Evaluation of variability in seroma delineation between clinical specialist radiation therapist and radiation oncologist for adjuvant breast irradiation

Abstract

Breast cancer is managed by a multidisciplinary team with a goal for the timely provision of high quality care. Given radiation oncologist (RO) time constraints, an opportunity arises for task delegation of breast seroma target delineation to an advanced practice clinical specialist radiation therapist (CSRT) with clinical and technical expertise to facilitate treatment planning. To explore this further, we quantitatively evaluated the variability in post-surgical seroma delineation between the CSRT and ROs. Specialized site specific training was provided to the CSRT, who, with 7 ROs, independently contoured the seroma and graded its clarity, using the cavity visualization score (CVS), for 20 patients with clinical stage Tis-2N0 breast tumors. The conformity indices were analyzed for all possible pairs of delineations. The estimated "true" seroma contour was derived from the RO contours using the simultaneous truth and performance level estimation algorithm. Generalized kappa coefficient and center of mass metrics were used to examine the performance level of the CSRT in seroma delineations. The CVS of the CSRT correlated well with the mean RO-group CVS, (Spearman ρ = 0.87, P < .05). The mean seroma conformity index for the RO group was 0.61 and 0.65 for the CSRT; a strong correlation was observed between the RO and CSRT conformity indices (Spearman ρ = 0.95, P < .05). Almost perfect agreement levels were observed between the CSRT contours and the STAPLE RO consensus contours, with an overall kappa statistic of 0.81 (P < .0001). The average center of mass shift between the CSRT and RO consensus contour was 1.69 ± 1.13 mm. Following specialized education and training, the CSRT delineated seroma targets clinically comparable with those of the radiation oncologists in women with early breast tumors suitable for accelerated partial breast or whole breast radiotherapy following lumpectomy. This study provides support for potential task delegation of breast seroma delineation to the CSRT in our current multidisciplinary environment. Further study is needed to assess the impact of this role expansion on radiotherapy system efficiency.