Influence of body habitus on dose parameters of nodal levels III to IV irradiation for breast cancer: comparison of 3 techniques.

This study aimed to investigate the effect of body habitus on supraclavicular (SC) dose-volume histogram (DVH) parameters among breast cancer patients according to 3 different techniques. Three SC irradiation plans were generated for 24 postoperative breast cancer patients: (1) direct antero-posterior field only (1fieldP), with dose prescribed to a 3-cm depth; (2) 3-cm depth plan (3cmP) using an antero-posterior field plus a posterior boost with the dose prescription defined to 3 cm; and (3) optimized plan (OptP) similar to 3cmP, with dose prescribed depending on the anatomy. The OptP plans had the least variation in DVH parameters with body habitus; 3cmP plans were the most varied. Conformity index among normal weight patients were 0.73, 0.78, and 0.87 (p = 0.02) and 0.61, 0.6, and 0.82 among overweight-obese patients for 1fieldP, 3cmP, and OptP, respectively (p < 0.001). V95% of the planning target volume among normal weight patients were 72.63%, 78.03%, and 87.18% for 1fieldP, 3cmP, and OptP, respectively (p = 0.02). The corresponding values among overweight-obese patients were 60.5%, 59.62%, and 81.62%, respectively (p = 0.001). Fixed depth dose prescriptions caused greater SC under dose than plans optimized according to patient's anatomy.