Side effects and quality of life after inadvertent radiation overdosage in brachytherapy of head-and-neck cancer

Purpose: By comparing our old (DP5, in use from 1978 to 1994) and new (Plato, Nucletron) dose planning system, we found that the old system underestimated doses by 20-25%. To study the possible consequences for the patients treated between 1978 and 1994, all who were still alive were invited to undergo an examination with respect to side effects and quality of life (QOL). Methods and Materials: The degree of overdosage was calculated by comparing the isodose distribution generated on the two dose planning systems. Eighty-four patients were then invited to undergo an examination with respect to side effects and QOL. The side effects were scored according to the LENT SOMA system and QOL according to European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Core 30 (QLQ-C30), and EORTC Quality of Life Questionnaire-Head and Neck 35 (QLQ-H and N35). Results: The mean overdosage of brachytherapy was 19.3%. No association was found between overdosage and side effects or QOL. For implants in the lateral border of the tongue, we found a statistically significant correlation between osteoradionecrosis and the following parameters: linear activity, total activity, dose rate, and extrapolated response dose. By multivariate analysis, only total implanted activity and the use of lead protection during brachytherapy were found to be of prognostic significance with respect to development of osteoradionecrosis. Conclusion: The incidence of side effects after brachytherapy at the Norwegian Radium Hospital seems to have been somewhat higher in the period under investigation than at other institutions. There may be several explanations, including the use of external beam radiotherapy before brachytherapy and departure from the Paris system among others. However, the side effects were not associated with the overdosage that was the basis for the study. As opposed to the general consensus of opinion, long-term QOL was found to be worse after brachytherapy than after external beam radiotherapy. This calls for increased awareness and a systematic prospective registration of the long-term side effects of brachytherapy