Published online May 15, 2022. doi: 10.4251/wjgo.v14.i5.1027
Peer-review started: December 10, 2021
First decision: January 12, 2022
Revised: January 24, 2022
Accepted: April 24, 2022
Article in press: April 24, 2022
Published online: May 15, 2022
Accurate target volume delineation is the premise for the implementation of precise radiotherapy. Inadequate target volume delineation may diminish tumor control or increase toxicity. Although several clinical target volume (CTV) delineation guidelines for rectal cancer have been published in recent years, significant interobserver variation (IOV) in CTV delineation still exists among radiation oncologists. However, proper education may serve as a bridge that connects complex guidelines with clinical practice.
To examine whether an education program could improve the accuracy and consistency of preoperative radiotherapy CTV delineation for rectal cancer.
The study consisted of a baseline target volume delineation, a 150-min education intervention, and a follow-up evaluation. A 42-year-old man diagnosed with stage IIIC (T3N2bM0) rectal adenocarcinoma was selected for target volume delineation. CTVs obtained before and after the program were compared. Dice similarity coefficient (DSC), inclusiveness index (IncI), conformal index (CI), and relative volume difference [ΔV (%)] were analyzed to quantitatively evaluate the disparities between the participants’ delineation and the standard CTV. Maximum volume ratio (MVR) and coefficient of variation (CV) were calculated to assess the IOV. Qualitative analysis included four common controversies in CTV delineation concerning the upper boundary of the target volume, external iliac area, groin area, and ischiorectal fossa.
Of the 18 radiation oncologists from 10 provinces in China, 13 completed two sets of CTVs. In quantitative analysis, the average CTV volume decreased from 809.82 cm3 to 705.21 cm3 (P = 0.001) after the education program. Regarding the indices for geometric comparison, the mean DSC, IncI, and CI increased significantly, while ΔV (%) decreased remarkably, indicating improved agreement between participants’ delineation and the standard CTV. Moreover, an 11.80% reduction in MVR and 18.19% reduction in CV were noted, demonstrating a smaller IOV in delineation after the education program. Regarding qualitative analysis, the greatest variations in baseline were observed at the external iliac area and ischiorectal fossa; 61.54% (8/13) and 53.85% (7/13) of the participants unnecessarily delineated the external iliac area and the ischiorectal fossa, respectively. However, the education program reduced these variations.
Wide variations in CTV delineation for rectal cancer are present among radiation oncologists in mainland China. A well-structured education program could improve delineation accuracy and reduce IOVs.
Core Tip: Accurate clinical target volume (CTV) delineation is essential to ensure appropriate tumor control while minimizing the exposure of surrounding normal tissues. However, a large degree of variation in CTV delineation for rectal cancer still exists, despite the availability of several CTV delineation guidelines. Our study aimed to evaluate the impact of an education program on CTV delineation for rectal cancer. The results first confirmed the wide variations in CTV delineation for rectal cancer among radiation oncologists from mainland China and proved that a well-structured education program could improve the accuracy and consistency of delineation.