DISEASE CHARACTERISTICS:

• Cytologically or histologically confirmed diagnosis of 1 of the following:

  • Metastatic breast cancer
  • Colorectal cancer
  • Gastric cancer
  • Lung cancer
  • Ovarian cancer
  • Pancreatic cancer
  • Hormone-refractory prostate cancer

• Scheduled to undergo chemotherapy for ≥ 3 months

  • Chemotherapy for colorectal, gastric, lung, ovarian, or pancreatic cancer may be administered in the neoadjuvant, adjuvant, or palliative setting

• History of deep vein thrombosis or pulmonary embolism allowed if treatment and secondary prevention of the last episode was completed prior to study entry

  • Negative baseline bilateral compression ultrasonography

PATIENT CHARACTERISTICS:

• Life expectancy > 3 months

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics

• More than 6 weeks since prior chemotherapy*

  • Hormonal therapy alone is not considered chemotherapy

• More than 4 weeks since prior major surgery, including surgery for cancer

  • Minor surgery (e.g., implant of a port-a-cath) within the past 4 weeks allowed
• No concurrent major surgery, including surgery for cancer, during the observation period
• Radiotherapy before or during the observation period allowed
• Concurrent chemotherapy* in combination with additional hormonal therapy allowed
• Concurrent treatment (with the exception of antithrombotic therapy) in any other clinical trial allowed

• No concurrent or scheduled use of thromboprophylaxis or any anticoagulant therapy, including any of the following:

  • Parenteral anticoagulants (e.g., heparin, low molecular-weight heparin, or other agents, such as fondaparinux or bivalirudin)
  • Oral anticoagulants (e.g., vitamin K antagonists)

  • Thrombolytic agents

    • Chronic treatment with antiplatelet agents, such as low-dose aspirin (≤ 300 mg/day) or clopidogrel allowed NOTE: *Chemotherapy is defined as treatment with any antineoplastic agent, including biologicals