수술 전 항암방사선 치료를 받은 직장암 환자에서 측방 골반림프절 전이가 종양학적 결과에 미치는 영향

Abstract

Background : Lateral pelvic lymph node is known as main local recurrence site in rectal cancer even after preoperative chemoradiotherapy (PCRT). There have been increased in interest regarding the prognostic implication of lateral pelvic lymph node (LPLN) metastasis and role of lateral pelvic lymph node dissection in rectal cancer. However, evidences regarding prognostic impact and treatment of lateral pelvic lymph node metastasis (mLPLN) in patients with rectal cancer treated with PCRT are not enough. In this study, we evaluated the impact of mLPLN identified in imaging modality on oncologic outcomes and effect of lateral pelvic lymph node sampling (LPLNs) on prognosis in rectal cancer patients received PCRT. Methods : We identified 1535 patients who received PCRT and radical resection between January 2008 and December 2016 at Asan Medical center, Seoul, Korea. Patients who had pre/post PCRT pelvic MRI and/or abdominopelvic CT were included. mLPLN was defined as enlarged lymph node with short axis> 5mm in pre- and post- PCRT or radiologic malignant features including round, spiculated, ill-defined margin or heterogenous signal in MRI. Recurrence type was categorized as local recurrence (LR), distant recurrence (DR), and pelvic recurrence (PR). LR was defined as recurrence with clinical, radiologic, or endoscopic evidence of intraluminal tumor in adjacent to primary resection site, or tumor within the mesorectum or rectal wall after primary operation. PR was defined as recurrence in pelvic LN including common iliac, external iliac, internal iliac, and obturator LNs. PR was not included in both LR and DR. Distant lymph node not included in PR was categorized as DR. Association between mLPLN and disease-free survival (DFS), overall survival (OS), local recurrence free survival (LRFS), pelvic recurrence free survival (PRFS) was analyzed and risk factors associated with OS and DFS were also analyzed. In patients who had clinical mLPLN (+), influence of LPLNs was analyzed. Results : Of 1535 patients, 317(20.6%) before PCRT and 264(17.1%) after PCRT were identified with mLPLN (+) on MRI. The patients with pathologic complete & near complete regression and sphincter saving resection was more in pre-/and post- PCRT mLPLN (-) group than (+) groups (P < 0.001). LR, DR, and PR were higher in mLPLN (+) group than (-) group in both pre-PCRT (LR: 7.3% vs. 3.9%, DR: 26.5% vs. 18.7%, PR: 3.8% vs. 1.1%) and post-PCRT (LR: 12.1% vs. 4.3%, DR: 28.8% vs. 18.6%, PR: 5.3% vs. 0.9%). DFS, LRFS, PRFS and OS were higher in pre-/post-PCRT mLPLN (-) groups than (+) groups. Poor response to PCRT (moderate & minimal & no regression) was confirmed as risk factors of OS, DFS, LRFS, DRFS, and PRFS (OS; HR 1.37, P = 0.029, DFS; HR 1.36, P = 0.018, LRFS; HR 1.78, P = 0.062, DRFS; HR 1.33, P = 0.03, PRFS; HR 6.46, P = 0.013). Pre-PCRT mLPLN was associated with OS (HR 1.39, P = 0.042) and post-PCRT mLPLN was associated with DFS (HR 1.36, P = 0.048) and PRFS (HR 4.95, P = 0.002). In entire cohort, LPLNs was performed in 97 (6.3%) patients. Among patients who received LPLNs, mLPLN was pathologically confirmed in 28 (28.8%) patients and there was no significant difference between patients who were not diagnosed with mLPLN pathologically in OR and DR. However, PR was significantly higher in patients with pathologically confirmed mLPLN (16.1% vs. 3.0%). LPLNs group showed higher 5-year LRFS rate and 5-year OS rate than no LPLNs group in both pre-/and post-PCRT mLPLN (+) groups, but it was not statistically significant. Conclusion : According to results of this study, patients with pre-/post-PCRT mLPLN (+) had higher LR, PR, DR rate and worse OS, DFS, LRFS, PRFS rate and good primary tumor response to PCRT was associated with OS, DFS, LRFS, DRFS, and PRFS. There were no significant differences in OS and LRFS between LPLNs and no LPLNs group, and even no LPLNs group showed higher 5-year DFS and PRFS. We have to decide to perform lateral pelvic lymph node dissection carefully for this reason considering both advantages and disadvantages. LPLNs of suspicious mLPLN was not associated with oncologic benefit in this cohort. Impact of extensive LPLN dissection on oncologic outcomes need to be evaluated in further study and decision of LPLN sampling or dissection has to be based on its oncologic benefit as well as prognostic implication of mLPLN.