Incidence of Blood Clots in Patients Undergoing Chemotherapy for Solid Tumors

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