Fig. 1.

(a) Rectal DVH using four beam arrangements (median values plotted). ^∗Rectal V20% and V50% for one partial arc and two partial arcs significantly less than one full arc (p < 0.02). (b) DVH comparisons for 6 mm and 8 mm CTV to PTV margins (median values plotted). ^†PTV D95% significantly less using 8 mm margins compared to 6 mm margins (p < 0.005). ^∗Rectal/bladder V20%, V50%, V80% and V95% significantly less using 6 mm vs. 8 mm margins (p < 0.005). (c) DVH comparisons for CTV containing prostate alone and CTV containing prostate + proximal seminal vesicles (median values plotted), SV: seminal vesicles. ^†PTV D95% significantly less with prostate + proximal seminal vesicles in CTV compared to prostate alone (p < 0.005). ^∗Rectal/bladder V20%, V50%, and V80% significantly less with prostate alone in CTV compared to prostate plus proximal seminal vesicles (p ⩽ 0.005).