8500 Background: Neoadjuvant immune checkpoint inhibitors (ICIs) plus chemotherapy have a promising efficacy in resectable non-small-cell lung cancer (NSCLC), yet the period of neoadjuvant immunochemotherapy is undetermined. This phase II study compared the efficacy and safety of two cycles with three cycles of neoadjuvant sintilimab plus chemotherapy in resectable stage IB-IIIA NSCLC. Methods: This randomized, open-label phase II trial recruited patients aged 18 or older with histologically confirmed, treatment-naïve, American Joint Committee on Cancer-defined stage IB-IIIA, resectable NSCLC. Eligible patients were randomly assigned to two or three cycles of neoadjuvant treatment with intravenous sintilimab (200 mg) plus carboplatin (area under curve 5) and nab-paclitaxel (260mg/m2, for squamous) or pemetrexed (500mg/m2, for non-squamous) on day 1 of three-week cycle. After surgical resection, patients received totally four doses of perioperative immunochemotherapy, followed by one-ye