Inclusion Criteria:

• diagnosis of non-small cell lung cancer
• measurable or evaluable disease
• primary tumor must be documented by histopathic analysis
• disease recurrences occurring greater than five years after original diagnosis must be biopsy proven
• treatment with only one prior chemotherapy regimen for advanced disease (one additional prior regimen was allowed for neoadjuvant, adjuvant, or neoadjuvant plus adjuvant therapy)
• serum creatinine < 2mg/dl, or a calculated creatinine clearance > 40cc/min using the following formula: (140-age) x WT(kg) x 0.85 (if female 0.72) x creatinine (mg/dl). Tests must be done within 28 days prior to registration
• must have a CT scan (chest & abdomen) within 4 weeks prior to registration
• Zubrod performance status of 0-3

Exclusion Criteria:

• women who are pregnant or nursing
• no other prior malignancy is allowed except for: adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, adequately treated Stage I or II cancer from which the patient is currently in complete remission, or any other cancer from which the patient has been disease-free for 5 years
• history of ventricular fibrillation, sinus node or AV nodal disease, Wolff Parkinson White Syndrome, evidence of congestive heart failure, chest pain with exertion, hemodynamically significant or life threatening cardiac arrhythmia, or evidence of prior myocardial infarction on EKG. EKG must have been done within 28 days prior to registration. A normal cardiac stress test within 182 days prior to registration is required for all patients over 50 years old or those with abnormal EKG or any history of cardiac disease.
• hypersensitivity to erlotinib and/or Digoxin
• abnormal levels of K, Mg, and/or Ca, or conditions which cause such abnormalities (e.g. malnutrition, severe diarrhea, prolonged vomiting, dialysis, GI suction, untreated hypothyroidism, and use of diuretics, amphotericin B, steroids, or antacids)