DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed diagnosis of 1 of the following:

  • Gastrointestinal cancer*
  • Head and neck cancer*
  • Non-small cell lung cancer*

  • Colorectal adenocarcinoma** meeting the following criteria:

    • Unresectable disease
    • Evidence of new or progressive metastatic lesions within the past 6 months
    • At least 1 metastatic tumor site must be accessible for biopsy

• KRAS wild type by PCR assay or directed sequencing of KRAS exon and codons 12 and 13

  • May undergo a needle or excisional biopsy of a malignant site prior to enrollment if KRAS mutational status cannot be determined on archived tumor tissue
• Incurable, advanced disease

• Received ≥ 1 prior systemic regimen for advanced/metastatic disease, including fluorouracil and leucovorin calcium and either oxaliplatin or irinotecan hydrochloride**

  • Any type of prior antineoplastic therapy allowed, except for epidermal growth factor receptor (EGFR) inhibitors

• Measurable disease**, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques OR ≥ 10 mm by spiral CT scan

  • Target lesions may not be in a previously irradiated field unless progression of the lesion has been documented

• History of brain metastases allowed provided ≥ 1 of the following criteria are met:

  • Metastases have been surgically resected
  • Radiographically and clinically stable for 2 months after completion of radiotherapy NOTE: *Phase I only

NOTE: **Phase II only

PATIENT CHARACTERISTICS:

• ECOG performance status (PS) 0-2 OR Karnofsky PS 60-100%
• WBC ≥ 3,000/mm³
• Absolute neutrophil count ≥ 1,500/mm³
• Platelet count ≥ 100,000/mm³
• Bilirubin normal
• AST and ALT ≤ 2.5 times upper limit of normal
• Creatinine normal OR creatinine clearance ≥ 60 mL/min
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for ≥ 60 days after completion of study treatment
• Other prior malignancies allowed provided prior therapy has been discontinued and there is no evidence of disease
• Able to take and retain oral medications
• No history of allergic reactions attributed to compounds of similar chemical or biological composition to erlotinib hydrochloride or cetuximab
• No significant traumatic injury within the past 21 days
• No abnormalities of the cornea based on history (e.g., dry eye syndrome or Sjögren's syndrome), congenital abnormality (e.g., Fuch's dystrophy), abnormal slit-lamp examination using a vital dye (e.g., fluorescein or Bengal-Rose), and/or an abnormal corneal sensitivity test (Schirmer test or similar tear production test)
• No gastrointestinal tract disease resulting in an inability to take oral medication
• No requirement for IV alimentation
• No active peptic ulcer disease

• No uncontrolled intercurrent illness, including, but not limited to, any of the following:

  • Ongoing or active infection
  • Symptomatic congestive heart failure
  • Unstable angina pectoris
  • Cardiac arrhythmia
  • Psychiatric illness or social situation that would preclude study compliance

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 4 weeks since prior biologic therapy, chemotherapy, or radiotherapy (6 weeks for nitrosoureas or mitomycin C) and recovered
• No prior EGFR-targeting therapies
• No prior surgical procedures affecting absorption
• At least 21 days since prior major surgery or biopsy of a parenchymal organ
• No concurrent CYP3A4-inducing agents
• No other concurrent investigational agents
• No other concurrent anticancer agents or therapies
• No concurrent combination antiretroviral therapy for HIV-positive patients