Non-melanoma skin-cancer, the most common type of cancer in the U.S., puts patients at an increased risk for potentially more serious cancers.

That’s why dermatologists and cancer groups are pushing patients who have a history of skin cancer to be more vigilant about regular checkups, the Wall Street Journal reports.

They are emphasizing the need for continued use of sunscreen, sun avoidance, and protective clothing, which can help prevent future malignancies even when sun damage has already been done.

After patients have had a basal cell carcinoma, the risk of another increases by 40 percent, according to the American Academy of Dermatology. Squamous cell cancers can also recur, often within two years.

Patients with both types of skin cancers are also are at increased risk for developing melanoma, the most deadly type. Recent studies have also found patients with non-melanoma skin cancers have an increased risk of a second primary cancer, including a breast and lung cancer in women and prostate cancer in men.

At highest risk are fair skinned, older people who have had a lifetime of sun exposure.

“No matter how much sun you’ve had, it always pays to correct your behavior,” says Darrell Rigel, M.D., a New York dermatologist. “If you fried in the sun all summer, you are most likely already in a high-risk category, so it isn’t a waste of time to be checked.”