[Sportschosun Reporter Jang Jong-ho] Radiation therapy is often administered after breast cancer surgery to eliminate any cancer cells that may remain. However, patients and their families have long worried that prolonged radiation exposure could damage skin cells and eventually lead to skin cancer. Previous studies conducted in the West reported that breast cancer patients who received radiation therapy had a 12% to 57% higher risk of skin cancer than those who did not. Most of those studies, however, focused on White patients, and large-scale studies involving Asians, including Koreans, have been limited.
A research team led by Professor Yoon Chang-ik of the Breast Cancer Center at the Cancer Hospital at The Catholic University of Korea, Seoul St. Mary’s Hospital, has reported that radiation therapy after breast cancer surgery does not increase the risk of developing skin cancer. The team included breast surgery professors Jin Je-hyun and Kim Du-re as co-first authors.
Using data from the Health Insurance Review & Assessment Service (HIRA), the researchers identified 83,437 patients aged 20 or older who were diagnosed with breast cancer—either invasive breast cancer or ductal carcinoma in situ—between 2009 and 2012. They then selected 52,510 patients who underwent surgery within one year of diagnosis. A total of 14,553 patients were excluded, including those diagnosed with another malignancy, including skin cancer, within two years before surgery or six months after surgery, and those who received chemotherapy, targeted therapy, or radiation therapy within one year before surgery. The final analysis included 37,957 patients. The researchers then used a statistical method to match the patients who received radiation therapy with those who did not as closely as possible in terms of age, sex, and history of other treatments. The two groups each included 9,928 patients, for a total of 19,856 patients.
The incidence of skin cancer was 0.97% among patients who received radiation therapy and 1.02% among those who did not, showing virtually no difference. Even when skin cancer was divided into melanoma, a malignant skin cancer arising from pigment-producing cells, and all other types of skin cancer, no difference in risk was found based on whether patients received radiation therapy. Both groups were followed for an average of approximately 11 and a half years, or 138 months.
Instead, the researchers identified factors that were actually associated with skin cancer. The risk was clearly higher among older patients, those with moles or precancerous skin lesions such as actinic keratosis and Bowen’s disease, and those with lymphedema in the limbs. Patients with moles had a 5.3-fold higher risk of skin cancer than those without moles, while those with skin lesions that could develop into cancer had a risk as much as 12.9 times higher. Patients with lymphedema also had approximately twice the risk of those without it.
The research team attributed the different findings from Western studies to racial differences and advances in treatment technology. White people are known to be more vulnerable to radiation damage than East Asians because they have less melanin pigment in their skin. In addition, many patients in earlier Western studies were treated when less precise two-dimensional radiation therapy planning was used. By contrast, the patients in this study were treated after three-dimensional conformal radiation therapy (3D-CRT) had become established, which may have reduced damage to normal skin.
The researchers cautioned that radiation-induced skin cancer can sometimes appear more than 20 years after exposure. Therefore, it is too early to draw definitive conclusions about long-term safety based solely on this study’s 11-year follow-up period, and further studies with longer observation periods are needed. They added, however, that because there were no significant differences between the radiation therapy and non-treatment groups in cumulative incidence curves or annual risk for overall skin cancer or its specific subtypes, no increase in skin cancer risk from radiation therapy was observed during the mid-term follow-up period of at least 10 years.
Professor Jin Je-hyun, the first author, said, "The side effects reported in the literature may differ somewhat from what is seen in actual clinical practice. This study is significant because it directly examined the outcomes of tens of thousands of patients who actually received treatment using health insurance claims data." He added, "I hope breast cancer patients can put aside their vague anxiety about developing skin cancer, focus on radiation therapy with peace of mind, and make a full recovery in good health."
Professor Yoon Chang-ik, who led the study, said, "Many patients and their families feel vague anxiety about skin cancer when preparing for radiation therapy after breast cancer surgery. This study provides evidence that currently used radiation therapy techniques do not particularly increase the risk of skin cancer." He added, "Because moles, precancerous skin lesions, and lymphedema emerged as the main risk factors, the findings suggest that systematically screening for and managing these high-risk skin conditions is more important in caring for breast cancer survivors than focusing on whether they received radiation therapy."
The study was published in the British Journal of Cancer.
Jang Jong-ho, Reporter bellho@sportschosun.com
This article has been translated by GripLabs Mingo AI.
