Inclusion Criteria:
1. Between the ages of 18 and 80.
2. ECOG general status score of 0-2 .
3. Primary non-small cell lung cancer (NSCLC) confirmed by histology or cytological pathology, T1-2N0M0, stage Ia-IIa (AJCC/UICC 8th edition).
4. The location of the tumor belongs to the peripheral type defined in this study (2cm and beyond (≥2cm) from the esophagus, main bronchial tree, spinal cord, heart, great blood vessels, brachial plexus and stomach, and 1cm and beyond (≥1cm) from the chest wall).
5. Medically inoperable, or patient refuses surgery.
6. Adequate organ function: 1). Blood function: absolute neutrophil count (ANC) ≥1.5 x 109/L, platelet count ≥80 x 109/L, hemoglobin ≥9 g/dL 2). Lung function: FEV1\>25%, DLCO\>25% 3). Cardiac function: no serious pulmonary hypertension, cardiovascular and cerebrovascular diseases, peripheral vascular diseases, serious chronic heart disease and other complications that may affect radiotherapy.4). Adequate liver function: total bilirubin \<1.5 times the upper limit of normal value, and AST, ALT\<2 times the upper limit of normal value. 5). Adequate renal function: serum creatinine ≤1.5 times the upper limit of normal or calculated creatinine clearance ≥50 ml /min, and urinary protein \<2+. Patients with a baseline urinary protein level of 2+ or more should have a 24-hour urine collection and evidence of a 24-hour urinary protein level of 1g or less.
7. Sign the informed consent.
Exclusion Criteria:
1. Multiple primary tumors.
2. Patient fails to comply with the treatment protocol.
3. Complicated with other malignant tumors that have not been controlled.
4. Patient whose particle radiotherapy plan cannot meet the minimum target dose coverage and dose volume limitation requirements, or cannot meet the dose constrains of normal tissue or organs.
5. Chest radiation therapy or radioactive particle implantation history.
6. Cardiac pacemakers or other internal metal prosthesis implants that may be affected by high-energy radiation or may affect the dose distribution to the radiation target area.
7. Pregnancy (confirmed by serum or urine β-HCG test) or lactation period.
8. HIV positive. Hepatitis virus replication phase, need to receive antiviral therapy, but because of concomitant disease cannot receive antiviral therapy. Active stage of syphilis.
9. A history of mental illness may hinder the completion of treatment.
10. With serious comorbidity that may interfere with radiotherapy, including: (a) Acute infectious diseases or acute active phase of chronic infection. b) Unstable angina pectoris, congestive heart failure, myocardial infarction that has been hospitalized in the past 6 months. c) Exacerbations of chronic obstructive pulmonary disease or other respiratory conditions requiring hospitalization. d) Severely impaired immune function. e) Diseases with excessive sensitivity to radiation such as ataxia telangiectasia. f) Other diseases that may affect particle radiotherapy.
11. Other circumstances that the physician considers inappropriate to participate in clinical study.
