HOUSTON – Transanal total mesorectal excision can consistently achieve good pathological results for obtaining specimens in rectal cancer, and overcome the shortcomings of the open and laparoscopic approaches to rectal cancer surgery, particularly in the distal part of the rectum where obtaining quality specimens can be technically challenging, researchers at the Hospital Clinic of Barcelona have found.
Reporting at the annual meeting of the Society of American Gastrointestinal and Endoscopic Surgeons, Jacqueline van Laarhoven, MD, PhD, said, “Pathologically, transanal total mesorectal excision [TME] provides good results on integrity of the mesorectum, negative circumferential and distal resection margins, and lymph nodes per specimen.” This study represents the first results of a relatively large, single-institution cohort, Dr. van Laarhoven said.
Dr. Jacqueline van Laarhoven
The study involved 187 patients with mid- or low-rectal cancer who had transanal TME from November 2011 to June 2016. Dr. van Laarhoven explained that obtaining high-quality specimens is an important prognostic factor for determining locoregional recurrence in rectal cancer. The study analyzed results of excised specimens in the mesorectum, circumferential and distal resected margins, and lymph nodes, and compared outcomes with those in two randomized clinical trials of both open and laparoscopic TME – the COLOR II (Lancet Oncol. 2013;14:210-8) and COREAN trials (Lancet Oncol. 2014;15:767-74) – where applicable.
In the Barcelona study population, 63.1% had tumors in the midrectum and 36.9% in the low rectum. Transanal TME yielded complete mesorectal quality in 95.7% of cases, almost-complete quality in 1.6% and incomplete in 1.1%, but comparison with COLOR II and COREAN trials was difficult because of differing inclusion criteria, Dr. van Laarhoven said.
Mean distal margin was 2.1 cm in midrectal cancer with a positive distal resection margin in 3.2%. In low-rectal cancer, the mean distal margin was 1.1 cm with a positive distal resection margin in 7.8%. Dr. van Laarhoven noted the overall circumferential resection margin (CRM) was 8.6% in this study, compared with 8.3% overall for the COREAN trial. As for COLOR II, the overall rate for positive CRM in mid- and low-rectal tumors was around 9%, Dr. van Laarhoven said, but in the open group the positive CRM was 3% in the midrectal excisions and 22% in low-rectal disease.
With regard to lymph nodes, the Barcelona study reported a median of 14 per specimen, with a range of 11 to 18, Dr. van Laarhoven said. However, in nonirradiated patients, the median was 15 per specimen. “This is consistent with the fact that neoadjuvant radiotherapy leads to a decrease in the lymph-node harvest,” she said. “These results are comparable to the COREAN and the COLOR II trials.”
Sixty-two percent of patients received neoadjuvant chemoradiotherapy, 3.2% received radiotherapy only, and 2.1% chemotherapy only.
On preoperative staging, 3.2% had T1 tumors, 20.3% T2, 67.9% T3, and 7.5% T4. The overall positive CRM (less than 1 mm) was 8.6% (including T4 tumors).
Postoperative pathological staging showed complete remission in 16% of patients, pT1 in 6.4%, pT2 in 28.9%, pT3 in 42.8%, pT4 in 2.7%, and pTis in 1.6%.
Dr. van Laarhoven commented, “As the quality of the surgical treatment is a surrogate marker for survival, transanal TME can be regarded as an oncologically safe method to treat patients with rectal cancer.”
Dr. van Laarhoven reported having no financial disclosures.