DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed metastatic colorectal cancer

• Received prior first-line chemotherapy with oral or intravenous fluoropyrimidine alone or in combination with irinotecan or oxaliplatin

  • Chemotherapy must have been given in combination with a standard dose of bevacizumab for 16-24 weeks as part of first-line treatment for metastatic colorectal cancer
• Stable disease, partial response, or complete response after completion of first-line treatment as documented by abdominal and thoracic CT scan, MRI, or x-ray within the past 21 days

• No clinical symptoms or history of CNS metastases

  • No imaging required in asymptomatic patients

PATIENT CHARACTERISTICS:

• WHO performance status 0-1
• Serum creatinine < 2.0 mg/dL or 177 μmol/L
• Proteinuria < 2+ by urine dipstick OR urine protein ≤ 1 g by 24-hour urine collection
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 12 months after completion of study therapy
• Must have basic health insurance with a Swiss health insurance company
• Patients must be compliant and in geographic proximity to allow proper staging and follow-up

• No medical reason that prohibits further bevacizumab treatment, including any of the following:

  • Uncontrolled hypertension (systolic blood pressure [BP] > 150 mm Hg and/or diastolic BP > 100 mm Hg) or clinically significant (i.e., active) cardiovascular disease
  • Serious non-healing wound, active peptic ulcer, or non-healing bone fracture
  • History of abdominal fistula, gastrointestinal perforation, or intra-abdominal abscess within the past 6 months
  • History or evidence of inherited bleeding diathesis or coagulopathy with the risk of bleeding
• No serious underlying medical condition that, in the judgment of the investigator, could further impair the ability of the patient to participate in the trial (e.g., active autoimmune disease or uncontrolled diabetes)
• No psychiatric disorder that would preclude patient understanding of study-related topics or giving informed consent

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 4 weeks since prior bevacizumab
• No prior anti-EGFR treatment (e.g., cetuximab) during first-line therapy
• No anticipation of concurrent major surgery (e.g., resection) or ablation of metastases
• No concurrent elective major surgery

• No concurrent daily aspirin exceeding 325 mg/day or clopidogrel exceeding 75 mg/day

  • Lower doses of the drugs noted above, or non-steroidal anti-inflammatory drugs with activity on platelets and gastric mucosa, or dipyridamole are allowed if given at a stable dose for ≥ 2 weeks prior to study entry
• No other concurrent experimental drugs or anticancer therapy