Tumour stage and preoperative chemoradiotherapy influence the lymph node yield in stages I-III rectal cancer: results from a prospective nationwide cohort study.

Aim: The study aimed to determine whether the lymph node yield (LNY) in rectal cancer is influenced by patient-related and histopathological factors and the use of preoperative chemoradiotherapy (CRT).

Method: An analysis was carried out of the LNY in a nationwide Danish cohort of 7950 patients, treated by curative resection of Stage I-III rectal cancer during the period 2001-2011. The impact of year of diagnosis, age, gender, pathological stage of the tumour (pT-stage) and preoperative CRT on LNY was analysed.

Results: Twenty-nine per cent of the patients received preoperative CRT. The median LNY was 13 [interquartile range (IQR): 8-19]. A total of 43.4% of the patients had an LNY of < 12. The median LNY increased from 8 (IQR: 5-12) to 20 (IQR: 13-28) LNs over the years of the study period (P < 0.0001). Gender and body mass index (BMI) had no impact on the median LNY. Age had a minor impact, with a range of 12 (IQR: 8-18) to 13 (IQR: 9-20) (P < 0.0001). The LNY ranged from 9 (IQR: 6-14) to 16 (IQR: 10-26), according to pT-stage (pT0-pT4) (P < 0.0001). Median LNY, according to preoperative CRT or no preoperative CRT, was 10 (IQR: 6-16) and 14 (IQR: 8-18), respectively (P < 0.0001). The percentages of patients with an LNY of < 12, according to preoperative CRT or no preoperative CRT, were 58.7% and 37.1%, respectively (P < 0.0001).

Conclusion: An increase in the LNY over the period of the study was observed, probably reflecting improved quality of surgery and histopathology. A minor significant reduction of LNY was found with increasing age of the patient. LNY was significantly related to pT-stage and to the use of preoperative chemoradiotherapy. For these reasons the minimum harvest of 12 LNs as a surrogate marker for the oncological quality of surgery should be questioned.