Patterns of failure and implications for clinical target volume definition of locally advanced T4b rectal cancer identified with magnetic resonance imaging and treated using neoadjuvant chemoradiotherapy and surgery

• Published in: Radiotherapy and oncology Vol. 161; pp. 132 - 139
• Main Authors: Zhang, Yang-zi, Song, Maxiaowei, Geng, Jian-hao, Zhu, Xiang-gao, Li, Shuai, Li, Yong-heng, Cai, Yong, Wang, Wei-hu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2021
• Subjects: Clinical target volume; Neoadjuvant chemoradiotherapy; Patterns of failure; T4b rectal cancer; T4b rectal cancer; Clinical target volume; Neoadjuvant chemoradiotherapy; Patterns of failure
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2021.06.017

•Few studies have evaluated treatment failure patterns for pure T4b rectal cancer.•We evaluated the failure patterns after neoadjuvant chemoradiotherapy and surgery.•Locoregional recurrences were all below the S2-S3 junction.•Failure of external iliac node is scarce without prophylactic irradiation. Elective irradiation of the external iliac lymph nodes (EIN) has always been advocated for T4b rectal cancer with anterior organ invasion without convincing evidence. This study aimed to explore the patterns of treatment failure for locally advanced T4b rectal cancer treated using neoadjuvant chemoradiotherapy (NCRT) and surgery. This information may help to clarify whether the current definition of the clinical target volume (CTV) is still appropriate. We retrospectively analyzed data from 126 patients with locally advanced T4b rectal cancer who received NCRT, without elective EIN irradiation, followed by surgery between January 2010 and October 2018. Pretreatment magnetic resonance imaging was used to identify the T4b disease in all cases. The locoregional recurrence (LRR) rate and EIN failure rate were evaluated, and the LRR locations were identified using a three-dimensional model. After a median follow-up of 53.9 months, LRR occurred in 11.1% of patients (14/126). All LRRs were located in the previously irradiated fields and below the S2–S3 junction. The EIN failure rate was 0.8% (1/126) among all patients and 1.8% (1/56) in the group with anterior genitourinary organ invasion. The estimated 4-year distant relapse-free survival, disease-free survival and overall survival were 79.3%, 73.2% and 86.9%, respectively. It may be feasible to exclude the external iliac region from the CTV during NCRT for locally advanced T4b rectal cancer. However, further studies are needed to clarify whether the cranial border of the CTV can be lowered.