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2019 GI Cancers Symposium: Rectal Cancer Treated With Total Neoadjuvant Therapy Plus Short-Course Radiation vs Concurrent Chemoradiation

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Key Points

  • Patients treated with short-course radiation/TNT achieved a numerically higher pCR rate compared to those treated with concurrent radiation.
  • Odds of achieving a low NAR Score were higher among the short course radiation/TNT cohort.
  • Recurrence rates were similar between the treatment groups over comparable follow-up.

The delivery of all radiotherapy and chemotherapy neoadjuvantly—also known as total neoadjuvant therapy—has improved complete response and downstaging rates compared to treatment after surgery in patients with rectal cancer. In a study presented by Chapman et al at the 2019 Gastrointestinal Cancers Symposium (Abstract 486), researchers looked at responses in patients treated with total neoadjuvant therapy and short-course radiation vs concurrent chemoradiation.

Study Background

The retrospective cohort study contained 388 eligible patients who had undergone neoadjuvant therapy followed by total mesorectal excision for stage II or III rectal cancer from 2009 to 2018. Concurrent radiation recipients (50–55 Gy in 25–28 fractions with concurrent fluorouracil [5-FU] or capecitabine) comprised one cohort; the other included short-course radiation/total neoadjuvant therapy recipients (25-35 Gy in 5 fractions followed by CAPOX [capecitabine, oxaliplatin] or FOLFOX [leucovorin, 5-FU, oxaliplatin] chemotherapy).

Researchers sought to compare the pathologic complete response rate, the Neoadjuvant Rectal (NAR) score—a validated predictor of outcome based on tumor downstaging—and recurrence rate between the two cohorts. The primary outcome of pathologic complete response rate was assessed in univariate analysis; the secondary outcome of NAR score was calculated and categorized as low (< 8), intermediate (8–16), or high (> 16). Recurrence rates were measured and classified as local, distant, or both.

Study Findings

A total of 236 patients (60.8%) were treated with concurrent radiation, and 152 were treated with short-course radiation/total neoadjuvant therapy.

On univariate analysis, the short-course radiation/total neoadjuvant therapy cohort had more advanced disease (77% stage III disease vs 67%, P = .04) and longer elapsed time between radiation completion and surgery (median = 131 vs 63 days; P < .01). Patients treated with short-course radiation/total neoadjuvant therapy achieved a numerically higher pathologic complete response rate compared to those treated with concurrent radiation (25.0% vs 19.1%, P = .16).

The odds of achieving a low NAR score were higher among the short-course radiation/total neoadjuvant therapy cohort, and recurrence rates were also similar (14.3% vs 14.9%, P = .87) over comparable follow-up.

The authors concluded, “Short-course radiation/[total neoadjuvant therapy] yielded a [pathologic complete response] rate of 25% and overall recurrence rate of 14.9% among patients with locally advanced rectal cancer. Short-course radiation with neoadjuvant multiagent chemotherapy is at least as effective as long-course concurrent radiation.”

Disclosure: The study authors' full disclosures can be found at coi.asco.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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