This trial aims to assess safety and efficacy of three-row circular staplers compared to two-row surgical stapllers in short-term and long-term perspective in patients with rectal cancer undergoing low anterior resection with stapled colorectal anastomosis. All the patients will undergo a low anterior resection. In a half of patients a colorectal anastomosis will be created with a three-row surgical circular stapler. In another half of patients a colorectal anastomosis will be created with a two-row surgical circular stapler.

A low anterior resection for rectal cancer in most cases results in creating a colorectal anastomosis with a surgical circular stapler device. Using a disposable circular stapler with two rows of staples is standard of care nowadays. Colorectal anastomosis dehiscence and subsequent anastomotic leak in postoperative period happens in 5-25% of cases and is a major and life-threatening complication. Thus different improvements to the procedure of creating a colorectal anastomosis are being proposed. One of them is utilizing a three-row instead of a two-row surgical circular stapler.

A three-row surgical stapler has recently been registered and approved for clinical use in Russia. The primary purpose of this study is to find out the rate of colorectal anastomosis leakage when using a three-row circular stapler and to demonstrate that it is at least not bigger than the rate of colorectal anastomosis leakage when using a two-row circular stapler.

Inclusion Criteria:

1. Provision of signed and dated informed consent form
2. Stated consent to comply with all study procedures and availability for the duration of the study
3. Male or female
4. For females of reproductive potential: not pregnant at the time of screening
5. For males of reproductive potential: use of condoms or other methods to ensure effective contraception with partner
6. Histologically proven primary rectal adenocarcinoma located within 5 to 15 cm from anal verge not involving internal and/or external sphincter muscle

Non-inclusion Criteria:

1. Current use of antiplatelet drugs, acetylsalicylic acid or anticoagulants within 7 days prior to intervention
2. Unresectable tumour, inability to perform a TME with colorectal anastomosis, inability to complete R0 resection or presence of T4b tumour necessitating a multi-organ resection
3. Inability to save the left colic artery
4. Diameter of rectal lumen is unable to contain the working part of the stapler
5. Infection requiring antibiotic treatment within 30 days prior to intervention
6. Anal incontinence prior to surgery (Wexner Continence Grading Scale >=10)
7. Significant comorbidities - ASA > III

Exclusion criteria:

1. Patient lost for observation
2. Inability to complete all the trial procedures
3. Death due to causes unrelated to anastomotic leak in early postoperative period

8. Current smoker or tobacco use within <specify timeframe> 9. Patient wants to withdraw from the clinical trial