Abstract: Objective:To investigate the effects of the number of harvested lymph nodes in neoadjuvant chemoradiotherapy (nCRT) combined with surgery on prognosis of middlelow rectal cancer.
Methods:The retrospective casecontrol study was conducted. The clinicopathological data of 373 patients with middlelow rectal cancer who underwent nCRT combined with surgery in the Fujian Medical University Union Hospital from January 2009 to December 2013 were collected. There were 241 males and 132 females, aged from 26 to 81 years, with the age of (55±11)years. Observation indicators: (1) treatment situations; (2) follow-up and survival; (3) influencing factors for the number of harvested lymph nodes; (4) prognostic analysis of the different number of harvested lymph nodes as cutoff for grouping; (5) stratified analysis. Follow-up using telephone interview and outpatient examination was performed to detect postoperative survival of patients once every three months within postoperative 2 years and once every 6 months during the postoperative third year up to March 2016. The endpoint of follow-up was tumor recurrence, retastasis or death. Measurement data with normal distribution were represented as Mean±SD, and comparison between groups was done using the independent sample t test. Measurement data with skewed distribution were represented as M (range), and comparison between groups was done using the KruskalWallis H test. Count data was described as absolute numbers. Univariate and multivariate analyses were done by the multiple linear regression model. Survival rate was calculated by the Kaplan-Meier method, and Logrank test was used for survival analysis.
Results:(1) Treatment situations: 373 patients underwent nCRT combined with surgery, including 329 combined with sphinctersparing rectal resection and 44 combined with abdominoperineal rectal resection. The number of harvested lymph nodes was 12 ± 6 in 373 patients. There were 185 patients with the number of harvested lymph nodes <12 and 188 with the number of harvested lymph nodes ≥12. (2) Follow-up and survival: 373 patients were followed up for 5-77 months, with a median follow-up time of 43 months. During the follow-up, the 1, 3, 5year diseasefree survival rates were respectively 90.4%, 76.3%, and 67.5% in the 373 patients. (3) Influencing factors for the number of harvested lymph nodes: univariate analysis showed that distance between the tumor and anal verge, tumor diameter, tumor pathological N staging, and regression grade of rectal cancer were associated factors for the number of harvested lymph nodes (t=3.156, 2.992, x²=8.183, 10.839, P<0.05). Multivariate analysis showed that distance between the tumor and anal verge, regression grade of rectal cancer, and tumor pathological N staging were independent factors for the number of harvested lymph nodes (t=3.308, 2.690, 2.584, 95% confidence interval: 0.808-3.180, 0.446-2.873, 0.332-2.448, P<0.05). (4) Prognostic analysis of the different number of harvested lymph nodes as cutoff for grouping: with the number of harvested lymph nodes of 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and 16 as cutoff for grouping, there was no significant difference in the 3year diseasefree survival rate, cumulative local recurrence rate, and cumulative distant metastasis rate between <6 group and ≥6 group, between <7 group and ≥7 group, between<8 group and ≥8 group, between <9 group and ≥9 group, between <10 group and ≥10 group, between <11 group and ≥11 group, between <12 group and ≥12 group, between <13 group and ≥13 group, between <14 group and ≥14 group, between <15 group and ≥15 group, between <16 group and ≥16 group, respectively (P>0.05). (5) Stratified analysis: with the number of harvested lymph nodes of 7, 8, 9, and 10 as cutoff for grouping in 45 of 373 patients with Ⅱ-Ⅲ regression grade of rectal cancer and negative lymph nodes (N0 staging), there was no significant difference in the 3year diseasefree survival rate between <7 group and ≥7 group, between <8 group and ≥8 group, between <9 group and ≥9 group, between<10 group and ≥10 group, respetively (x²=3.946, 5.346, 6.375, 4.297, P<0.05).
Conclusions:The number of lymph nodes as 12 is not the independent factor for prognosis of patients with middlelow rectal cancer after nCRT combined with surgery. The number of harvested lymph nodes as 7 to 10 is the important factor for evaluating the prognosis of middlelow rectal cancer patients with Ⅱ-Ⅲ regression grade of rectal cancer and negative lymph nodes after nCRT combined with surgery.