[Daily online adaptive irradiation of bladder tumors with individualized safety margin creation].

AIM: Daily online adaptive radiation therapy (OART) allows the creation of individualized safety margins based on daily optimized treatment planning, taking into account daily anatomy variations. The goal of our work was to compare the protocols and safety margins of a non-adapted, image- guided radiation therapy (IGRT), a published Danish and the National Institute of Oncology of Hungary (NIO) protocol in the first eight bladder cancer patients treated with OART.

METHODS

Three cone beam CTs (CBCT) were taken during the first three fractions: after patient positioning, after adaptation, and at the end of treatment. Bladder contours, extensions and margins were established on all CT images (n=512). Intraadaptational, intrafractional and interfractional changes were examined.

RESULTS

Regarding PTV, a mean reduction of 12.2% could be achieved using the Danish, and 34.1% using the NIO protocol compared to IGRT. Healthy tissue irradiated by the prescribed dose could be reduced. The target volume miss is decreased as well.

CONCLUSIONS

PTV could be reduced and optimized, increasing healthy tissue protection using OART.