Objective  The characteristics of locoregional rectal cancer recurrences following total mesorectal excision (TME) were not clear previously. This study aimed to analyze and help determine the optimal radiotherapy clinical target volume.

  Methods  The clinical data of 134 patients who had recurrence and metastasis following TME without radiotherapy between January 2012 and November 2018 in our hospital were retrospectively analyzed. The Chi-square test was used to evaluate the relationship between lymph node metastasis and clinicopathological factors, such as the location of primary tumors and tumor stage. The correlations between different types of lymphatic drainage of rectal cancer were also tested.

  Results  In total, 134 patients were enrolled in this study. The median time to relapse was 15 months. The incidences of anastomotic, rectal and mesorectal, pelvic presacral space, abdominal presacral space, internal iliac node, external iliac node, obturator node, inguinal node, and ischiorectal fossa recurrences were 42.5% (57/134), 26.9% (36/134), 25.4% (34/134), 7.5% (10/134), 34.3% (46/134), 3.7% (5/134), 0.7% (1/134), 9.7% (13/134), and 8.2% (11/134), respectively. Compared with mid- lower rectal cancer, upper rectal cancer was more prone to metastasis in the abdominal presacral space (19.0% vs. 5.6%, P=0.028). Patients with inguinal lymph node metastasis were more likely to harbor external iliac node metastasis (23.1% vs. 1.7%, P=0.006).

  Conclusions  There is a great difference in the recurrence patterns between upper and mid-lower rectal cancer. As a result, the clinical target volumes of radiation therapy for upper and mid-lower rectal cancer should be defined separately. Optimizing the clinical target volume of radiotherapy will be of great value in the future.