Beam's eye view based prostate treatment planning: is it useful?

Prostate cancer is a common malignancy often treated with radiation therapy. Treatment optimization may improve local control while reducing acute and long-term complications. We routinely obtained CT scans on prostate cancer patients in treatment position after simulation. We analyzed the impact and implications of using our 3-D Beam's Eye View (BEV) capability on field definition and blocking for 12 consecutive patients. Conclusions include: (a) it is necessary to use multiple bony landmarks to align BEV images with simulator films; (b) it is difficult to enter volumes precisely, that is, the exact inferior extent of prostate; (c) Beam's Eye View-based plans show more individual variability in field size and position than are allowed for by recommendations in the literature; and (d) in this small series we found no significant correlation between prostate volume and clinical staging. In addition, computerized Beam's Eye View capability enables us to do normal tissue dosimetry. We have used Dose Volume Histograms (DVH) to study the impact of Beam's Eye View on optimization of dose to the bladder and rectum while adequately treating the prostate, with or without the seminal vesicles. Dose Volume Histograms using Beam's Eye View are compared with Dose Volume Histograms using target volumes from the literature. The results will be discussed, as well as the relative advantages of using Beam's Eye View for prostate cancer on a routine basis.