Does grade matter? Evaluation of histologic grade in patients with stage 1 non-small cell lung cancer using the...

In the United States, histologic grade in non-small cell lung cancer (NSCLC) is not part of the TNM stage classification. We hypothesize that histologic grade may impact prognosis.

The National Cancer Database (NCDB) for NSCLC was used to identify all pathological stage 1 cancer patients who underwent definitive surgery between 2013 and 2020. Three groups were created using histologic grade for both adenocarcinoma and squamous cell carcinoma: well-differentiated (G1), moderately differentiated (G2), and poorly/undifferentiated (G3).

The study cohort comprised 37,727 adenocarcinoma patients (10,784 G1, 18,647 G2, 8476 G3) and 17,697 squamous cell carcinoma patients (601 G1, 10,002 G2, 7904 G3) patients who underwent definitive surgical resection for stage 1 cancer. More patients in the G3 adenocarcinoma group had a larger tumor size (18 mm vs 20 mm vs 21 mm; P < .001). Overall survival was significantly better for the G1 group (log-rank P < .001) (G2 vs G1: HR, 1.51, P < .001; G3 vs G1: HR, 1.9, P < .001; G3 vs G2: HR, 1.26; P < .001). In the squamous cell carcinoma patients, characteristics were comparable across the 3 groups. Similar to the adenocarcinoma patients, tumor size was larger in the squamous cell carcinoma G3 group (20 mm vs 22 mm vs 24 mm; P < .001). Overall survival was not significantly different across the 3 squamous cell carcinoma groups (P < .001).

Histologic grade for adenocarcinoma has gained international attention with the new classification scheme according to the International Association for Study of Lung Cancer. Histologic grade, at least in adenocarcinoma, may provide an important prognostic indicator, and further work is needed to tailor treatment for those with high-grade tumors.