Patients
From January 2000 to December 2012, a retrospective analysis was conducted of 302 non-metastasis consecutive diabetic patients with GC who underwent D2 lymphadenectomy, at the department of gastrointestinal surgery, Fujian Cancer Hospital & Fujian Medical University Cancer Hospital. All of the patients were diagnosed with stage pT1-4bN0-3bM0 GC according to the 7th edition of the TNM classifcation[23]. Data from these patients were entered into a prospectively maintained database.
The inclusion criteria were as follows: 1. non-metastasis GC; 2. adenocarcinoma conformed by histopathology; 3. physical fitness suitable for surgery; 4. D2 lymphadenectomy; and 5. no prior history of any type of adjunctive therapy; 6. preprandial glucose> 7.1 mmo/L.
The exclusion criteria were as follows: 1. older than 80 years of age; 2. previous or concomitant other cancer; 3. previous or concomitant gastrectomy for benign disease; 4. previous chemotherapy or radiotherapy; 5. esophageal involvement; or 6. distant metastatic disease; 7.non-curative resection; 8. multiple primary malignancies; 9. remnant GC; 10. 15 retrieved lymph nodes, and 11. mortality within 30 days after surgery.
This data set included patient demographics (age and sex), pathologic characteristics (depth of invasion, number of metastatic lymph nodes, and number of examined lymph nodes), and follow-up data (follow-up duration and survival). The depth of invasion was categorized as mucosa, submucosa, proper muscle, subserosa, serosa, or adjacent organ invasion. The number of metastatic lymph nodes was categorized according to the node grouping of the seventh TNM classification[23]. Adjuvant chemotherapy was categorized as received or not received. Follow-up data were collected from hospital records for patients who were lost to follow-up. The follow-up duration was measured from the time of surgery to the last follow-up date, and information regarding the survival status at the last follow-up was collected.
All of the above patients were followed up by telephone interviews. The last follow-up was 1 January 2017. The logical and follow-up findings were collected and recorded in the database. All subjects gave written informed consent to the study protocol, which was approved by the Ethical Committees of Fujian Cancer Hospital & Fujian Medical University Cancer Hospital.
Surgery
According to the 7th edition NCCN guidelines[24], surgery with lymph node (LN) dissection is the primary treatment option for medically fit patients with resectable T1-4b, any N tumors. All patients in the study underwent standard total or distal gastrectomy, depending on the location and macroscopic appearance of the primary tumor (Table 1). The strategy for LN dissections was determined using a standardized technique according to the guidelines of the 2010 Japanese Classification of Gastric Cancer and Gastric Cancer Treatment Guidelines edited by the Japanese Gastric Cancer Association[25].
Clinicopathological characteristics
The clinicopathological findings, including depth of tumor invasion and LN metastases, were utilized to stage tumors according to the 7th edition NCCN guidelines[24]. LNs were dissected and described according to the Japanese Classification of Gastric Carcinoma[25], which was also used to classify the location, histological type, and lymphatic invasion of tumors.
Statistical analysis
The associations between N category and clinic-pathological features were analyzed using Chi-square test. Risk factors for survival outcomes were identified by Kaplan-Meier analysis and Cox regression models. Only variables that were significance in univariate analysis were included in the multivariate model. The X-tile program(http://www.tissuearray.org/rimmlab/) which identified the cut-off with the minimum P values from log-rank χ2 statistics was used to divide patients into high and low risk subsets, as previously described[26]. The primary endpoints of this study was cause specific survival (CSS). Deaths attributed to gastric cancer were treated as events, while other reasons caused deaths or survivors were defined as censored events. All analyses were performed with survival package of R(Version 3.2.1) and SPSS(Version 22.0). Prism 5 for Windows(Version 5.01, GraphPad Software) was used to draft the figure of Kaplan-Meier curve. Difference with P-value <0.05 was regarded as statistically significant.