Whole-mount pathologic analysis of rectal cancer following neoadjuvant therapy: implications of margin status on long-term oncologic outcome.

OBJECTIVE

Extent of distal resection margins in rectal cancer surgery remains controversial. We set out to determine the long-term oncologic impact of resection margins in patients with locally advanced rectal cancer using a comprehensive pathologic whole-mount section analysis.

BACKGROUND

It has been demonstrated that there is minimal disease beyond the gross tumor margin after neoadjuvant combined modality therapy (CMT) for rectal cancer. Although this suggests that close resection margins may be used for sphincter preservation, the long-term oncologic impact of this approach is unclear.

METHODS

We prospectively enrolled 103 patients with locally advanced rectal cancer after neoadjuvant CMT. Whole-mount pathologic analysis was performed, and clinicopathologic variables were correlated with disease-specific survival (DSS).

RESULT

: Sphincter preservation was achieved in 80% of patients, and the median distal margin was 2 cm (0.1 to 10 cm). There were 22 patients (21%) with distal margins 1 cm or less and no patient had a positive distal margin. Median radial margin was 1 cm and 4 patients (4%) had a margin of 1 mm or less. Viable distal intramural tumor spread was found in 3 patients (2.7%) and in all cases was limited to 1 cm or less from the gross tumor edge. At a median follow-up of 68 months, 5-year DSS was 86% and 1 patient experienced a local recurrence. Factors predictive of worse DSS included advanced tumor (T) and nodal (N) stage, tumor progression on neoadjuvant CMT, lack of a complete pathologic response, tumor location of 5 cm or less from the anal verge, and neurovascular invasion. The extent of the distal and radial margins of resection was not associated with DSS.

CONCLUSIONS

These results suggest that carefully selected patients with locally advanced rectal cancers who undergo neoadjuvant CMT can achieve excellent local control and DSS with a sphincter-sparing rectal resection and a margin distal clearance of 1 cm.