The influence of delineating criteria training on the delineation of tumor bed and whole breast target after breast-conserving surgery

Objective: To explore the influence of delineator and contouring criteria training on the delineation of the tumor bed and whole breast target after breast-conserving surgery. Methods: Twelve breast cancer patients after breast conserving surgery were selected. Tumor bed marked by clips was defined as gross target volume 1 (GTV₁), tumor bed formed by seroma was defined as GTV₂ and the whole breast was defined as clinical target volume (CTV). Five junior radiation oncologists first delineated GTV₁, GTV₂ and CTV for each patient following their own criteria. After contouring criteria training, they then delineated GTV₁, GTV₂ and CTV for the same group of patients again. The differences of the volumes of GTV₁, GTV₂ and CTV before and after training among different delineators were compared. One-way ANOVA or matching t-test was performed. Results: The inter-delineator variability on GTV₁, GTV₂ and CTV delineation before training was statistically significant (F = 11.16, 7.54 and 3.78, F = 0.000, 0.000 and 0.009). After training, the inter-delineator variability on GTV₁ and GTV₂ delineation had statistical significance (t = 4.78 and 4.24, P = 0.002 and 0.005), but the inter-delineator variability on CTV delineation had no statistical significance (t = 1.52, P = 0.209). The coefficient of variance of the GTV₁, GTV₂ and CTV before and after training was significantly different (t = 3.14, 2.81, 2.70, P = 0.009, 0.017 and 0.021). The matching index of GTV₁, GTV₂ and CTV before and after training was significantly different (F = 16.08, 8.61, 8.48, P = 0.000, 0.000 and 0.000). Conclusions: In delineating the target of breast cancer, application of the criteria of target delineation can reduce the difference among the delineators, especially for CTV. (authors)