Treatment delays using an automated afterloading low-dose-rate brachytherapy system

Low-dose-rate (LDR) brachytherapy is an integral treatment modality in radiation oncology. Clinical efficacy is based on experience with manual source loading and continuous dose delivery. With remote afterloading technology, sources may be loaded and unloaded during the treatment course to prevent radiation exposure to nursing staff members and visitors. The aim of this study was to investigate treatment interruptions in terms of frequency and duration as well as extension of the overall treatment time period. The potential clinical impact of treatment interruptions was also considered.

The treatment records of 20 patients who underwent brachytherapy in the Indiana University Department of Radiation Oncology administered with a Selectron LDR remote afterloader were reviewed. Results were tabulated and analysis performed with respect to 1) the number of interruptions, 2) delay time, 3) delay time (T(d)) as a function of total implant time (T), 4) the time of day that each interruption occurred, and 5) the time in minutes of each individual interruption.

The mean number of interruptions was 44.9 per patient, (range, 24-76), with a mean prescription implantation duration of 45.7 hours and a mean actual treatment time of 51.2 hours resulting in a mean interruption time of 6.4 minutes per treatment hour. The number of interruptions was standardized and divided by the number of prescribed dose in grays, translating to 1.2 to 3.7 interruptions per gray delivered, with a mean of 1.6, resulting in an average T(d) of 11.21% (range, 7.35%-17.12%).

Significant interruptions are frequent using remote afterloading LDR techniques, reducing the effective dose rate. Careful monitoring of such interruptions is warranted.