• Body weight \>/= 30 kg at screening

• Willingness and ability to use the electronic device(s) or application(s) for the electronic patient-reported outcome (PRO)

• Whole-body positron emission tomography/computed tomography scan (PET/CT) (from the base of skull to mid-thighs) for the purposes of staging, performed prior and within 42 days for Cohort A2 (ROS1 positive) and 50 days for Cohort A1 (ALK positive) of the first dose of cCRT or sCRT

• Histologically or cytologically documented locally advanced, unresectable Stage III NSCLC of either squamous or non-squamous histology

• Prior receipt of at least two prior cycles of platinum-based chemotherapy given concurrently with radiotherapy (cCRT); or at least two prior cycles of platinum-based chemotherapy given prior to radiotherapy (sCRT)

• The RT component in the cCRT or sCRT must have been at a total dose of radiation of 60 (+/-10%) Gy (54 Gy to 66 Gy) administered by intensity-modulated radiotherapy (preferred) or three dimension (3D)-conforming technique

• No disease progression during or following platinum-based cCRT or sCRT

• Life expectancy \>/= 12 weeks

• Confirmed availability of a representative formalin-fixed, paraffin-embedded (FFPE) tumor specimen

• Tumor PD-L1 status (TC score \< 1% vs. \>/= 1% vs. unknown) as determined using the VENTANA PD-L1 IHC SP263 assay (preferred) or the Dako PD-L1 IHC 22C3 pharmDx assay

• Eastern Cooperative Oncology Group Performance Status of 0, 1, or 2

• Adequate hematologic and end-organ function

• For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraception, and agreement to refrain from donating eggs, as defined by the protocol

• For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods, and agreement to refrain from donating sperm, as defined by the protocol

• Documented ALK fusion positivity by an eligible result from: centralized multiplex molecular testing of tumor tissue at the Sponsor's designated central laboratory under Study BX43361 or prior tissue-based testing performed in an accredited or certified laboratory

• Documented ROS1 fusion positivity by an eligible result from: centralized multiplex molecular testing of tumor tissue at the Sponsor's designated central laboratory under Study BX43361 or available results from a Sponsor pre-approved local, appropriately validated ROS1 fusion test on tumor tissue performed in a Clinical Laboratory Improvement Amendments certified or equivalent laboratory

• Ability to swallow entrectinib intact, without chewing, crushing, or opening the capsules