Analysis of acute toxicity with use of transabdominal ultrasonography for prostate positioning during intensity-modulated radiotherapy

Objectives. To analyze the effects of the B-mode ultrasound acquisition and targeting (BAT) system for positioning of patients with prostate cancer receiving intensity-modulated radiotherapy on acute gastrointestinal (GI) and genitourinary (GU) toxicity. Methods. The records of 50 consecutive patients treated using the BAT system were reviewed. Additionally, a comparison (no-BAT) group (ie, a group without a BAT study) treated in a similar manner was identified. The no-BAT group consisted of 49 patients treated immediately before the BAT group. For the two groups, the target definitions and dose prescriptions were identical, the treatment plan acceptance criteria were identical, and intensity-modulated radiotherapy was used for all patients. The daily BAT movements were charted in each of the three principal directions. Acute toxicity was scored for all patients according to the Radiation Therapy Oncology Group GI and GU acute toxicity scales. Results. The GU toxicity rates for the BAT versus no-BAT groups were grade 0 in 20% versus 14%; grade 1 in 38% versus 47%; grade 2 in 38% versus 39%; and grade 3 in 4% versus 0%, respectively (P = 0.284). The corresponding GI toxicity rates were grade 0 in 42% versus 27%; grade 1 in 28% versus 29%; and grade 2 in 30% versus 45% (P = 0.040). The incidence of GU and GI toxicity did not correlate with the directions or size of the BAT moves. Regression analysis revealed that for acute GI toxicity, the only variable reaching statistical significance was BAT use; no variable, including BAT use, reached statistical significance for acute GU toxicity. Conclusions. The use of the BAT system did not change the rate of acute GU toxicity but did reduce the rate of acute GI toxicity.