Effect of preoperative therapy on surgical shrinkage in rectal cancer

Background. The possibility of performing a surgical margin of less than 2 cm without increasing the risk of recurrence is an important problem. Most studies were conducted on a specimen examined after resection and formalin fixation without taking into account tissue contraction – surgical shrinkage. The effect of neoadjuvant treatment combinations on surgical shrinkage is also not determined.
Aim. To study the effect of shrinkage of the distal margin of resection of the rectum in colorectal cancer after formalin fixation, as well as the effect of preoperative therapy on the shrinkage.
Materials and methods. In total, 183 patients with histologically verified rectal and sigmoid colon cancer (adenocarcinoma G1–3) who underwent surgical treatment were prospectively analyzed. The distance between the lower pole of the tumor and the distal resection margin was measured immediately after excision. Then, this parameter was measured after fixation of the specimen in 10 % formalin solution.
Results. Median rectal shrinkage after formalin fixation of the specimen was 22.46 % in the surgical treatment group and 19.27 % in the radiation therapy group. In 101 cases, rectal shrinkage was more than 20 %. A statistically significant difference was found in the incidence of surgical shrinkage more than 20 % in the group of patients who did not receive radiotherapy (p = 0.045).
No statistically significant relationship was found between surgical shrinkage and gender (p = 0.135), tumor location (p = 0.082), or tumor advancement (p = 0.355). There was also no statistical significance between surgical shrinkage and the type of surgery (p = 0.225).
Conclusion. Measurement of the distal resection margin under different conditions influences the assessment of oncologic clearance when interpreting pathological findings and determining treatment outcomes. Radiotherapy is associated with higher probability of a lower degree of rectal shrinkage, which may be of significant importance in surgical treatment.

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