Impact of neoadjuvant therapy on nodal harvest in clinical stage III rectal cancer: Establishing optimum cut‐offs by disease response

Abstract

IntroductionA minimum lymph node harvest (LNH) of 12 is the current standard for appropriate nodal staging in resectable rectal cancer. However, the rise of neoadjuvant chemoradiation (NCRT) and total neoadjuvant therapy (TNT) has been associated with decreasing number of LNH. We hypothesize that as tumor response to neoadjuvant therapy increases, the optimum for LNH to achieve appropriate nodal staging should decrease.MethodsPatients with clinical stage III rectal adenocarcinoma who underwent NCRT/TNT followed by resection were identified from the National Cancer Database. A JoinPoint regression analysis was used to determine the LNH for each tumor regression grade (TRG) category beyond which the rate of positive nodes does not significantly change.ResultsThirteen thousand four hundred and twenty‐six patients met inclusion criteria. Of these, 2406 (17.9%) achieved TRG 0 or ypT0 and 8210 (61.2%) achieved ypN0. Collectively, 2043 patients (15.2%) were reported to have a pathologic complete response (ypT0 ypN0). Positive pathologic nodes were found in 15%, 23%, 31%, 54%, and 53% as ypT stage increased from ypT0 to ypT4, respectively. Similarly, ypN+ rates were 15%, 36%, 41%, and 55% in TRG 0–3. No JoinPoint was identified for TRG 0, whereas inflection points were found at 6–10 nodes for TRG1 (p = 0.002) and TRG 2 (p = 0.016), and at 11–15 nodes for TRG 3.ConclusionThe benchmark of retrieving 12 nodes in resectable stage III rectal cancer is not consistently achieved after NCRT/TNT. We demonstrate that the LNH requirement to establish accurate pathologic nodal staging can vary depending on the tumor response to neoadjuvant therapies.

Impact of Lymph Node Retrieval on Prognosis in Elderly and Non-Elderly Patients with T3-4 Stage Rectal Cancer Following Neoadjuvant Therapy

“…Chase J Wehrle and colleagues believe that the standard of detecting 12 lymph nodes after neoadjuvant chemoradiation (nCRT) and total neoadjuvant therapy (TNT) is not uniform in resectable stage III rectal cancer. The LNH requirements for pathological lymph node staging may vary depending on the tumor's response to neoadjuvant treatment [32] . Matthew D Hall and others propose that at least 8 lymph nodes should be examined in rectal cancer patients receiving nCRT, and point out that 8 lymph nodes represent the threshold for adequate lymph node clearance after nCRT [33] .…”