The researchers cautioned that there were some limitations to their findings - including that they didn’t have information on other possible risks for skin cancer, such as exposure to ultraviolet light, and not all Danish cancer cases were included in their registries.
One dermatologist not involved in the new study said to clarify the link between NSAIDs and skin cancer, a “gold standard” trial is needed - in which people are randomly assigned to take the drugs or not, then followed to see who develops cancer.
“More work needs to be done to examine this association,” said Dr. Maryam Asgari, a research scientist at Kaiser Permanente in Oakland.
“I don’t think I’d recommend to people, “Hey, take an aspirin a day to prevent skin cancer,” she told Reuters Health.
“I don’t think we have enough data to say that. I think we do have enough data to say, certain NSAIDs appear to be promising.”
After nine months of therapy, they found that the incidence of new actinic keratoses did not differ between the two groups. But after adjusting for a range of factors, including Fitzpatrick skin type and cancer history, there was a significant difference in the nonmelanoma cancers:
- On average there were 0.14 nonmelanoma skin cancers among the 122 celecoxib patients, compared to 0.35 among the 118 on placebo, yielding a relative risk of 0.41, which was significant at P=0.002.
- The mean number of basal cell carcinomas was 0.07 among the celecoxib patients and 0.16 among the placebo patients, leading to a relative risk of 0.40, which was significant at P=0.032.
- The average number of squamous cell carcinomas was 0.07 in the celecoxib group and 0.19 in the placebo group, giving a relative risk of 0.42, also significant at P=0.032.
- The researchers cautioned that all of the trial participants had extensive actinic damage and it’s not clear if celecoxib would have the same effect in other populations.
Adverse events - including cardiovascular events - were not significantly different between the study arms, they added.
The surprising fact that celecoxib reduced the number of nonmelanoma skin cancers but not the number of precancerous lesions hints that carcinogenesis may differ between early- and late-stage tumor development, according to Frank Meyskens Jr., MD, and Christine McLaren, MD, of the University of California Irvine.
Johannesdottir agreed that promoting painkiller use based on these findings isn’t warranted.
“Because there are also risks associated with the use of NSAIDs, we cannot give recommendations on NSAID use in general. It is up to the patient and his/her physicians to balance benefits and harms,” she said.
And, she added, “The most important prevention against skin cancer remains sun protection.”