P1.18-24 Neoadjuvant Therapy versus Upfront Surgery for NSCLC Patients with Clinically Suspected Subaortic or Paraaortic Lymph Nodes

Subaortic lymph nodes (#LN5) and para-aortic lymph nodes (#LN6) cannot be accessed by routine mediastinoscopy and E(B)US-FNA but need additional invasive surgical staging methods such as VATS or anterior mediastinotomy. Therefore, a considerable number of patients with suspected #LN5 or #LN6 receive multimodal treatment or, upfront surgery based on imaging staging only. We investigated survival outcomes of each therapeutic strategy. An institutional lung cancer database of consecutive patients between 2007 and 2016 (N=134) was reviewed retrospectively. Eligible patients had pathologically confirmed non-small cell lung cancer with clinically suspected #LN5 or #LN6 involvement by CT or PET-CT without clinical or pathological evidence of other N2 station involvement. Excluded are those with involvement of other N2 stations, unexpected N2, low grade malignancy, and prior history of cancer. Patients in group 1 received neoadjuvant therapy followed by surgery (n=68) and those in group 2 underwent upfront surgery (n=66). Group 1 consisted of patients with clinically suspected (n=39, 57%), and biopsy-proven #LN5 or #LN6 (n=29, 43%) by VATS (n=19), anterior mediastinotomy (n=6), or EUS-FNA (n=4). They received preoperative chemoradiation (n=62, 91%) and the rest received chemotherapy (n=6, 9%). Nodal down-staging was occurred in 36 (53%) patients whereas persistent N2 in 32 (47%). On the contrary, group 2 consisted of patients with clinically suspected #LN5 or 6 (n=66). After surgery, 30 (45%) patients were confirmed to have pathologic N0 or N1. The rest 36 (55%) patients were confirmed pathologic N2, and 29 (81%) of them received adjuvant therapy: chemoradiation in 23, and chemotherapy in 6. Overall survival rate at 5-year (5YOS) were 50.5% in group 1 versus 58.9% in group 2 (p=0.55); recurrence-free survival at 5-year (5YRFS) was 42.2% versus 46.7% (p=0.98), respectively. In subgroup, the 5YOS were 44.6% in pathologic N2 in group 2, which were similar to persistent N2 (52.8%, p=0.6), down-staged (49.2%, p=0.89), or biopsy-proven N2 (57.8%, p=0.54) in group 1. The 5YRFS were 26.7% in pathologic N2 in group 2, which were similar to persistent N2 (30.3%, p=0.89) and biopsy-proven N2 (43.9%, p=0.15), but lower than down-staged (53%, p=0.03) in group 1. Upfront surgery or omission of invasive mediastinal staging for #LN5 or 6 may not compromise survival outcomes. Each therapeutic strategy is effective in terms of oncologic outcomes.