Nonsmall Cell Lung Cancer Stage III

This is a multicenter, phase 2 non-randomized study to investigate the clinical feasibility and therapeutic efficacy of employing a MDT-based strategy in unresectable stage III ALK positive NSCLC following neoadjuvant alectinib in combination with platinum-based chemotherapy. Participants in this study must not have received any previous systemic anticancer therapy before enrollment. The study will consist of a 42-day screening period, a neoadjuvant treatment period, a local radical treatment period, a post-local treatment period, a safety follow-up visit occurring 28 days after the final dose of alectinib, and a survival follow-up period. In the neoadjuvant treatment period, participants will be provided with alectinib (600mg PO BID for 3 cycles) plus platinum-based chemotherapy for a maximum of 3 cycles (each cycle is 21 days). Following the completion of neoadjuvant therapy, all participants who are reassessed by MDT to be resectable after neoadjuvant treatment and have adequate lung functions would be provided with definite surgery. Otherwise, patients would be provided with radical radiotherapy through MDT discussion. For the surgery cohort, participants meet both the R0 resection, the pathological assessment criteria of pCR and have two consecutive landmark ctDNA tests that are negative will receive surveillance after surgery. Participants who do not meet all the above conditions will receive alectinib after surgery, adjuvant treatment should be initiated ideally 4-12 weeks after surgery, or according to local standard of care, treatment will continue until completion of treatment period (24 months), disease recurrence, unacceptable toxicity, death, or withdrawal from the study, whichever occurs first. For the radical radiotherapy cohort, participants will receive alectinib after radiotherapy, adjuvant treatment should be initiated ideally 4-12 weeks after surgery, or according to local standard of care, the treatment will continue until completion of treatment period (24 months), disease progression, unacceptable toxicity, death, or withdrawal from the study, whichever occurs first.

The purpose of this research is to see if monitoring the brain using magnetic resonance imaging (MRI) after radiation therapy will allow investigators to find cancer that has spread to the brain (brain metastases) before it causes symptoms.

This research study aims to determine what effects (good and bad) Durvalumab has on participants and their cancer with a "quick start" of Durvalumab within 14 days of finishing chemotherapy and radiation. The study will also determine the logistic barriers to the quick start of Durvalumab.