Table 2.

Association between the number of dissected lymph nodes and recurrence-free survival according to piece-wise regression models

Model	Recurrence-free survival
	HR (95%CI)	P value a
One-line (non-segmented)	0.98 (0.95, 1.01)	0.236
Segmented regression
Fewer than 9 nodes	0.77 (0.67, 0.87)	< 0.001
At least 9 nodes	1.01 (0.97, 1.04)	0.653
P in log-likelihood ratio test	0.001

^a Adjusted for age, sex, age-adjusted Charlson Comorbidity Index, surgical year, tumor site, family history of malignancy, histopathological subtype, spread through air space, pT, pN and postoperative adjuvant therapy

CI, confidence interval; HR, hazard ratio