OBJECTIVE: To evaluate the occurrence and causes of unplanned interruption of radiotherapy. MATERIALS AND METHODS: Retrospective study developed in the Division of Radiotherapy of Hospital Alemão Oswaldo Cruz in São Paulo, SP, Brazil, with data collected from 560 dossiers of patients submitted to radiotherapy in the period between January 1, 2005 and December 31, 2005. Chi-squared and Student t tests were utilized in the data analysis, and p < 0.05 was considered as statistically significant. RESULTS: Interruption of treatment was identified in 350 cases, corresponding to 62.5% of the patients. The reasons for treatment interruption were the following: preventive device maintenance (55%), patient's own private reasons (13%), adverse reactions to the treatment or to combined radiotherapy/chemotherapy (6%), clinical worsening (3%), two or more combined reasons (23%). The interruption time interval ranged between 1 and 24 days (mean 1.4 day). One-day interruption was mostly due to preventive device maintenance (84.4%); two-five-day interruption was due to combined reasons (48.28%). CONCLUSION: The most frequent cause of interruption was preventive device maintenance, with maximum two-day time interval.

Keywords: Radiotherapy, Cancer, Interruptions, Treatment