CANBESURE STUDY (Cancer, Bemiparin and Surgery Evaluation)

Inclusion Criteria:

* Patients of 40 years of age or older, of either sex, who have given their informed consent to participate in the study.
* Patients with a malignant neoplastic process (primary or metastasic) of the gastrointestinal tract (except the oesophagus), genitourinary tract or female reproductive organs, previously diagnosed and documented, and who are programmed to undergo elective, open, curative or palliative surgery directly related to that disease.
* Patients undergoing surgery with general or spinal anaesthesia, with an estimated duration of surgery of over 30 minutes.
* Patients with a life expectancy of at least 3 months.

Exclusion Criteria:

* Curative or palliative surgery of a malignant neoplastic process in liver, biliary tract or pancreas.
* Women who are pregnant or breast-feeding, or women with child-bearing potential who are not using effective contraceptive methods.
* Patients with macrohaematuria, active haemorrhage within the past two months, organ lesions at risk of bleeding (e.g. active peptic ulcer, haemorrhagic cerebrovascular accident, aneurysms), a history of episodes of clinically evident haemorrhage, major surgery in the previous month or an increase in the risk of bleeding due to any disturbance of haemostasis which would contraindicate the anticoagulant therapy, with the exception of bleedings episodes directly caused by tumour subjected to the surgical intervention.
* Patients with known hypersensitivity to the LMWHs, to heparin or to substances of porcine origin.
* Patients with known hypersensitivity to radiological contrast media.
* Patients with known hypersensitivity to anaesthetic drugs or pre-anaesthetic drugs.
* Patients with a congenital or acquired bleeding diathesis (confirmed by hematological test), with or without haematuria.
* Lesions or surgical interventions of the central nervous system, eyes or ears within the previous 6 months, including hemorrhagic or ischemic cerebro-vascular accident, cerebral thrombosis and/or known cerebral metastasis.
* Disseminated Intravascular Coagulation (DIC) attributable to heparin-induced thrombocytopenia.
* Acute bacterial endocarditis and slow endocarditis.
* Patients on treatment with oral or parenteral anticoagulants within 5 days before the operation.
* Patients with a history of thrombocytopenia associated with heparin or with a current platelet count \<75,000/mm3.
* Patients with renal failure (defined as a serum creatinine over 2 mg/dL), hepatic insufficiency (with AST and/or ALT values \> 5 times over normal values established by the reference range of the local laboratory of the hospital).
* Severe arterial hypertension (systolic blood pressure over 200 mmHg and/or diastolic blood pressure over 120 mmHg).
* One or more documented episodes of DVT and/or PE (confirmed by a ventilation-perfusion gamma scan or helical CT) in the previous 3 months.
* Patients with suspected or confirmed inability to comply with the study treatment and/or follow-up.
* Patients who are participating in another clinical trial or who have done so in the past 30 days.
* Patients with a cava vein filter in place.
* Patients needing the use of unallowed concomitant treatments or medications such as more than 125mg/day aspirin, NSAIDs with long half-life of significant anti-aggregation activity, metformin, or any anticoagulant compound (please refer to section of the protocol "Concomitant medications and treatments" for details)