Clinicopathological characteristics predict lymph node metastases in ypT0‐2 rectal cancer after chemoradiotherapy

Abstract

Aims Changes in rectal cancer treatment include increasing emphasis on organ preservation. Local excision after chemoradiotherapy (CRT) for rectal cancer with excellent clinical response reduces morbidity and mortality compared to total mesorectal excision, although residual lymph node metastases (LNM) may cause local recurrence. Our aim is to identify clinicopathological factors predicting the presence of residual LNM in rectal cancer patients with ypT0‐2 tumours after neoadjuvant CRT. These risk factors may help to select patients who can be spared radical surgery without compromising oncological outcomes. Methods and results Rectal cancer patients with ypT0‐2 tumours after CRT and radical resection from five centres treated between June 1999 and February 2012 were included. Histopathology was reviewed extensively. Clinicopathological characteristics and their association with residual LNM were investigated. Of 657 consecutive CRT‐treated rectal cancer patients 210 with ypT0‐2 disease were included. Residual nodal disease was found in 44 cases (21.0%). Independent predictors of LNM were clinical nodal involvement (cN+) [odds ratio (OR): 2.79, 95% confidence interval (CI): 1.04–7.48, P = 0.042], high‐grade histopathology assessed in the post‐CRT resection specimen (OR: 6.46, 95% CI: 1.23–34.02, P = 0.028) and residual tumour diameter (RTD) ≥10 mm (OR: 2.54, 95% CI: 1.06–6.09, P = 0.036). An algorithm combining these factors stratified patients adequately according to LNM risk, independently of ypT category. Conclusions Clinical nodal involvement, high‐grade histopathology and RTD ≥10 mm are strong and independent predictors of residual nodal disease in rectal cancer patients with ypT0‐2 tumours after CRT. Risk stratification based on these factors may help to identify patients suitable for organ preserving therapy and should be validated in appropriately selected populations.

Prevalence of nodal involvement in rectal cancer after chemoradiotherapy

“…Finally, although still controversial in early disease 37 , MRI has improved local staging, so patients with obvious lymph node metastases on imaging are not selected for organ preservation and undergo formal TME, which reduces the risk of nodal regrowth. In addition to ypT category, there are other histological parameters by which to identify patients at a higher risk of lymph node metastases who are less suitable for organ-preserving treatment, such as lymphatic or vascular invasion and differentiation grade 38,39 . As differentiation grade and other histopathological factors of the tumour were poorly recorded in this pooled data set, these factors could not be included in the analyses.…”

“…Because of missing data, not all patients could be included in all analyses. Additionally, some baseline and histopathological details were lacking, such as the presence of tumour deposits, extramural vascular invasion, completeness of resection, size and number of harvested and involved nodes, and size and exact location of residual tumour in the bowel wall; this information could be of help in interpreting the data 39,40,43 . Moreover, clinical staging was probably suboptimal (specifically for nodal status) as MRI was not used in most studies, which may have influenced the outcomes.…”

How to measure tumour response in rectal cancer? An explanation of discrepancies and suggestions for improvement

“…Moreover, in the neoadjuvant setting it no longer easy to predict lymph node status based on histological features. Only tumour grading in the post-treatment specimen, in combination with remaining tumour diameter and clinical assessment of the nodal status showed some predictive value [57].…”

Correlation between T stage and lymph node metastasis in rectal cancer treated with preoperative chemoradiotherapy

“… 27 , 28 In our study, the proportion of nodal metastasis in pathologic complete response after neoadjuvant CRT was 8.3% with a 5-year disease-free survival of 90.1%. Bosch et al 29 reported lymph node metastasis status in ypT0 patients at a rate of 17.4%, ypT1 patients at a 14.8% rate, ypT2 patients at a 25.8% rate, and ypT stage did not predict residual nodal status after neoadjuvant CRT. However, Pucciarelli et al 13 reported the percentage of lymph node metastasis in ypT0 at 1.8%, in ypT1 at 16.9%, in ypT2 at 37.8%, and in ypT3 at 37.8%, and ypT stage was a predictive factor for lymph node involvement.…”