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Is the Pathologic Response of T3 Rectal Cancer to High-Dose-Rate Endorectal Brachytherapy Comparable to External Beam Radiotherapy?

Garfinkle, Richard, M.D.1; Lachance, Sebastian, M.D.1; Vuong, Te, M.D.2; Mikhail, Alexandre, M.D.1; Pelsser, Vincent, M.D.3; Gologan, Adrian, M.D.4; Morin, Nancy A., M.D.1; Vasilevsky, Carol-Ann, M.D.1; Boutros, Marylise, M.D.1

Diseases of the Colon & Rectum: March 2019 - Volume 62 - Issue 3 - p 294–301
doi: 10.1097/DCR.0000000000001220
Original Contributions: Colorectal Cancer
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BACKGROUND: Endorectal brachytherapy is an attractive option in the neoadjuvant setting for locally advanced rectal cancer, but it is not considered standard of care.

OBJECTIVE: This study aimed to compare pathologic outcomes of patients with clinical T3 rectal cancer who underwent high-dose-rate endorectal brachytherapy with those who underwent conventional external beam radiotherapy.

DESIGN: This study is a retrospective chart review.

SETTINGS: This study was conducted in a single large tertiary academic colorectal surgery practice in Canada.

PATIENTS: Adult patients with MRI-staged T3 rectal adenocarcinoma treated with neoadjuvant radiotherapy followed by total mesorectal excision from 2007 to 2016 were included.

INTERVENTIONS: Neoadjuvant radiotherapy was delivered by high-dose-rate endorectal brachytherapy or conventional external beam radiotherapy.

MAIN OUTCOME MEASURES: Primary outcome was pathologic complete response, defined as ypT0N0. Secondary outcomes included tumor (T stage) and lymph node (N stage) downstaging and tumor regression grade.

RESULTS: Ninety-nine patients were identified as having clinical T3 rectal cancer based on blinded pretreatment MRI review. Mean age was 66.2 years (± 6.2) and 59 patients (59.6%) were male. Thirty-three patients were clinically node negative (33.3%), 45 had c-N1 disease (45.5%), and 21 had c-N2 disease (21.2%). Sixty-four patients (64.6%) underwent high-dose-rate endorectal brachytherapy and 35 (35.4%) underwent external beam radiotherapy. The high-dose-rate endorectal brachytherapy group had a lower median mesorectal depth of invasion (4 mm vs 5 mm, p = 0.010); all other preoperative tumor characteristics were similar in both groups. Eighteen patients (18.2%) achieved pathologic complete response: 12 in the high-dose-rate endorectal brachytherapy group and 6 in the conventional external beam radiotherapy group (18.8% vs 17.1%, p = 0.84). High-dose-rate endorectal brachytherapy was superior to conventional radiotherapy for tumor (T stage) downstaging (59.4% vs 28.6%, p = 0.0030) but not for lymph node (N stage) downstaging (35.9% vs 51.4%, p = 0.14).

LIMITATIONS: This study was limited by its retrospective nature and modest sample size.

CONCLUSIONS: Neoadjuvant treatment of T3 rectal cancer with high-dose-rate endorectal brachytherapy appears to achieve equivalent rates of pathologic complete response and superior T-stage downstaging compared with conventional external beam radiotherapy. See Video Abstract at http://links.lww.com/DCR/A905.

1 Division of Colon and Rectal Surgery, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Canada

2 Division of Radiation Oncology, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Canada

3 Department of Radiology, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Canada

4 Department of Pathology, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Canada

Funding/Support: None reported.

Financial Disclosures: None reported.

E-poster presentation at the meeting of The American Society of Colon and Rectal Surgeons, Seattle, WA, June 10 to 14, 2017.

Correspondence: Marylise Boutros, M.D., McGill University, Jewish General Hospital, 3755 Cote Ste Catherine, G-317, Montreal, Quebec H3T 1E2, Canada. E-mail: mboutros@jgh.mcgill.ca

© 2019 The American Society of Colon and Rectal Surgeons