LAUSR

8519 Background: The role of adjuvant chemotherapy (AC) in stage IB (pT2aN0) and IIA (pT2bN0) non-small cell lung cancer (NSCLC) is currently unclear. Existing guideline recommendations are inconsistent, ranging from all tumors >4 cm, to any patient with “high-risk features” (visceral pleural invasion (VPI), lymphovascular invasion (LVI), high grade, or sublobar resection). We used the National Cancer Data Base (NCDB) to clarify the role of AC in pT2N0 patients. Methods: The NCDB was queried for treatment-naïve, post-R0 resection, pT2N0 (AJCC 8th edition) NSCLC patients between 2010 & 2014. Patients treated with single-agent AC were excluded. Survival was calculated from 30 days after surgery to minimize immortal time bias. Multivariable Cox proportional hazards regression was used to estimate the association between AC and survival across tumor sizes (T2a: 3-4 cm and T2b: 4-5 cm to reflect guideline stratifications) and risk features. Results: Of the 10,127 patients identified, 1,856 (18%) received multi-agent AC. AC patients tended to be younger (median age 64 vs 70 yrs, p<0.001), privately insured (40% vs 24%, p<0.001), treated at a non-academic center (71% vs 66%, p<0.001), and comorbidities-free (53% vs 48%, p<0.001). In T2a patients (N=6,699), AC was not significantly associated with a mortality reduction, regardless of the presence of any high-risk features. In T2b patients (N=3,428), AC (N=931, 27%) was associated with a lower mortality (HR 0.77, 95% CI 0.65-0.9, p=0.001). However, in the absence of any high-risk features (N=1414, 41% of the 4-5 cm cohort), AC was not significantly associated with survival benefit (Table). Conclusions: The presence of high-risk features does not appear to support the guideline recommendations regarding the use of AC in stage IB patients with 3-4 cm tumors. On the other hand, the benefit of AC for 4-5 cm tumors may be limited to patients with at least one high-risk feature. [Table: see text]