EP367 - Variation In Surveillance Following Non-Operative Management Of Rectal Cancer And Impact On Oncologic Outcomes: A Multicenter Cohort Study

ePoster Presenter(s)

• 

  Anthony Loria, MD

  Resident
  University of Rochester Medical Center
  University of Rochester Medical Center
  Rochester, NY, United States

  Disclosure information not submitted.

Author(s)

• FC

  Fernando AB Colugnati, n/a

  Associate Professor
  School of Medicine/ Universidade Federal de Juiz de Fora
  Juiz de Fora, Minas Gerais, Brazil

  Disclosure information not submitted.
• 

  Samuel H. Lai, MD

  Resident
  University of Colorado School of Medicine, Department of Surgery
  University of Colorado School of Medicine
  Aurora, CO, United States

  Disclosure information not submitted.
• MB

  Megan Boyer, MD (she/her/hers)

  General Surgery Resident
  University of Rochester
  University of Rochester
  Rochester, NY, United States

  Disclosure information not submitted.
• 

  Jon D. Vogel, MD

  Professor
  University of Colorado School of Medicine
  University of Colorado
  Aurora, Colorado, United States

  All of the relevant financial relationships listed below have been mitigated.
  This individual has no financial relationships with ineligible companies.
• 

  Wolfgang Gaertner, MD, MSc, MBA

  Professor and Chief, Colon & Rectal Surgery
  University of Minnesota
  University of Minnesota
  Minneapolis, MN, United States

  All of the relevant financial relationships listed below have been mitigated.
  This individual has no relevant relationships with ineligible companies.
• 

  John RT Monson, MD

  Attending
  Northwell
  Northwell Health
  New York, New York, United States

  Disclosure information not submitted.
• RC

  Robert Cleary

  Disclosure information not submitted.

Senior Author(s)

• FF

  Fergal Fleming, MD MPH FRCSI FACS

  Associate Professor of Surgery and Oncology
  University of Rochester Medical Center
  University of Rochester Medical Center
  Rochester, NY, United States

  All of the relevant financial relationships listed below have been mitigated.
  This individual has no relevant relationships with ineligible companies.

Purpose/Background: Non-operative management (NOM) following a clinical complete response (cCR) to neoadjuvant therapy allows patients with locally advanced rectal cancer to avoid proctectomy and preserve organ function. However, local regrowth occurs in up to one-third of patients and is associated with worse survival. Early detection through routine surveillance is critical to enabling salvage surgery. While expert guidelines recommend intensive MRI and endoscopic follow-up, real-world adherence in the U.S. is poorly characterized. Without national benchmarks or standardized protocols, it remains unclear how variation in surveillance affects oncologic outcomes. We hypothesized that most patients do not receive guideline-concordant surveillance and that inadequate surveillance is associated with delayed detection of local regrowth.

Methods/Interventions: We analyzed data from the Rectal Cancer Research Group, a national, multicenter registry of patients with stage II-III rectal adenocarcinoma who achieved cCR after neoadjuvant therapy and were managed non-operatively between 2015 and 2022. Locoregional surveillance with MRI and endoscopy was categorized as ideal, adequate, or inadequate per NCCN guidelines. Primary outcomes were local regrowth and distant metastasis. Multivariable Cox regression evaluated the association between surveillance intensity and oncologic outcomes. Predictors of adherence were assessed using a Bayesian multilevel model.

Results/Outcomes: Among 472 patients across 32 institutions, 55.3% received ideal surveillance; 21.2% had inadequate surveillance; and 9.3% of patients were lost to follow-up. Surveillance adherence varied widely by center, with ideal surveillance rates ranging from 20% to 77%. High-volume centers were more likely to deliver guideline-concordant care. Patients with inadequate surveillance experienced significantly delayed detection of local regrowth (median 19.4 vs. 9.1 months for ideal, p< 0.001). Risk of timely regrowth detection was over 5-fold higher with ideal surveillance (HR 5.2, p=0.007). No significant difference in distant metastasis was observed across surveillance levels.

Conclusion/Discussion: This study demonstrates substantial variability in surveillance practices for patients undergoing NOM for rectal cancer, with one in five patients receiving inadequate follow-up. Inadequate surveillance was associated with delayed regrowth detection, potentially compromising timely salvage. These findings underscore the urgent need for standardized surveillance protocols to ensure safe implementation of NOM. Institutional support and national benchmarks will be critical to improving adherence and optimizing outcomes as NOM becomes more widely adopted.

Figure 1: Probabilities of surveillance by institutional volume
Probability of ideal (A) and adequate (B) surveillance by institutional volume of patients with non-operative management
Figure 2: Time to outcome over the first three years of surveillance
Time to detection of local regrowth (A) and distant metastasis (B) by intensity of locoregional surveillance