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Session: ePoster: Colon and Colorectal Cancer 7 (Sun350)

EP548 - Concordance Of Circulating Tumor DNA Trends With Pathology Results And Imaging Modalities In Rectal Cancer Patients Receiving Total Neoadjuvant Therapy

Sunday, May 11, 2025
4:06 PM – 4:11 PM PT
Location: Monitor 2, Sails Pavilion, Upper Level

    ePoster Presenter(s)

  • Lindsay Grasso, MD

    Resident Physician
    Bayhealth Medical Center
    Camden, DE, United States

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

    • Author(s)

  • AR

    Assar Rather, MD, FACS

    Colorectal Surgeon
    Bayhealth Medical Inc
    Dover, Delaware, United States

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

  • AF

    Adrianne Fisher, MSN, FNP-BC

    Nurse Practitioner
    Bayhealth Medical Center
    Dover, Delaware, United States

    Disclosure information not submitted.

All of the relevant financial relationships listed below have been mitigated.
Lindsay Grasso, MD: This individual has no financial relationships with ineligible companies.
Assar Rather, MD, FACS: This individual has no financial relationships with ineligible companies.
Image or Table (Do Not add text here):

Purpose/Background: We aim to compare circulating tumor DNA (ctDNA) trends with pathology and imaging results in patients receiving total neoadjuvant therapy (TNT) for rectal cancer.

Methods/Interventions: A retrospective chart review of a prospectively maintained database was performed to identify patients diagnosed with locally advanced rectal cancer treated with TNT and undergoing serial ctDNA testing. There were 14 patients included and a total of 84 blood draws.

Results/Outcomes: All 14 patients had a positive ctDNA prior to initiation of treatment. Eleven patients completed TNT. Of those, two patients had a complete clinical response with ctDNA clearance and are on a watch and wait protocol. Seven patients underwent definitive surgery and of those, five (71.4%) had negative ctDNA postoperatively. This was consistent with imaging and pathology results. Two patients had a positive ctDNA after surgery. One had a poor radiologic and partial pathologic response and was diagnosed with liver metastasis following surgery. The second patient with positive ctDNA had a good response on imaging and near complete pathologic response, but has remained persistently positive and is on close surveillance with no recurrence to date. There is one patient who had a partial clinical response and did not clear ctDNA after TNT who is awaiting definitive surgery. Another patient who initially cleared ctDNA after TNT is positive again which is consistent with persistent disease. However, due to a secondary primary malignancy, is not a candidate for definitive surgery.

The remaining three patients were planned to receive TNT. One of those patients had disease progression and continues to receive palliative chemotherapy and declined further ctDNA testing. The other two patients had rising ctDNA levels which corresponded with progression of their disease. One patient transitioned to hospice and the other patient was lost to follow-up after induction chemotherapy.

Conclusion/Discussion: Longitudinal monitoring of ctDNA may complement conventional tools to guide management and predict recurrence in patients with locally advanced rectal cancer.