Physical and clinical implications of radiotherapy treatment of prostate cancer using a full bladder protocol

Purpose

To assess the dosimetric and clinical implication when applying the full bladder protocol for the treatment of the localized prostate cancer (PCA).

Patients and Methods

A total of 26 consecutive patients were selected for the present study. Patients underwent two series of CT scans: the day of the simulation and after 40 Gy. Each series consisted of two consecutive scans: (1) full bladder (FB) and (2) empty bladder (EB). The contouring of clinical target volumes (CTVs) and organs at risk (OAR) were compared to evaluate organ motion. Treatment plans were compared by dose distribution and dose?Cvolume histograms (DVH).

Results

CTV shifts were negligible in the laterolateral and superior?Cinferior directions (the maximum shift was 1.85 mm). Larger shifts were recorded in the anterior?Cposterior direction (95% CI, 0.83?C4.41 mm). From the dosimetric point of view, shifts are negligible: the minimum dose to the CTV was 98.5% (median; 95%CI, 95?C99%). The potential advantage for GU toxicity in applying the FB treatment protocol was measured: the ratio between full and empty bladder dose?Cvolume points (selected from our protocol) is below 0.61, excluding the higher dose region where DVHs converge.

Conclusion

Having a FB during radiotherapy does not affect treatment effectiveness, on the contrary it helps achieve a more favorable DVH and lower GU toxicities.