ADVERSE EFFECT OF TREATMENT GAPS IN THE OUTCOME OF RADIOTHERAPY FOR LARYNGEAL-CANCER

Background and purpose: A correlation has been demonstrated between un planned 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 metho ds: Retrospective analysis was performed of 383 patients with laryngea l cancer managed by elective radiotherapy between 1976-1988 in the Dep artment 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 dai ly fractions (except Saturdays and Sundays), employing individual beam direction techniques and computer dose distribution calculations. Mai n outcome measures were complete resolution of the cancer in the irrad iated volume; local relapse; survival and cause-specific survival rate s. Results: Radiotherapy was completed without any unplanned interrupt ion (28+/-2 days) in 230/383 (60%) of patients. A statistically signif icant two-fold increase in local relapse rates was observed when treat ment was given in 31 days or more. There also was a statistically sign ificant four-fold increase in laryngeal cancer deaths when the treatme nt time exceeded 30 days. Conclusions: In patients with laryngeal canc er, 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 peri ods or gaps in treatment longer than 4 days increase the risk of laryn geal cancer relapse and cancer-related mortality: Significant gaps in treatment should be avoided. If treatment has to be prolonged, additio nal radiation dose should be prescribed to compensate for increased tu mour cell proliferation.