Randomized Crossover Study of the Efficacy of Sacral Neuromodulation (SNM) With InterStimTM for Bowel Dysfunction Following Surgery for Rectal Cancers With Sphincter Preservation

This is a single-blind randomized crossover study. After providing written informed consent, eligible patients will undergo an initial stimulation procedure with a temporary lead (Step 1 Wire Stimulation). The simulation is performed to determine efficacy of the device before a permanent implant is placed. This stimulation takes place over a period of 7-14 days (+/-3 days). Because this procedure is done in the OR, this window of time allows for optimization of the device and coordination of operating room schedules. This is the time period that has been used in prior trials. Typically bowel improvement has been seen relatively quickly, so the range should not affect our assessment of BFI.

After the Wire Implantation has occurred, patients will be evaluated over the next 7-14 days (+/- 3 days) and will complete the BFI questionnaire. If BFI improvement is < than or = to 4 points the wire will be removed in the operating room, the patient will be offered standard of care, and the patient will no longer be part of the study. Based on our prior data, we would like to give as many patients as possible the opportunity for enrollment and as a result we have chosen a 4 point BFI change as minimum criteria for response. Our group has seen that a change in the BFI around 5-6 is clinically significant, but we will lower this threshold slightly. If a patient's BFI improves by ≥ 4 points, the patient will proceed to the randomized phase (Step 2-Implantation) of the study.

Patients who proceed to Step 2- Implantation, they will return to the operating room for the implantation of the permanent device. While in the operating room they will be randomly assigned to either having the device stimulation on (Group A) or device stimulation off (Group B) for first 4 weeks (+/-3 days). Patients will return to clinic 2 weeks later to cross over to the other arm (Step 3-Crossover) and the device stimulation will be set to on or off. Patients will come back to clinic within 7 days (+/- 7 days) after Crossover for device check and optimization.