“Mandatory reporting of malignant diseases from independent sources to the CRN ensures virtual completeness and high-quality data, with 99.7% of the nonmelanoma skin cancers excluding basal cell carcinoma being morphologically verified.” says Mr Lergenmuller.
The study excluded women with very dark skin and who had prevalent melanoma or cSCC. Of the approximately 172,000 women enrolled in NOWAC, 159,419 women were included in the analysis, of which 95,552 (69.0%) reported ever use of indoor tanning. Among women with a history of indoor tanning, approximately 20% had a ≤10-year history of use, and approximately one- third started at age <30 years.
During a mean follow-up of 16.5 years, 597 women were diagnosed with cSCC. A potential dose-response relationship between indoor tanning use and development of cSCC was investigated by categorizing women into four groups by total number of lifetime sessions: 0 (never), 1-38 (lowest use), 39-240 (medium use), and >240 (highest use). The analysis found that compared with never users, the risk for cSCC development was significantly increased by 29% among lowest users, 60% among medium users, and 83% among women in the highest use group.
Compared with never users, women with a ≤10-year history of indoor tanning and those with a longer history of use had similar significantly increased risks of cSCC (41% and 43%, respectively). Women who started indoor tanning at age 30 or older had a 36% increased risk of cSCC relative to never users, and the risk for women who started indoor tanning at a younger age was increased significantly by 51%.
No association was found between age at initiation of indoor tanning and age at cSCC diagnosis. “We believe ours is the first study to investigate an association between age at initiation of indoor tanning and age at cSCC diagnosis,” Mr. Lergenmuller says.