This study will test if local therapies in addition to erlotinib can improve responses and delay the time until new treatment is required. This study will also collect blood samples for research blood tests.

Inclusion Criteria:

• Newly diagnosed metastatic lung adenocarcinoma (recurrent or de novo) harboring sensitizing EGFR mutations (L858R, exon 19 deletion, G719A, L861Q, S768I, exon 19 insertions) with oligometastatic disease (≤5 discrete lesions of disease irrespective of location, inclusive of the primary lesion):
• all sites of disease must be amenable to definitive treatment with a local therapy (surgical resection, stereotactic radiosurgery, ablation and conventional radiation therapy) as determined by surgery, interventional radiology and radiation oncology
• all intrathoracic lymph nodes (including hilar, mediastinal, and supraclavicular nodal disease) are considered 1 discrete lesion.
• Each brain metastasis is included as a distinct lesion.
• Patients already started on erlotinib are eligible as long as their sites of disease are determined to be eligible for definitive local therapy by consensus of the principal investigators within 12 weeks of the patient first taking erlotinib.
• Lung adenocarcinoma histology confirmed at MSKCC.
• Available archived tissue to perform molecular analysis
• Patients without available archived tissue can have repeat biopsies to determine EGFR status as per standard clinical care guidelines
• Age 18 years or older
• Karnofsky Performance Status ≥ 70%
• Adequate bone marrow, liver and renal function, as specified below:
• Absolute Neutrophil Count (ANC) ≥ 1.5 x 109/L
• Hemoglobin ≥ 8 g/dL
• Platelets ≥ 100 x 109/L
• Serum total bilirubin ≤ 1.5 x upper limit of normal (ULN) (except for patients with documented Gilbert's Syndrome)
• AST and ALT ≤ 2.5 x ULN or ≤ 5 x ULN if liver metastases are present
• Serum creatinine ≤ 1.5 x upper limit of normal or creatinine clearance ≥ 60ml/min for patients with creatinine levels above institutional normal.
• For women of child-bearing potential, negative pregnancy test within 14 days prior to starting treatment
• Men and women of childbearing age must be willing to use effective contraception while on treatment and for at least 3 months thereafter

Exclusion Criteria:

• Treatment with erlotinib prior to developing metastatic disease
• Patients with activating but not sensitizing mutations (exon 20 insertions, EGFR T790M)
• Malignant pleural effusion or pleural disease
• Leptomeningeal disease
• Any site of disease that is not amenable to definitively local therapy including surgery or radiation therapy
• Women who are breastfeeding or pregnant
• Concurrent malignancies other than non-melanoma skin cancer that require active ongoing treatment.
• Any medical co-morbidities that would preclude surgery or radiation therapy