DISEASE CHARACTERISTICS:

• Histologically confirmed non-small cell cancer

  • Recurrent disease after adjuvant treatment OR progressive disease after 1 prior treatment for recurrent or metastatic disease

• Received at least 1 prior chemotherapy regimen and meets the following criteria:

  • No more than 1 prior chemotherapeutic regimen in the recurrent or metastatic setting

  • Patients who received prior chemotherapy in the adjuvant setting are eligible when 1 of the following criteria is met:

    • In first recurrence (after 1 prior regimen)
    • Received first-line chemotherapy in the recurrent setting after 2 prior regimens

• Measurable disease

  • Must have ≥ 1 measurable target lesion outside prior radiotherapy field OR radiologic confirmation of disease progression within a prior radiotherapy field

• No known or untreated brain metastases or carcinomatous meningitis

  • Clinically stable, treated brain metastases allowed provided it has been > 7 days since prior steroids

PATIENT CHARACTERISTICS:

• ECOG performance status 0-1
• Life expectancy ≥ 3 months
• Absolute neutrophil count ≥ 1,500/mm³
• Platelet count ≥ 100,000/mm³
• Bilirubin ≤ 1.5 times upper limit of normal (ULN)
• AST and ALT ≤ 2.5 times ULN
• Creatinine ≤ 1.5 times ULN OR creatinine clearance ≥ 60 mL/min
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 3 months after completion of study treatment
• Able to swallow oral medication
• No concurrent medical condition that would preclude study compliance
• No history of allergic reaction to compounds of similar chemical or biological composition to gemcitabine hydrochloride or imatinib mesylate

• No uncontrolled illness that would preclude study compliance, including any of the following:

  • Symptomatic congestive heart failure
  • Unstable angina pectoris
  • Cardiac arrhythmia requiring therapy
  • Myocardial infarction within the past 6 months
  • Active infection
• No New York Heart Association class III-IV congestive heart failure
• No chronic liver disease (i.e., chronic active hepatitis, cirrhosis)
• No HIV positivity
• No other primary malignancies within the past 5 years, except carcinoma in situ of the cervix or nonmelanoma skin cancer

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 3 weeks since prior chemotherapy (6 weeks for nitrosoureas)
• At least 3 weeks since prior anti-vascular endothelial growth factor therapy and recovered
• At least 3 weeks since prior radiotherapy and recovered
• More than 28 days since prior and no other concurrent investigational or commercial agents
• More than 2 weeks since prior major surgery
• No prior gemcitabine hydrochloride or imatinib mesylate for metastatic disease
• No prior tyrosine kinase inhibitor, except for gefitinib or erlotinib hydrochloride
• No concurrent therapeutic warfarin (prophylactic warfarin therapy ≤ 1 mg daily allowed)
• No other concurrent medications that would preclude study compliance
• No concurrent chronic systemic corticosteroids