Effect of Tumor Location on Outcome After Laparoscopic Low Rectal Cancer Surgery: A Propensity Score Matching Analysis

Total neoadjuvant therapy for locally advanced rectal cancer: a three-group propensity score matched study

PURPOSE

Total neoadjuvant therapy (TNT) has emerged as a therapeutic approach for locally advanced rectal cancer (LARC). However, the optimal chemotherapy cycles within TNT remain uncertain. This study aimed to evaluate and compare the prognostic efficacy of varying cycles of chemotherapy during TNT for LARC.

METHODS

Patients diagnosed with LARC (T3-4N0M0/T1-4N1-2M0), who underwent TNT or chemoradiotherapy followed by total mesorectal excision (TME) between 2015 and 2020, were retrospective included. Patients were categorized into three groups based on their neoadjuvant strategy: CRT (long-course chemoradiotherapy), STNT (long-course CRT with one to three cycles of chemotherapy), and LTNT (long-course CRT with four or more cycles of chemotherapy). Propensity score matching (PSM) based on gender, age, body mass index, tumor distance from the anal verge, clinical T stage, clinical N stage, and mesorectal fascia status was employed to reduce confounding bias. Primary endpoints were disease-free survival (DFS) and metastasis-free survival (MFS).

RESULTS

The study comprised 372 patients, with 73 patients in each group after PSM. Compared with CRT, both STNT and LTNT demonstrated improved DFS (5-year rate: 59.7% vs. 77.8% vs. 76.5%, p = 0.027) and MFS (5-year rate: 65.1% vs. 81.3% vs. 81.4%, p = 0.030). There was no difference in DFS or MFS between STNT and LTNT. These favorable outcomes were consistent among subgroups defined by tumor distance from the anal verge ≥ 5 cm, clinical T3 stage, clinical N positive status, or involved mesorectal fascia.

CONCLUSION

Compared to CRT, both STNT and LTNT demonstrated improved DFS and MFS outcomes. Notably, survival outcomes were similar between STNT and LTNT, suggesting that chemotherapy cycles in TNT may not significantly impact survival.

A boundary-guided transformer for measuring distance from rectal tumor to anal verge on magnetic resonance images

Accurate measurement of the distance from the tumor's lowest boundary to the anal verge (DTAV) provides an important reference value for treatment of rectal cancer, but the standard measurement method (colonoscopy) causes substantial pain. Therefore, we propose a method for automatically measuring the DTAV on sagittal magnetic resonance (MR) images. We designed a boundary-guided transformer that can accurately segment the rectum and tumor. From the segmentation results, we estimated the DTAV by automatically extracting the anterior rectal wall from the tumor's lowest point to the anal verge and then calculating its physical length. Experiments were conducted on a rectal tumor MR imaging (MRI) dataset to evaluate the efficacy of our method. The results showed that our method outperformed surgeons with 6 years of experience (p < 0.001). Furthermore, by referring to our segmentation results, attending and resident surgeons could improve their measurement precision and efficiency.

Distinctive features of small vessels on the mesorectal and parietal pelvic fascia as important landmarks in guiding precise inter-fascial dissection for low rectal cancer

BACKGROUND

The confinement of the pelvis and the complexity of pelvic fascial anatomy still pose difficulties in achieving good quality surgery for rectal cancer. We aimed to introduce small vessels on the mesorectal fascia and the parietal pelvic fascia as novel landmarks to aid in the identification of the inter-fascial dissection plane. Besides, the perioperative, survival, and functional outcomes of this surgical technique were reported.

METHODS

We first described that small vessels running on the mesorectal fascia and the parietal pelvic fascia showed distinctive features, which included (1) small vessels on the parietal fascia took the same orientation as the ureter or the sympathetic and parasympathetic nerve; (2) small vessels on the mesorectal fascia were coursing cranially and medially on the anterolateral aspect, and medially and caudally on the posterolateral aspect; (3) small vessels on the mesorectal fascia became invisible at the interface between the pelvic wall and the mesorectal fascia. These features could be applied in fascial identification and separation. Then, we reported the outcomes of low rectal cancer surgery with small vessels-guided technique.

RESULTS

From 2013 to 2016, a consecutive series of 310 patients with low rectal cancer underwent laparoscopic total mesorectal excision with small vessels-guided technique. The positive rate of circumferential resection margin was 3.2%, and complete mesorectal excision was achieved in 97.8% (303/310) patients. The 3-year overall survival, disease-free survival, and local recurrence rates were 89.4%, 79.7%, and 2.6%, respectively. The urinary function was considered normal in 96.8% of patients, with a moderate dysfunction in 3.2% of patients. Besides, 29.5% of male patients occurred sexual function injury.

CONCLUSION

Distinctive features of small vessels on the parietal pelvic fascia and the mesorectal fascia can serve as novel and additive landmarks in guiding precise inter-fascial dissection for low rectal cancer.