'Plan of the day' adaptive radiotherapy for bladder cancer using helical tomotherapy.

BACKGROUND AND PURPOSE

This study assessed the potential of tomotherapy based Image Guided Radiotherapy (IGRT) to increase the accuracy of bladder irradiation using a 'plan of the day' adaptive radiotherapy (ART) technique.

MATERIALS AND METHODS

Ten patients with muscle invasive bladder cancer underwent bladder preservation with trimodality therapy in an ongoing trial. All patients received 64 Gy/32# to the whole bladder and seven of them received a boost of 68 Gy/32# to the tumour bed. The ART technique entailed the generation of six IMRT plans for each patient, using six isotropic PTVs of 5-30 mm applied to the bladder volume (CTV) to generate the PTVs. Megavoltage CT (MVCT) imaging was done to correct positioning errors and choose the 'plan of the day'.

RESULTS

Post treatment MVCT scans (315 scans) were used to generate multiple anisotropic PTVs for three hypothetical scenarios. Overall, coverage of anterior and superior walls required larger margins than other walls. Maximum geographical miss, in spite of IGRT, was noted for the superior (13.8%) and anterior walls (10.3%).

CONCLUSIONS

Plan of the day ART is a feasible and promising technique for optimal treatment and dose escalation in bladder cancer.