Poor response at restaging MRI and high incomplete resection rates of locally advanced mucinous rectal cancer after chemoradiation therapy

Tijmen Koëter; Rutger C H Stijns; Sebastiaan van Koeverden; Niek Hugen; Joost Albertus Gerardus van der Heijden; Joost Nederend; Peter H van Zwam; Iris D Nagtegaal; Marcel Verheij; Harm J T Rutten; Johannes H W de Wilt

doi:10.1111/codi.15760

Poor response at restaging MRI and high incomplete resection rates of locally advanced mucinous rectal cancer after chemoradiation therapy

Colorectal Dis. 2021 Sep;23(9):2341-2347. doi: 10.1111/codi.15760. Epub 2021 Jun 22.

Affiliations

¹ Department of Surgery, Radboud University Medical Centre, Nijmegen, The Netherlands.
² Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
³ Department of Radiology, Catharina Hospital, Eindhoven, The Netherlands.
⁴ Department of Pathology, PAMM Laboratory for Pathology and Medical Microbiology, Eindhoven, The Netherlands.
⁵ Department of Pathology, Radboud University Medical Centre, Nijmegen, The Netherlands.
⁶ Department of Radiation Oncology, Radboud University Medical Centre, Nijmegen, The Netherlands.
⁷ Department of Surgery, Catharina Hospital, Eindhoven, The Netherlands.

Abstract

Aim: Mucinous carcinoma is a histological subtype of rectal cancer and has been associated with a poor response to neoadjuvant chemoradiotherapy (CRT). The primary aim of this study was to analyse the response on MRI of mucinous locally advanced rectal cancer (LARC) after CRT compared to regular adenocarcinoma.

Method: Patients with LARC (defined as cT4 and/or cN2), who underwent CRT followed by restaging MRI and surgery in two tertiary referral hospitals were retrospectively included in the study. Pre- and post-treatment MRI was reviewed by an experienced abdominal radiologist.

Results: A total of 102 patients, of whom 29 were diagnosed with mucinous carcinoma, were included for analysis. At restaging MRI, adenocarcinoma patients demonstrated significantly less clinical involvement of the mesorectal fascia (37% vs. 62%, P = 0.003) while this was not demonstrated in mucinous carcinoma patients (86% vs. 97%, P = 0.16). Significant downstaging after CRT in adenocarcinoma patients (P = 0.01) was seen while, in mucinous carcinoma patients, no downstaging after CRT (P = 0.89) was seen. Pathology revealed significantly higher rates of an involved circumferential resection margin in mucinous carcinoma versus adenocarcinoma patients (27.6% vs. 1.4%; P < 0.001). After multivariate regression analysis, mucinous carcinoma remained an independent prognostic factor for local recurrence (hazard ratio 3.6; 95% CI 1.1-12.4), although no differences in overall or disease-free survival were observed.

Conclusion: Mucinous rectal carcinoma is associated with a poor clinical response at restaging MRI after CRT, leading to relatively higher rates of involved circumferential resection margins at pathology. In this cohort, mucinous carcinoma seems to be a prognostic factor for increased risk of local recurrence, without an effect on overall survival.

Keywords: MRI; chemoradiotherapy; locally advanced; mucinous rectal cancer; neoadjuvant treatment; rectal cancer; response evaluation.

MeSH terms

Chemoradiotherapy
Humans
Magnetic Resonance Imaging
Neoadjuvant Therapy
Neoplasm Recurrence, Local* / diagnostic imaging
Neoplasm Recurrence, Local* / therapy
Neoplasm Staging
Rectal Neoplasms* / diagnostic imaging
Rectal Neoplasms* / pathology
Rectal Neoplasms* / therapy
Retrospective Studies
Treatment Outcome