The Effect of Circumferential Tumor Location in Clinical Outcomes of Rectal Cancer Patients Treated With Total Mesorectal Excision

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Abstract
A positive circumferential resection margin is associated with a high risk of local recurrence and distant metastasis after total mesorectal excision for rectal cancer. The mesorectum is thinner anteriorly than posteriorly, and the risk of a positive resection margin may be higher for anterior than for posterior tumors. We sought to determine the effect of the tumor's position in the circumference of the rectum on the treatment and outcomes of rectal cancer patients treated by total mesorectal excision. We retrospectively analyzed 401 patients with rectal cancer staged by preoperative endorectal ultrasound and treated by sharp mesorectal excision with or without neoadjuvant therapy. Tumors were classified into four groups (anterior, posterior, lateral, and circumferential) according to the location of deepest point of penetration on endorectal ultrasound. Differences in recurrence and survival rates were analyzed with logistic regression analysis. Of the 401 tumors, 27 percent were anterior, 26 percent posterior, 32 percent lateral, and 15 percent circumferential. The groups did not differ in age, gender, tumor distance from the anal verge, or tumor grade. The ultrasound and pathology stages were more advanced in the circumferential group, and the proportion of uT4 tumors was higher in the anterior group. Circumferential and anterior tumors were more likely to receive preoperative adjuvant radiation. After an average follow-up of 44 months, 20 percent of patients had developed recurrence (13 percent distant, 6 percent local, and 1 percent distant and local). Recurrence was associated with advanced tumor stage, tumor proximity to the anal verge, and no preoperative adjuvant therapy. Early tumor stage and preoperative chemoradiation were associated with lower recurrence and improved survival. When tumor stage was controlled for, patients with poor or undifferentiated tumors and male patients with anterior tumors were shown to have a higher risk of recurrence or death. The estimated five-year disease-free survival for the entire group was 73 percent. Tumor stage is the main criterion to estimate prognosis in rectal cancer patients. The position of the tumor within the circumference of the rectum may provide valuable clinical information. Anterior tumors tend to be more advanced and, at least in male patients, has a higher risk of recurrence and death than tumors in other locations.