There’s another reason for those at risk of skin cancer to stay vigilant about protecting their health.
Men and women with a history of non-melanoma skin cancer are at a higher risk of developing breast and lung cancers in addition to melanoma, compared to people without a skin cancer history.
Researchers from the Brigham and Women’s Hospital and Harvard Medical School discovered the connection after analyzing data from two large cohorts, the Health Professionals Follow-up Study and the Nurse’s Health Study, which included 153,612 participants. They found 36,102 cases of non-melanoma skin cancer, the most common type of skin cancer caused by overexposure to the sun’s ultraviolet rays, and 29,447 cases of other cancers such as prostate, melanoma, breast and lung cancer over a follow-up period of around 25 years.
Among those with a prior history of non-melanoma skin cancer, women had a 20% increased risk of developing another form of cancer other than melanoma, and men had a 11% higher risk. After the researchers accounted for other potential risk factors for developing tumors, they found that having non-melanoma skin cancer nearly doubled the risk of melanoma in men and increased risk of breast cancer by 20%, lung cancer by 32% and melanoma by more than two-fold among women.
Why non-melanoma skin cancers may contribute to other cancers isn’t entirely clear, but researchers have a few theories. The elevated risk of melanoma could be due to increased sun exposure; a recent study found that even skin cancer patients did not always take proper precautions in protecting themselves from tumor-triggering ultraviolet rays.
It’s also possible that non-melanoma skin cancer may share genetic or biological roots with other cancers; on overall weakness in cells’ ability to repair DNA damage caused by exposure to the sun, or other carcinogens, for example, may be driving higher risk different types of tumors. “It is biologically plausible that deficiencies of pathways responsible for protecting against cellular transformation in multiple tissues, such as DNA repair or immune responses, may act systemically and play a role in cutaneous and internal carcinogenesis,” the authors write in the study, which was published in the journal PLOS Medicine.
The body’s DNA repair system relies on a number of different pathways, however, and isolating which mechanisms might be responsible for a tendency toward abnormal cell growth could lead to better understanding of how the various cancers are connected. Previous studies have found, for instance, that the sex hormones estrogen and androgen are involved in regulating DNA repair in breast and prostate cancers; the latest results hint that they might also contribute to some types of skin cancers as well.
Because the study only found an association between non-melanoma skin cancers and other forms of cancer, the the researchers say they can’t recommend more rigorous screening of skin cancer patients — yet. But the connection strongly points to the need for more research to explore how a common mechanism may be driving several types of cancer. If that’s the case, then treatments targeting that pathway could yield more effective and broadly applicable treatments.