The core hypothesis to be tested is that the use of consolidative SBRT followed by maintenance chemotherapy in patients with less than or equal to 6 metastatic sites (primary + 5) will improve progression free survival (PFS) compared to maintenance chemotherapy alone.

This protocol is a randomized phase II trial of maintenance chemotherapy versus consolidative Stereotactic Body Radiation Therapy (SBRT) plus maintenance chemotherapy for patients with Stage IV non-small cell lung cancer (NSCLC).

Prior to accrual on the trial, patients with Stage IV NSCLC will be treated with standard first-line chemotherapy. Patients who achieve a partial response or stable disease by imaging criteria with fewer than or equal to six sites of oligometastatic disease will be randomized to maintenance chemotherapy or consolidative SBRT to all sites of disease (followed by maintenance chemotherapy at the medical oncologist's discretion). Choices of first line and maintenance chemotherapy will be determined by the medical oncologist based on clinical appropriateness.

Inclusion Criteria:

1. Patients must have biopsy proven metastatic NSCLC (Stage IV).

2. Patients must have received first line chemotherapy, from 4-6 cycles, and achieved stable disease or a partial response.

3. Patients receiving first-line erlotinib, crizotinib for EGFR mutant-positive or EML4-ALK positive NSCLC will be excluded.

4. Age ≥ 18 years

5. Patients must have measurable disease at baseline.

6. Patients can have up to only 6 discrete active extracranial lesions (≤3 in the liver and ≤3 in the lung) identified by diagnostic CT or PET/CT scan or MRI within 8 weeks prior to the initiation of SBRT.

   1. For patients who have received prior radiotherapy to the primary site in the lung, residual PET activity is difficult to interpret and will not be considered a site of active disease if the CT appearance is stable or improved over an interval of at least three months
   2. Patients who previously received radiotherapy to the primary site will be ineligible if there is CT evidence of disease progression within the past 3 months.
   3. Patients with previously un-irradiated primary sites will be potentially eligible, but special considerations apply (section 4.3.2).
   4. Up to 2 contiguous vertebral metastases will be considered a single site of disease.

7. Patients must have a KPS >60

8. AST, ALT & Alkaline phosphates must be ≤ 2.5X the upper limit of normal. Total bilirubin must be within the limit of normal.

9. Patients should have adequate bone marrow function as defined by peripheral granulocyte count of ≥1500/mm³.

10. Patients should have adequate renal function (serum creatinine ≤1.5 times the ULN).

11. Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study participation, and for 90 days following completion of therapy. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately.

    11.1 A female of child-bearing potential is any woman (regardless of sexual orientation, having undergone a tubal ligation, or remaining celibate by choice) who meets the following criteria:

    • Has not undergone a hysterectomy or bilateral oophorectomy; or
    • Has not been naturally postmenopausal for at least 12 consecutive months (i.e., has had menses at any time in the preceding 12 consecutive months).

12. Patients who would be receiving SBRT for lung tumors who are known or suspected by the treating radiation oncologist to have compromised lung function must have a documented forced expiratory volume in 1 second (FEV1) ≥ 1L.

13. Patients must provide verbal and written informed consent to participate in the study.

Exclusion Criteria:

1. Patients who previously received radiotherapy to the primary site with CT evidence of disease progression at the primary site within 3 months following the initial radiotherapy.
2. Patients with untreated brain metastases Patients with serious, uncontrolled, concurrent infection(s).
3. Significant weight loss (>10%) in the prior 3 months.
4. Because the tolerance dose of SBRT to the gastrointestinal tract is not established, patients with metastatic disease invading the esophagus, stomach, intestines, or mesenteric lymph nodes will not be eligible.
5. Patients with cutaneous metastasis of NSCLC.
6. Patients with more than 6 discrete extra-cranial lesions.
7. Participation in any investigational drug study within 4 weeks preceding the start of study treatment.
8. Unwillingness to participate or inability to comply with the protocol for the duration of the study.
9. Patients who are pregnant. Patients with reproductive capability will need to use adequate contraception during the time of participation in the study.