Living on the Edge: Role of Adjuvant Therapy After Resection of Primary Lung Cancer Within 2 Millimeters of a T-Stage Cutoff.

Objectives: We evaluated the use of systemic therapy and overall survival in patients with resected non-small cell lung cancer (NSCLC) whose pathologic tumor size was within 2mm of a T-stage cutoff.

Methods: Retrospective cohort study using the National Cancer Database of patients who underwent resection of tumors within 2mm of the T1c/T2a, T2a/T2b, and T2b/T3 T-stage cutoffs. Patients with nodal involvement or whose T-stage was based on pathologic features other than tumor size were excluded. A multistate model compared the primary outcomes of systemic therapy and overall survival.

Results: From the NCDB, 18,490 patients were identified: 9,966 at the T1c/T2a cutoff, 5,593 at the T2a/T2b cutoff, and 2,931 at the T2b/T3 cutoff. Peaks in tumor size distribution occurred at 5mm intervals. Based on an expected normalized curve, 2,050 patients (11.1%) may have been under-staged. Use of systemic therapy was higher among patients with larger tumors at the T1c/T2a cutoff (7.1% vs. 8.9%; p<0.001), the T2a/T2b cutoff (20.0% vs. 25.5%; p<0.001), and the T2b/T3 cutoff (31.2% vs. 41.8%; p<0.001). In a multistate model, mortality was higher above the T1c/T2a cutoff (Hazard Ratio [HR] 1.10; p=0.01), T2a/T2b cutoff (HR 1.17; p<0.01), and T2b/T3 cutoff (HR 1.13; p=0.03). In patients who received systemic therapy, this trend was eliminated (HR 1.24; p=0.14, HR 0.79; p=0.07, and HR 1.23; p=0.09, respectively).

Conclusions: Rounding of tumor size for pathologic staging is common. While seemingly trivial, rounding may downstage patients and is associated with decreased rates of adjuvant therapy use and potentially worse overall survival.