Objective To compare the dosimetric characteristics of single-arc volumetric modulated arc therapy(VMAT) and 5-field dynamic intensity-modulated radiotherapy(dIMRT) for early-stage peripheral lung adenocarcinoma patients with spherical or spheroidal tumor lesions, and explore the appropriate curvature of single-arc VMAT.

Methods We collected 32 early-stage peripheral lung adenocarcinoma patients with spherical or spheroidal tumor lesions and designed three treatment plans for selected cases: single-arc 180° and single-arc 360° VMAT and 5-field dIMRT. The volume of each parameter was compared.

Results The three types of plans could meet all the dosimetric requirements of the clinical target area. There was no significant statistical difference in maximum dose(D_max), minimum dose(D_min), mean dose(D_mean), homogeneity index(HI) and conformity index(CI) of PTV among three groups (P > 0.05). The mean lung dose (MLD), V₅, V₁₀ and V₂₀ of the bilateral-lungs and affected-lung in the dIMRT plan group were lower than those of the other two single-arc VMAT plans, and those of single-arc 360° VMAT plan were slightly higher than those of the single-arc 180° VMAT plan (P < 0.05). D_mean of spinal cord was the lowest in dIMRT group and the highest in single-arc 360° VMAT group (P < 0.05). D_mean of esophagus in dIMRT group was less than those in the single-arc VMAT groups (P < 0.05). MUs was the lowest in dIMRT group and the highest in single-arc 360° VMAT group (P < 0.05).

Conclusion For early-stage peripheral lung adenocarcinoma patients with spherical or spheroidal tumor lesions, 5-field dIMRT is preferred; for single-arc VMAT, 180° single-arc is better.