Lateral lymph node metastasis is a major cause of locoregional recurrence in rectal cancer treated with preoperative chemoradiotherapy and curative resection

Background: In rectal cancer patients treated with preoperative chemoradiotherapy (CRT) and curative resection, we evaluated the effect of clinical parameters on lateral pelvic recurrence and made an attempt to identify a risk factor for lateral pelvic recurrence. Methods: The study involved 366 patients who underwent preoperative CRT and curative resection between October 2001 and December 2005. Clinical parameters such as gender, age, tumor size, histologic type, cT and cN classification, ypT and ypN classification, circumferential resection margin, tumor regression grade, chemotherapeutic regimen, and lateral lymph node size were analyzed to identify risk factors associated with lateral pelvic recurrence. Results: Of the 366 patients, 29 patients (7.9%) had locoregional recurrence: 6 (20.7%) with central pelvic recurrence and 24 (82.7%) had lateral pelvic recurrence, of which 1 had simultaneous central and lateral pelvic recurrence. Multivariate analysis showed that ypN classification and lateral lymph node size were significantly associated with lateral pelvic recurrence (P < .001). Of 250 ypN0 patients, lateral pelvic recurrence developed in 1.4%, 2.9%, and 50% of patients with lateral lymph node sizes of < 5, 5-9.9, and >= 10 mm, respectively (P < .001). Of 116 ypN+ patients, lateral pelvic recurrence developed in 4.3%, 35.7%, and 87.5% of patients with lateral lymph node sizes of < 5, 5-9.9, and >= 10 mm, respectively (P < .001). Conclusions: In our study, lateral pelvic recurrence was a major cause of locoregional recurrence, and ypN+ and lateral lymph node size were risk factors for lateral pelvic recurrence.