Abstract
The evolution over the past 20 years of anal preservation in rectal cancer surgery has been truly remarkable. Intersphincteric resection (ISR) reported by Schiessel in 1994 in Australia has been shown to enable anal preservation even for cancers quite close to the anus. In Japan, ISR via the detachment of the anal canal between the internal and external sphincters and excision of the internal sphincter first began to be practiced in the latter half of 1990. A multicenter Phase II trial of ISR in Japan suggested that 70% of the cases had relatively good function with less than 10 points of Wexner score but around 10% had severe incontinence that would not be improved for long term. The primary end point of the clinical study, 3-year local recurrence rate, was 13.2% across the overall cohort (T1, 0%; T2, 6.9%; and T3, 21.6%). When ISR is performed on T1/T2 rectal cancers, sufficient circumferential resection margin can be obtained even without preoperative chemoradiotherapy, and local recurrence rate was acceptably low. Based on these evidences, ISR is a currently important, standard treatment option among anal-preserving surgeries for T1/T2 low-lying rectal cancers. In Japan, a feasibility study (LapRC trial) of laparoscopic ISR on Stage 0 and Stage 1 low rectal cancer showed excellent outcomes. A prospective Phase II clinical trial targeting low rectal cancers within 5 cm from the anal verge (ultimate trial) is being performed and awaiting the results in near future.