Risk of Occult Lymph Node Metastasis in pT2 Rectal Cancer: a Nationwide Retrospective Analysis

Aims Advances in transanal surgical and endoscopic resection techniques have increased the use of local excision (LE) as a diagnostic and potentially organ-sparing approach for early-stage (cT1-2N0) rectal cancer (RC). For pT1 RC, total mesorectal excision (TME) can be omitted if histological risk factors for lymph node metastasis (LNM) and local recurrence are absent, regardless of submucosal invasion depth, as defined by the current Dutch CRC guideline. However, for pT2 RC, completion TME is recommended, irrespective of the presence of histological risk factors and despite the potentially varying associated risks for LNM. At present, little is known about the incidence and predictive value of histological risk factors in pT2 RC. This study aims to describe the association between histological risk factors and LNM rate in pT2 RC.

Methods All consecutive patients with pT2 RC from two large Dutch multicentre retrospective registries who were node-negative on preoperative imaging (cN0) and underwent surgery without neoadjuvant therapy between 2012 and 2020 were analysed. Treatment options included TME and LE followed by completion TME or active MRI surveillance for≥24 months, which was considered evidence of node-negative disease. The primary outcome was the rate of LNM in pT2 RC without the presence of histological risk factors available in the dataset (lymphovascular invasion (LVI) and poor differentiation (PD)). Secondary outcomes were the predictive value of PD and LVI in univariable and multivariable analyses corrected for age, sex and tumour distance from the anal verge.

Results In total, 339 patients with pT2 RC met the inclusion criteria (mean age 69 years, 64% male). The majority – 262 patients (77.3%) – underwent primary TME, while LE was performed in 77 (22.7%). Of these, 58 (75.3%) patients received completion TME, with the remainder undergoing active surveillance. The overall LNM rate in our cohort was 15.6% (53/339). In the 271 patients (79.9%) without both LVI and PD, the LNM rate was reduced to 12.5% (34/271). The presence of either LVI or PD alone resulted in LNM rates of 27.6% and 14.3%, respectively. When both LVI and PD were present, LNM occurred in 2 out of 3 cases. In our study, LVI was found to be the only independent predictor of LNM according to univariable and multivariable analyses (p=0.002; adjusted odds ratio 2.8, 95% CI 1.4-5.5).

Conclusions In this large retrospective cohort, the absence of LVI and PD was associated with a relatively low risk of LNM in patients with pT2 RC. This suggests the presence of a potential low-risk group of pT2 RC patients who may qualify for omission of completion TME. However, to accurately identify this group, a more detailed histological risk assessment including a wider range of potential histological risk factors such as tumour budding is warranted.

 

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Conflicts of interest

Authors do not have any conflict of interest to disclose.

Publikationsverlauf

Artikel online veröffentlicht:
15. April 2024