Metronomic therapy with cyclophosphamide induces rat lymphoma and sarcoma regression, and is devoid of toxicity

Background: Our aim was to investigate the clinical efficacy and toxicity of metronomic administration of low-dose cyclophosphamide (Cy) in lymphoma and sarcoma rat tumour models. Methods: Adult inbred rats were challenged with lymphoma TACB and sarcoma 13100 s.c. on day 0. Animals were divided into two groups: group 1, control, injected with saline three times a week; and group II, treated with Cy 10 mg/kg three times a week, from day 10 until the tumour was nonpalpable, or 5 mg/kg three times a week from day 7. Tumours were measured and animals were weighed twice weekly. Periodic blood samples were taken for determination of urea, creatinine, serum glutamic-oxaloacetic transaminase, lactate dehydrogenase and haematological parameters. Results: The administration of low-dose Cy eradicated established rat lymphomas and sarcomas; there was neither metastatic growth nor recurrence at primary sites for 100% of the lymphomas and 83% of the sarcomas. In addition, the treatment did not cause weight loss, and was devoid of haematological, cardiac, hepatic and renal toxicity. Conclusions: Metronomic administration of Cy at low doses on a thrice weekly schedule to already grown rat lymphomas and sarcomas demonstrated itself to be a successful antitumour therapy that did not cause weight loss and was devoid of haematological, cardiac, hepatic and renal toxicity.