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Tumor Scatter After Neoadjuvant Therapy for Rectal Cancer: Are We Dealing with an Invisible Margin?

Hayden, Dana M. M.D.1; Jakate, Shriram M.D.2; Pinzon, Maria C. Mora M.D.1; Giusto, Deborah M.D.3; Francescatti, Amanda B. B.A.1; Brand, Marc I. M.D.1; Saclarides, Theodore J. M.D.4

doi: 10.1097/DCR.0b013e318269fdb3
Original Contribution: Colorectal/Anal Neoplasia

BACKGROUND: After the impressive response of rectal cancers to neoadjuvant therapy, it seems reasonable to ask: can we can excise the small ulcer locally or avoid a radical resection if there is no gross residual tumor? Does gross response reflect what happens to tumor cells microscopically after radiation?

OBJECTIVE: The aim of this study was to identify microscopic tumor cell response to radiation.

DESIGN: This study is a retrospective review of a prospectively collected database.

SETTING: This investigation was conducted at a single tertiary medical center.

PATIENTS: Patients were selected who had elective radical resection for rectal cancer after preoperative chemotherapy and radiation performed by 2 colorectal surgeons between 2006 and 2011.

MAIN OUTCOME MEASURES: The primary outcome measured was tumor presence after radiation therapy

RESULTS: Of the 75 patients, 20 patients were complete responders and 55 had residual cancer. Of these patients, 28 had no tumor cells seen outside the gross ulcer, and 27 (49.1%) had tumor outside the visible ulcer or microscopic tumor present with no overlying ulcer. Of these tumors, 81.5% were skewed away from the ulcer center. The mean distance of distal scatter was 1.0 cm from the visible ulcer edge to a maximum of 3 cm; 3 patients had tumor cells more than 2 cm distal to the visible ulcer edge. Tumor scatter outside the ulcer was not associated with poor prognostic factors, such as nodal and distant disease, perineural invasion, or mucin; however, it was associated with lymphovascular invasion (χ2 = 4.12, p = 0.038)

LIMITATIONS: There was limited access to clinical information gathered outside our institution.

CONCLUSIONS: Our study suggests that 1) after radiation, the gross ulcer cannot be used to determine the sole area of potential residual tumor, 2) cancer cells may be found up to 3 cm distally from the gross ulcer, so the traditional 2-cm margin may not be adequate, and 3) local excision of the ulcer or no excision after apparent complete response appears to be insufficient treatment for rectal cancer.

1 Department of General Surgery, Section of Colon and Rectal Surgery, Rush University Medical Center, Chicago, Illinois

2 Department of Pathology, Rush University Medical Center, Chicago, Illinois

3 Path Pathology Services, Justice, Illinois

4 Department of General Surgery, Division of Colon and Rectal Surgery, Loyola University Medical Center, Maywood, Illinois

Financial Disclosure: None reported.

Podium presentation at the meeting of The American Society of Colon and Rectal Surgeons, San Antonio, TX, June 2 to 6, 2012.

Correspondence: Dana M. Hayden, M.D., 2160 S. First Avenue, Maywood, IL 60153. E-mail: dhayden21@gmail.com

© The ASCRS 2012