Non-smokers fare better post-radiation

UC DAVIS (US) — Patients with head and neck cancer who have never smoked have much better survival rates after radiation therapy than patients with a history of smoking.

A first of its kind study finds patients with a history of smoking were more likely to die from their disease and more likely to experience a recurrence after radiation therapy than those without a smoking history.

Details are published in the American Journal of Clinical Oncology.

“There is something unique about the biology of head and neck cancers among non-smokers that makes them more amenable to cure by radiation therapy,” says Allen M. Chen, assistant professor of radiation oncology at the University of California, Davis.

“These tumors just melt after a few doses of radiation. If we could understand why, there would be important implications for new drugs and treatments.”

Chen suspects one possible explanation for the difference in response to radiation is human papillomavirus (HPV), a sexually transmitted disease that has been highly associated with head and neck cancer in people who have never smoked.

“The most common theory is that these tumors express a characteristic viral antigen on the cell surface that makes the immune system recognize the cancers more readily, which may enhance the effects of radiation,” he says.

“Another theory is that patients who have never smoked and who have HPV-related tumors have fewer mutations in key genes that are critical for radiation response.”

Chen compared 70 patients treated with newly diagnosed, non-metastatic squamous cell carcinoma of the mouth and throat who had a history of smoking with 70 patients with similar diagnoses who reported they had never smoked.

Patients who continued to smoke during treatment were not included in the study. Subjects were evenly matched based on age, gender, ethnicity, primary tumor site, disease stage and treatment history.

The analysis found that 14 of the 70 never-smokers experienced a recurrence of their disease compared to 26 patients who had a history of smoking.

In addition, 82 percent of never-smokers were disease-free after three years compared to 65 percent of patients who had smoked. Also, those who had never smoked had a lower incidence of complications related to treatment than those who had smoked.

The next step is to identify biological or genetic differences among smokers and never-smokers diagnosed with head and neck cancers and treated with radiation therapy that might account for the differences in prognosis, Chen says.

“We are in the process of conducting several laboratory experiments designed to better understand why cancers arising from never smokers are so exquisitely radiosensitive.”

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