The main objective of this study is to compare the efficacy and safety of aspirin, low molecule heparin and rivaroxaban for preventing catheter-related thrombosis in middle-to-high-risk ambulatory patients with cancer and implantable venous access ports.

Study Type: Interventional, randomized, parallel Assignment and no masking

Study Arms & Intervention: Drug 1: Aspirin, 100mg/day orally; Drug 2: rivaroxaban, 10mg/day orally; Drug 3: low molecule heparin, 4000IU(0.4ml)/day subcutaneous injection; Reference: mechanical prophylaxis.

Follow-up Period: 6 months. The trial visits occurred at time before each chemotherapy cycle. The following details should be included at each visit: Khorana score, height and weight, blood routine examination, coagulation function, stool-routine and occult blood test, renal and liver function, ultrasonography of both legs and neck.

Primary Outcome: The primary efficacy end point was the occurrence of thrombus in the vein at the puncture site or nearby. The primary was the occurrence of a major bleeding event as defined by the International Society on Thrombosis and Haemostasis (ISTH).

Secondary Outcome: The secondary efficacy end point was occurrence of occurrence of other thrombosis or embolism events like deep vein thrombosis or pulmonary embolism. The secondary safety endpoint was the occurrence of any clinically relevant non-major bleeding, minor bleeding and adverse events.

Population: patients with cancer and implantable venous access ports

Eligibility Criteria:

1. Age 18-75 years;
2. Patients with malignant tumors who received implantable drug delivery devices as intravenous access for systematic chemotherapy;
3. Eastern Cooperative Oncology Group (ECOG) class 0-1;
4. Expected to receive chemotherapy within 1 week of enrollment;
5. Expected survival of more than 6 months;
6. Ambulatory patients or outpatient chemotherapy patients whose intravenous chemotherapy less than 24 hours per hospital stay;
7. Khorana score 1-3 point.

Exclusion Criteria:

1. Patients with a history of allergies to low molecular weight heparin, rivaroxaban, aspirin or other non-steroidal anti-inflammatory drugs, especially those with asthma, neurovascular edema or shock;
2. Patients with bleeding risks: thrombocytopenia (platelet count < 50*109/L), clinically significant active bleeding, active gastric ulcer disease, severe arterial hypertension, history of previous stroke;
3. moderate to severe liver and kidney dysfunction;
4. pregnant or lactating women;
5. patients who are administered systemically with pyrrole-antimycotic agents (eg ketoconazole, itraconazole, voriconazole and posaconazole) or HIV protease inhibitors (eg ritonavir);
6. Patients taking methotrexate;
7. Patients with systemic use of non-steroidal anti-inflammatory drugs;
8. Patients who have had anticoagulant drugs for any other reason.

Inclusion Criteria:

1. age 18-75 years;
2. patients with malignant tumors who received implantable drug delivery devices as intravenous access for systematic chemotherapy;
3. Eastern Cooperative Oncology Group (ECOG) class 0-1;
4. expected to receive chemotherapy within 1 week of enrollment;
5. expected survival of more than 6 months;
6. ambulatory patients or outpatient chemotherapy patients whose intravenous chemotherapy less than 24 hours per hospital stay;
7. Khorana score 1-3 point.

Exclusion Criteria:

1. patients with a history of allergies to low molecular weight heparin, rivaroxaban, aspirin or other non-steroidal anti-inflammatory drugs, especially those with asthma, neurovascular edema or shock;
2. patients with bleeding risks: thrombocytopenia (platelet count < 50*109/L), clinically significant active bleeding, active gastric ulcer disease, severe arterial hypertension, history of previous stroke;
3. moderate to severe liver and kidney dysfunction;
4. pregnant or lactating women;
5. patients who are administered systemically with pyrrole-antimycotic agents (eg ketoconazole, itraconazole, voriconazole and posaconazole) or HIV protease inhibitors (eg ritonavir);
6. patients taking methotrexate;
7. patients with systemic use of non-steroidal anti-inflammatory drugs;
8. patients who have had anticoagulant drugs for any other reason.