Role of intraoperative frozen section for assessing distal resection margin after anterior resection

The use of neoadjuvant long-course chemoradiotherapy (LCRT), shorter distal safety margins (DSMs) and stapled or intersphincteric resections has increased sphincter preservation rates. While intraoperative frozen section (IOFS) is not mandatory, it helps achieve negative distal resection margins (DRMs). Our aim was to audit the role of IOFS for DRM assessment while performing sphincter-saving rectal surgery and to identify those subgroups that would benefit the most from IOFS analysis.

Patients who underwent rectal cancer surgery between 2009 and 2013 were identified from a prospectively maintained database. Patients who intraoperatively underwent an IOFS for DRM assessment were included in the study. Factors associated with a positive margin on IOFS were analysed. The sensitivity and specificity of IOFS were also assessed.

Of 250 patients, who had an anterior resection with an IOFS, 12 had an involved DRM. Of these patients, eight were involved by adenocarcinoma, two by acellular mucin, one by moderate dysplasia and one by adenoma confirmed on paraffin section. Positive margins had a 100 % intervention rate. There were two false negative on IOFS. IOFS had a sensitivity of 85.17 % with a specificity of 100 % and a negative predictive value of 99.16 %. Specimens with a positive IOFS were lower rectal (P < 0.05), poorly differentiated and post LCRT locally advanced tumours.

IOFS to confirm negative DRM is recommended in lower rectal tumours irrespective of DSM. It can be considered for locally advanced post LCRT poorly differentiated mid rectal tumours and avoided for upper rectal tumours.