Influence of cigarette smoking on the efficacy of radiation therapy in head and neck cancer

Abstract

Background: Smoking is a risk factor for several cancers and may also limit the efficacy of treatment. In this study, we evaluated the influence of cigarette smoking during radiation therapy on the efficacy of treatment in patients with head and neck cancer.

Methods: Using a questionnaire, we obtained information on smoking behavior at base line and weekly during therapy in 115 patients with head and neck cancer who were treated with radiation therapy with or without fluorouracil. The side effects of therapy were evaluated weekly, and response was assessed 13 weeks after treatment was completed. The main outcomes measured were treatment response and survival.

Results: The prognostic variables were similar among the patients who smoked and those who did not smoke during treatment. The 53 patients who continued to smoke during radiation therapy had a lower rate of complete response (45 percent vs. 74 percent, P = 0.008) and poorer two-year survival (39 percent vs. 66 percent, P = 0.005) than the 62 patients who did not smoke or who had quit before treatment. Among the nonsmoking patients, mortality was influenced by the length of time between quitting and treatment, with a risk reduction (relative to that for patients who continued to smoke) of 40 percent for patients who had quit less than 12 weeks before diagnosis and of 70 percent for patients who had quit more than 1 year before diagnosis. After adjustment for other variables with proportional-hazards regression analysis, smoking remained an independent prognostic factor (P = 0.002), with a relative risk of 2.5 (95 percent confidence interval, 1.4 to 4.4) favoring the patients who abstained from smoking. The results could not be explained by the type of chemotherapy received, the presence of coexisting morbid conditions, differences in the side effects of radiation, or the number of interruptions of treatment.

Conclusions: Patients with head and neck cancer who continue to smoke during radiation therapy have lower rates of response and survival than patients who do not smoke during radiation therapy.