Influence of dose-volume prescription in three-dimensional conformal radiotherapy for patients with stage III non-small-cell lung cancer

Dose-volume prescription (DVP) is usually used in intensity-modulated radiation therapy (IMRT) and point-dose prescription (PDP) is usually used in three-dimensional conformal radiotherapy (3DCRT) in Japan. This study aimed to retrospectively evaluate the impact of DVP instead of PDP on the doses and outcomes of 3DCRT for patients with lung cancer. Since 2011, the DVP has been used in place of the PDP in routine 3DCRT for patients with lung cancer in our institution. Twenty-one patients with stage III non-small-cell lung cancer who underwent definitive chemoradiotherapy using DVP were included this study. The patients received a prescribed dose of either 60 Gy or 66 Gy, both of which covered 95% of the planning target volume (PTV). The clinical target volume (CTV) was defined as the gross tumor volume plus a 5 mm or more margin, and the PTV was defined as the CTV plus a 5 mm or more margin. The median ratios of the dose in the DVP to that in the PDP were 1.059 and 1.077 in the actual treatment and in the planning study using unreduced PTVs, respectively. The median follow-up was 16.2 months. The overall 2-year Kaplan-Meier survival rate was 57%. The 2-year in-field control rates for the 66 Gy group and for the 60 Gy group were 100% and 0%, respectively. Although the PTVs were reduced, the DVP induced a 1.059-fold overdose. Meanwhile, treatment outcomes using the 66 Gy dose were satisfactory. (author)