Neoadjuvant chemoradiation and rectal cancer

Abstract

Neoadjuvant chemoradiation (NACR) is now standard of care in stage II and III rectal cancer. The advent of this modality of treatment has impacted on the way the pathological evaluation of resection specimens that have been subjected to preoperative chemoradiation is conducted. The gross description, sectioning and microscopic examination have had to be adapted to accommodate the changes induced by NACR. Attempts at introducing a uniform approach to the gross triaging and reporting of these specimens have been met with muted response. There still exists much variation in approach. The purpose of this overview is to highlight some of the newer developments and issues around NACR-treated rectal cancers from a pathological point of view. The NACR-treated resection specimens should be handled in a consistent manner, at least within individual institutions, if not universally. There should be generous sampling with multiple sections taken as tumour is often sequestered deep in the bowel wall. Microscopic examination should be extra vigilant as residual cancer can be present as single cells or small clusters, often deep in the muscularis propria or serosa. Acellular pools of mucin or non-viable tumour cells in mucin within the bowel wall or lymph nodes are not regarded as positive and do not upstage the tumour. The issue of grading of regression has been the subject of much debate, and several approaches have been published. It is recommended that a system that has clinical meaning and use to oncologists be used. Lymph node counts will be reduced after NACR, but reasonable attempts to accrue 12 nodes should be made.

Evaluating disparities in delivery of neoadjuvant guideline‐based chemoradiation for rectal cancer: A multicenter, propensity score‐weighted cohort study

“…These patients had lower odds of pathologic margin positivity and greater odds of inadequate nodal harvest associated with patients who received GBC. Chemoradiation has previously been shown to decrease the number of lymph nodes in an oncologic resection 24–27 . The decrease in lymph nodes has been previously explained by the effects of neoadjuvant chemoradiation in downstaging rectal cancer 15,23,28 .…”

MRI for nodal restaging after neoadjuvant therapy in rectal cancer with histopathologic comparison

“…Compared with HR-T2WI, this sequence offers advantages such as higher spatial resolution, improved signal-to-noise ratio, and multiplanar reconstruction, providing better-detailed of LNs. However, heterogenous enhancement could still be observed in benign LNs ≥ 5 mm, likely due to nodal fibrosis or the presence of acellular mucin lakes caused by neoadjuvant therapy [ 20 , 21 ]. Malignant LNs with smooth border, homogeneous signal intensity, and enhancement may contain micrometastases.…”

Comparison of oncologic outcome of abdominoperineal resection versus sphincter saving resection for low lying rectal cancer

“…Sphincter saving surgery (SSR) such as uLAR and ISR has recently increased with the better understanding of anal sphincter anatomy, enhanced surgical techniques, and neoadjuvant chemoradiation therapy (CRTx) [ 3 ]. Neoadjuvant CRTx contributes to enhancing the success rates of SSR (uLAR and ISR with CAA) by downstaging and downsizing the tumor [ 4 , 5 ]. Although SSR (uLAR and ISR with CAA) has recently been conducted more frequently, this surgery method can increase the potential recurrence risk.…”