Inclusion Criteria:

1. Pathologically proven, unresected, locoregionally advanced NSCLC without evidence of hematogenous metastases (stage II-IIIB disease according to the 6th edition of the AJCC Staging Manual) with exception as defined by inclusion #2).
2. Patients with solitary brain metastasis without sign of progression in the brain at the time of registration will be eligible for this trial if there is clinical indication for concurrent chemoradiation to the primary disease in the lung.
3. Suitability for concurrent chemoradiation therapy per treating radiation oncologists or treating medical oncologist's: A) Karnofsky performance score of >/= 70, or ECOG 0-1 B) Unintentional weight loss </= 10% during the 3 months before study entry.
4. Receipt of induction chemotherapy followed by referral for concurrent chemoradiation.
5. Measurable disease on chest x-ray, contrast-enhanced CT, or PET scan.
6. Locoregional recurrence after surgical resection, if suitable for definitive concurrent chemoradiation.
7. Forced expiratory volume in the first second (FEV1) >/= 1 liters.
8. Fluorodeoxyglucose (FDG) -PET scan within 3 months before registration. The pretreatment (diagnostic) PET/CT should be performed together with the 4-D CT simulation. If PET/CT is not available, PET image acquired separately may be fused with the 4D CT.
9. Standard pretreatment evaluations (as decided by treating radiation oncologists, medical oncologist, surgeons or pulmonologists), to include MRI or CT scan of the brain, contrast CT scan of the thorax and upper abdomen, pulmonary function tests, lung and cardiac single proton emission computed tomography (SPECT), liver function tests (LFT), blood chemistry, renal function tests, and complete blood count.
10. Age >/= 18 years but </= 85 years.
11. A signed specific informed consent form before study entry.

Exclusion Criteria:

1. Small cell histology.
2. Prior radiotherapy to regions that would result in overlap of radiation therapy fields.
3. Pregnancy (female patients of childbearing potential must practice appropriate contraception).
4. Enrollment in a clinical trial that specifically excludes IGAPT treatment.
5. Patients with implanted device(s) that prohibit patients from having proton treatment (cardiac pace maker, defibrillator, neurotransmitter, etc).
6. Previous or concomitant malignancy other than (a) curatively treated carcinoma in situ of cervix, (b) basal cell carcinoma of the skin, (c) curatively treated superficial transitional cell carcinoma of the urinary bladder, and (d) early stage tumor treated more than 3 years ago for cure.