs.
To investigate the relationship between indoor tanning and MPMs, the researchers conducted a case-control study involving 453 patients—335 with a single primary melanoma (SPM) and 118 with MPMs. Patients with SPM were the controls in the study. All the patients were aged between 20 and 70 years at the time of data extraction and had a diagnosis of at least one primary melanoma at the Northwestern Memorial Hospital between Jan. 1, 2015, and Dec. 31, 2018.
The patients were then stratified by a history of more than 10 lifetime indoor tanning exposures versus zero exposures.
Researchers found that 19% of patients with SPM had more than 10 exposures, compared to 53% of those with four or more MPMs. Both univariate and multivariable analyses showed that the associated risk for MPMs was significant for 2+, 3+ and 4+ melanomas (p<0.05).
Investigators also performed a systematic review of the literature and meta-analysis to compare the risk for MPMs associated with the most common germline mutations associated with familial melanomas.
Comparing risk associated with indoor tanning compared to other risk factors, the researchers found that at 2+ melanomas, the risk associated with indoor tanning surpassed that of family history and resembled the risk associated with germline mutations in MITF and MC1R. At these lower numbers of MPMs, a germline mutation in CDKN2A carried a greater risk compared to indoor tanning.
The data were limited for higher numbers of MPMs “but suggested that the risk related to indoor tanning may surpass that of low-/intermediate-penetrance germline mutations,” the authors write.
Because the prevalence of indoor tanning is higher than that of germline mutations in CDKN2A, clinicians are more likely to encounter patients with a history of indoor tanning compared to those with such mutations, the authors write. Therefore, this study’s findings emphasize the importance of educating the public about the risks of indoor tanning, and patients who use these devices might benefit from closer follow-ups from dermatologists.