HIV, several diseases, and certain medicines used in treating organ transplants and other conditions all have something in common: they can weaken the immune system, leading to skin cancers.
The Trouble with Transplants
Organ transplant patients are particularly at risk. "Transplant patients have 64 times as many squamous cell carcinomas (SCCs, common skin cancers) as the general population. Heart transplant patients are at even greater risk," says Clark C. Otley, MD, Professor and Chair of Dermatologic Surgery, Mayo Clinic, College of Medicine, Rochester, MN.
To prevent organ rejection, transplant patients receive medications to suppress the immune system, the body's biological defense against infection, viruses, and disease. They are left even more vulnerable to skin cancer than patients who have HIV/AIDs or receive cancer chemotherapy.
While most skin cancers in the immunosuppressed are squamous cell carcinomas, basal cell carcinoma (BCC) presents a tenfold risk and melanoma a threefold risk, compared to the general population. Some rare skin cancers, such as Merkel cell carcinoma, also show up sometimes.
"I have patients who develop more than 100 squamous cell carcinomas in a year," states Dr. Otley. "Some have had 1,000 over a lifetime."
But without immunosuppressive drugs, there might not be a lifetime at all. Instead, more than 160,000 organ transplant recipients are alive in the U.S. alone.
HIV/AIDS Patients — At High But Not Highest Risk
While HIV/AIDS patients do not have as high a risk for skin cancer as transplant patients do, they are at seven times higher risk than the population at large. Once, many HIV patients suffered from the skin cancer Kaposi's sarcoma, but the numbers are way down; Dr. Otley attributes such improvement to Highly Active Antiretroviral Therapy (HAART), which reduces the amount of virus in the body. Many patients are now living with an immune system not far from normal. Still they have increased amounts of basal cell carcinomas on the torso as well as increased melanomas.
Leukemia and Other Cancers
Another disease that suppresses the immune system is chronic lymphocytic leukemia, a cancer of the lymph system said to have greater immune effects than other cancers. And several other types of cancer can put people at higher risk of developing skin cancer.
When the Immune System Weakens, Skin Cancers Can Skyrocket
Cancers present a double whammy, because in addition to cancer itself being immunosuppressive, so are the chemotherapies often used to treat them.
Arthritis, Lupus and Other Problems
Rheumatoid arthritis, lupus erythematosis and other autoimmune diseases (where the body attacks its own organs) also increase the risk of skin cancer. The drugs used to treat them are part of the problem. For example, prednisone, a steroid used to treat such conditions as arthritis and allergic reactions, can cause significant immunosuppression.
Last, but Not Least — The Sun
The sun's ultraviolet radiation not only can lead to sunburn, premature skin aging and skin cancer, but also can decrease immune system function. It can add to the immunosuppression stemming from organ transplantation, cancer, and other diseases.
"The last thing an immunocompromised person needs is sun exposure," warns Dr. Otley. Sunscreen appears to help. A study from Queensland, Australia, found that daily sunscreen use significantly reduces the number of squamous cell carcinomas that people develop over time.
"What I Tell My Patients"
Dr. Otley doesn't stop there. "I recommend a complete sun protection program, with sunscreen, clothes including a broadbrimmed hat and sunglasses, and shade or sun avoidance during peak hours," he says.
"If patients worry that reducing sun exposure will cause vitamin D depletion (the sun is a vitamin D source), I advise them to take supplements and maintain a vitamin D-rich diet, including such foods as salmon, egg yolks and fortified milk. Then I emphasize early detection, monthly skin self-examination, and a professional skin exam on the schedule the physician advises.
"Taking all these steps correlates with a lower incidence of skin cancer," he concludes. "This improvement holds true for even the most severely immunosuppressed."