Dosimetric comparison of prostate radiotherapy between pelvic node-positive and node-negative patients

Background: The importance of dose in prostate radiotherapy is well known, and the dosimetric effects of radiotherapy in node-positive or node-negative patients with prostate cancer have become an important issue. Materials and Methods: Helical tomotherapy (TH) plans of 19 pelvic node-positive [THpn(+) plan] or node-negative [THpn(-) plan] patients with prostate cancer were retrospectively created in our clinic. In these plans, the beam angle was set to cover the planning target volume (PTV) of prostate cancer and minimize the dose to the organs at risk, including the bladder, rectum, femoral head, and bowel. Results: There were no differences in the conformity index, Dmax, Dmean, and homogeneity index of PTV between the THpn (+) and THpn (-) plans (p>0.05). However, V95 in the THpn (+) plan was lower than that in the THpn (-) plan (p=0.017). Moreover, Dmax, V75, V70, V65, V60, V50, V40, V30, and V20 for the rectum were not significantly different between the two plans (p>0.05), whereas Dmean was significantly different (p=0.025). Dmax, V70, V65, and V60 for the bladder were not significantly different between the two plans (p>0.05), whereas V55, V50, V40, and V30 were significantly different (p<0.05). Finally, Dmax and V50 for the femoral head and bowel were significantly different between the two plans (p<0.05). Conclusion: The THpn (+)] and [THpn(-) plans achieved acceptable target dose coverage in prostate radiotherapy.