title: Clinical Significance of Extramural Tumor Deposits in the Lateral Pelvic Lymph Node Area in Low Rectal Cancer: A Retrospective Study at Two Institutions.
abstract: BACKGROUND
  The presence of extramural tumor deposits without lymph node structure (EX) is an important prognostic factor for patients with colorectal cancer. However, the clinical significance of EX in the lateral pelvic lymph node area (LP-EX) remains unclear. This study aimed to determine the prognostic implications of LP-EX for patients with low rectal cancer.
  
  
  METHODS
  This retrospective study involved 172 consecutive patients with stage 2 or 3 low rectal cancer who underwent curative surgery including lateral pelvic lymph node (LPLN) dissection. The patients were classified into the following three groups according to the metastatic status of the LPLN area: patients without metastasis (no-LP-M group), patients with lymph node metastasis (LP-LNM group), and patients with EX (LP-EX group). Potential prognostic factors of overall survival (OS) and relapse-free survival (RFS) were identified in uni- and multivariate analyses.
  
  
  RESULTS
  Classification assigned 131 patients (76 %) to the no-LP-M group, 27 patients (16 %) to the LP-LNM group, and 14 patients (8 %) to the LP-EX group. The 5-year OS rate was 80.3 % in the no-LP-M group, 61.1 % in the LP-LNM group, and 34.9 % in the LP-EX group (P < 0.001). The corresponding 5-year RFS rates were 62.2, 33.8, and 14.3 %, respectively (P < 0.001). A multivariate Cox proportional hazards regression analysis showed that the presence of LP-EX was an independent prognostic factor for OS (P = 0.006) and RFS (P = 0.001).
  
  
  CONCLUSIONS
  The LP-EX classification is a useful pathologic parameter that can be used to stratify patients with metastasis in the LPLN area.
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Ryoma
authors.initials: R
authors.lastname: Yagi
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan. shimaday@med.niigata-u.ac.jp.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Shimada
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kameyama
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Tajima
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Takuma
authors.initials: T
authors.lastname: Okamura
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Sakata
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Department of Digestive and General Surgery, Uonuma Institute of Community Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Kosugi
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Wakai
authors.affiliation: Department of Surgery, Niigata Cancer Center Hospital, Niigata, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nogami
authors.affiliation: Department of Surgery, Niigata Cancer Center Hospital, Niigata, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Maruyama
authors.affiliation: Department of Surgery, Niigata Cancer Center Hospital, Niigata, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Takii
authors.affiliation: Department of Pathology, Niigata Cancer Center Hospital, Niigata, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawasaki
authors.affiliation: Department of Pathology, Niigata Cancer Center Hospital, Niigata, Japan.
authors.forename: Kei-Ichi
authors.initials: KI
authors.lastname: Honma