Severance Hospital said Thursday that robotic partial excision that preserves anus for patients with locally advanced rectal cancer invading levator ani muscle showed improved bowel function, prognosis, and survival and recurrence rates.

A research team, led by Professors Kim Nam-kyu, Yang Seung-yoon, and Cho Min-soo of Severance Hospital’s Yonsei Cancer Center, followed up patients’ bowel function for six months and a year after receiving the robotic partial excision of the levator ani muscle (PELM).

The research team used Memorial Sloan Kettering Cancer Center Bowel Function Instrument (MSKCC BFI) and Wexner score for evaluating the condition.

MSKCC BFI is a measure designed for examining bowel function after having a sphincter-preserving surgery for rectal cancer. Patients initially scored 64.9 points in the first test taken in the sixth month, and the figure rose to 68.3 after another six months.

In the Wexner test, which shows better fecal incontinence with lower scores, patients scored 11 on average in the sixth month. Still, the number decreased by 0.3 points to 10.7 after one year.

The study also showed satisfying treatment outcomes. Patients recorded a 95 percent three-year survival rate, 72.4 percent three-year disease-free survival rate, and 14.4 percent local recurrence rate during a median follow-up period of 44.1 months.

Professor Kim developed the surgical method in 2011 to partially remove the levator ani muscle and sphincter when lower middle rectal cancer invaded the levator ani muscle.

The research team followed up 23 patients who underwent PELM operation from 2011 to 2019 and followed up the bowel function and treatment responses for 44.1 months.

The average age of the patients was 55.3 years, the youngest among rectal cancer patients most prevalent among those in their 60s. Doctors reduced the tumor size to between 1.7 and 3.3 centimeters with chemotherapy before the operation.

“The biggest concern of rectal cancer patients is for losing their anal function after surgery and have a permanent stoma,” Kim said. “We developed a new surgical method that can preserve the anus even in rectal cancer that partially invaded the levator ani muscle and confirmed the safety through long-term follow-up.”

The study results were published in the latest issue of the International Journal of Medical Robotics and Computer Assisted Surgery.