Assessment of organ-at-risk sparing in esophageal cancer: a comparative dosimetric evaluation of hybrid, noncoplanar, and coplanar RapidArc plans

The purpose of this study is to improve the precision of radiation treatment and sparing of organ-at-risk (OAR) in patients with thoracic esophageal cancer (EC) affecting the heart, lung, and spinal cord. To improve and personalize cancer treatment plans, it assesses the dosimetric benefits of coplanar RapidArc (R_Ac), hybrid arc (RA_Hyb), and noncoplanar RapidArc (RA_nc). Fourteen patients with EC were chosen for our investigation from our hospital's database. RapidArc (RA) plan patients had already received treatment. Retrospectively, additional RAnc and RAHyb plans were made with a prescription dose of 50.4 Gy in 28 fractions for the planning target volume (PTV). A prescription dose of 95% of PTV was used, so that three different treatment planning procedures could be compared. The cumulative dose-volume histogram was used to analyze the plan quality indices homogeneity index (HI), conformity index (CI), conformation number (CN) as well as the OARs doses to the lung, heart, and spinal cord. In comparison to RAc and RAnc techniques, the study indicated that RAHyb plans significantly increased D95%, CI and HI, Dmax and CN did not differ substantially. In addition, compared to RAc (lung: 16.15 ± 0.03 Gy and heart: 23.91 ± 4.67 Gy) and RA_nc (lung: 15.24 ± 0.03 Gy and heart 23.82 ± 5.10 Gy) plans, RAHyb resulted in significantly lower mean lung doses (15.10 ± 0.03 Gy) and heart doses (21.33 ± 6.99 Gy). Moreover, the RAHyb strategy showed a statistically significant (P < 0.05) lower average MU (452.7) than both the RA_c (517.5) and RA_nc (566.2) plans. The D95%, conformity, and homogeneity indices were better for hybrid arc plans compared to RAc and RAnc plans. They also successfully managed to reduce the lung and heart doses as well as the mean MU per fraction. (author)