Adverse effect of treatment gaps in the outcome of radiotherapy for laryngeal cancer

Abstract

Background and purpose: A correlation has been demonstrated between unplanned prolongation of radiotherapy and increased local relapse. This review was performed to assess the importance of overall time on the outcome of curative radiotherapy of larynx cancer. Materials and methods: Retrospective analysis was performed of 383 patients with laryngeal cancer managed by elective radiotherapy between 1976–1988 in the Department of Clinical Oncology, University of Edinburgh, Western General Hospital, Edinburgh. All cancers were confirmed histologically to be squamous cell carcinomas. All subjects received radiotherapy in 20 daily fractions (except Saturdays and Sundays), employing individual beam direction techniques and computer dose distribution calculations. Main outcome measures were complete resolution of the cancer in the irradiated volume; local relapse; survival and cause-specific survival rates. Results: Radiotherapy was completed without any unplanned interruption (28 ± 2 days) in 230 383 (60%) of patients. A statistically significant two-fold increase in local relapse rates was observed when treatment was given in 31 days or more. There also was a statistically significant four-fold increase in laryngeal cancer deaths when the treatment time exceeded 30 days. Conculsions: In patients with laryngeal cancer, accelerated repopulation of cancer cells probably occurs after the start of radiotherapy. When the overall treatment time is 4 weeks or less, gaps at weekends are not detrimental. However, long holiday periods or gaps in treatment longer than 4 days increase the risk of laryngeal cancer relapse and cancer-related mortality. Significant gaps in treatment should be avoided. If treatment has to be prolonged, additional radiation dose should be prescribed to compensate for increased tumour cell proliferation.