Radical radiotherapy is critical for locally advanced non small cell lung cancer(NSCLC ). Our previous sturdy indicated that patients who received induction immunotherapy and subsequent radiotherapy suffered higher proportion of pneumonitis.Grade 2 or more pneumonitis patients have worse prognosis. It is urged to optimize the radiotherapy dose and target volume for patients treated with immunotherapy and radiotherapy. According to retrospective and prospective studies, omitting CTV radiation is feasible for patients undergoing concurrent radio-chemotherapy for locally advanced NSCLC. It is postulated that omitting CTV radiation for patients responded to induction therapy with immunotherapy and chemotherapy will have less pneumonitis without sacrificing the local control rate. Omitting CTV may also retain better immune function which will facilitate the immunotherapy.

Inclusion Criteria:

1. Histologically or cytologically confirmed non-small cell lung cancer;
2. stage IIIA or IIIB or IIIC according to the 8th edition of the TNM cancer staging system of the American Joint Committee on Cancer (AJCC) and Union for International Cancer Control（UICC);
3. inoperable or refuses surgery after induction therapy with immunotherapy and chemoradiotherapy;
4. After ≥2 cycles of induction chemotherapy combined with immunotherapy, the efficacy was CR, PR or SD (with a decreasing trend);
5. performance status 0-1;
6. measurable or evaluable lesions;
7. Survival expectancy is not less than 6 months;
8. adequate cardiac, pulmonary, renal, and hepatic and bone marrow function

Exclusion Criteria:

1. tumor progress after induction with immunothearoy and chemotherapy
2. EGFR, ALK, or ROS1 mutation;
3. Previous thoracic radiotherapy;
4. grade 2 or more immune-related adverse events after induction immunotherapy
5. Previous malignancies (except stage I non-melanic skin cancer or cervical carcinoma in situ);
6. Pregnant or lactating women
7. undergoing other clinical trials;
8. Have serious comorbidities, including myocardial infarction, severe arrhythmia, severe cerebrovascular disease, ulcer disease, psychosis and uncontrollable diabetes;
9. Patients with HIV positive and undergoing antiviral therapy;
10. Active tuberculosis