Rectal cancer is a common problem worldwide and the standard potentially curative treatment for locally advanced disease includes radical surgery appreciating oncological principals. Sphincter-saving procedures have been practiced in order to prevent a permanent stoma; however, patients underwent low anterior resection may suffer from several problems including incontinence particularly if the initial tumor is located too close to the anal canal. The actual frequency of incontinence is still unknown because of wide variation rates in several reports ranging between 0 to 80%; and may be a long-term problem since a series has presented an incidence of 36% 10 years after surgery.

Several mechanisms may cause incontinence after low anterior resection, thus several therapeutic instruments have been described considering the underlying reason. The most reasonable suspect is probably an injury to the sphincters at the time of surgery or secondary to preoperative radiation therapy, which is a commonly used modality in order to reduce local recurrence and increase the possibility of sphincter-saving procedures with the shrinkage of the tumor. Surgery and/or (chemo)radiation may not only generate sphincter injury, but also cause nerve damage and consequent denervation of the sphincters. Internal sphincters are responsible for resting pressure. Incontinence is more often and obvious if an intersphincteric resection with a hand-sewn coloanal anastomosis is attempted, since this procedure indicates the removal of internal sphincters. Several studies have revealed that up to 20% of patients have internal sphincter injuries after low anterior resection proven with endoanal ultrasound or manometer; and diminution in size of sphincters and decrease in resting pressure are correlated with incontinence grade. Mechanical anal sphincter injury may occur during the insertion of stapler; thus, incontinence may also be observed in patients with more proximally located tumors. The effect of radiation therapy on sphincter functions is also well-known, and a prospective randomized trial has shown that radiotherapy is significantly increasing incontinence rate. Another mechanism in incontinence may be related to the reduction of the capacity of neorectum, since descending colon, which is the reconstructing organ in most cases is narrower than rectum itself. Several reservoir techniques including coloplasty, colonic j-pouch and side-to-end anastomosis have been described in order to increase pooling volume of neorectum. Some other factors including decrease in sensitivity of anal canal and anal transitional zone, alteration in rectoanal inhibitory reflex, motility dysfunction of neorectum and incomplete evacuation may separately cause incontinence or increase the severity of symptoms. Instead of a sole origin, a combination of several reasons may be present at the same time making the problem more complex and the solution tougher. The treatment of incontinence is problematic, and not always able to increase quality of life. Biofeedback and rehabilitation therapies are harmless and easy to use; thus, generally selected as the initial treatment modalities, however may be effective in a small portion of patients. More complex treatment techniques including sacral nerve stimulation decrease the severity of symptoms, however the implantation of the device is a costly, staged procedure. Little is known about the effectiveness of other techniques such as injectable substances on incontinence observed after low anterior resection. Some patients may require fecal diversion in order to achieve a better quality of life.

Platelet Rich Plasma (PRP) is a thrombocyte enriched liquid, and it increases cell proliferation and collagen formation where it is injected. Platelets activate some growth factors, cytokines and other bioactive mediators, and consequently initiate and regulate wound-healing period. PRP has been used in several chronic diseases for initiating and fastening the reconstruction phase, particularly for the tendon, muscle, ligament and articular system related injuries and inflammatory situations. The effects of PRP on symptoms and healing rate in patients with lateral epicondylitis and its superiority over bupivacaine or steroid injections have been shown in cohort and prospective randomized trials. PRP is also tested for the treatment of perianal fistula. When PRP injection is combined with mucosal advancement flap procedure, it has been shown to decrease the recurrence rate. In an animal model, PRP injection into the gastrocnemius muscle has shown to increase the strength of the muscle healing. Although it has a potential, -to the best to our knowledge- there is no study evaluating the safety and effectiveness of PRP injection for incontinent patients after low anterior resection.

Methods:

This project is a single arm, cohort study evaluating the safety and effectiveness of PRP injection into the anal sphincter on incontinence and related quality of life in incontinent patients after low anterior resection for rectal cancer. All participating patients will be informed about the protocol and PRP application, and informed consent will be obtained. The study will be run at Department of General Surgery at Istanbul Medipol University Medical School (IMU) and be completed in 24 months. Local Ethical Committee has approved the protocol (protocol number: 66291034-29) and The Scientific and Technological Research Council of Turkey (TUBITAK) has granted the study (project number: 117s133). First patient accrual is planned to happen before August 2019. For the first year, only the patients who had their previous cancer operation at IMU will be included to the study, but in case of a shortage in number of patients by the end of August 2020, the inclusion of the patients who had their initial surgeries in other institutions will be permitted.

Local Ethical Committee and governors of TUBITAK will be free to monitor the trial progress at any time. Actual status of the study will be reported to TUBITAK for observation and for the continuity of grant imbursements annually (twice during the study period) and after the finalization of data analysis and publishing. Interim analysis will not be stated, since the design has not been classified as high risk.