Reply to the article “Metronomic therapy with cyclophosphamide induces rat lymphoma and sarcoma regression, and is devoid of toxicity” by V. R. Rozados et al. (Ann Oncol 2004; 15: 1543–1550): … and in humans?

The Concept of Hormesis in Cancer Therapy - Is Less More?

There has, in recent years, been a paradigm shift in our understanding of the role of the immune system in the development of cancers. Immune dysregulation, manifesting as chronic inflammation, not only facilitates the growth and spread of tumors but prevents the host from mounting effective immune defenses against it. Many attempts are being made to develop novel immunotherapeutic strategies, but there is growing evidence that a radical reevaluation of the mode of action of chemotherapeutic agents and ionizing radiation is required in the light of advances in immunology.

Based on the concept of hormesis – defined as the presence of different modes of action of therapeutic modalities at different doses – a ‘repositioning’ of chemotherapy and radiotherapy may be required in all aspects of cancer management. In the case of chemotherapy, this may involve a change from the maximum tolerated dose concept to low dose intermittent (‘metronomic’) therapy, whilst in radiation therapy, highly accurate stereotactic targeting enables ablative, antigen-releasing (immunogenic) doses of radiation to be delivered to the tumor with sparing of surrounding normal tissues. Coupled with emerging immunotherapeutic procedures, the future of cancer treatment may well lie in repositioned chemotherapy, radiotherapy, and more localized debulking surgery.

Megestrol acetate versus metronomic cyclophosphamide in patients having exhausted all effective therapies under standard care

Background:

To evaluate the antitumour activity and safety of metronomic cyclophosphamide vs megestrol acetate in progressive and advanced cancer patients having exhausted all effective therapies under standard care.

Methods:

Patients were randomly assigned to receive orally metronomic cyclophosphamide (50 mg b.i.d) or megestrol acetate (160 mg only daily) until intolerance or progression (RECIST 1.0). The primary efficacy end point was a 2-month progression-free rate (PFR_2m). According to Optimal Simon's design and the following assumptions, namely, P0=5%, P1=20%, α=β=10%, the treatment is considered as effective if atleast 5 out of 44 patients achieved PFR_2m.

Results:

Between September 2006 and January 2009, 88 patients were enrolled. Two patients experienced grade 3–4 toxicities in each arm (4%). One toxic death occurred in the megestrol acetate arm as a consequence of thrombosis. The metronomic cyclophosphamide arm reached the predefined level of efficacy with a PFR_2m rate of 9 out of 44 and a PFR_4m rate of 5 out of 44. The MA arm failed to achieve the level of efficacy with a PFR_2m of 4 out of 44 and a PFR_4m of 1 out of 44. The median overall survival was 195 and 144 days in the metronomic cyclophosphamide arm and megestrol acetate arm, respectively.

Conclusion:

Metronomic cyclophosphamide is well tolerated and provides stable disease in such vulnerable and poor-prognosis cancer patients. This regimen warrants further evaluations.

The emerging low-dose therapy for advanced cancers

Generally minute doses of drugs have been prescribed in biotherapies, homeopathy, immunization and vaccinations for centuries. Now the use of low doses of drugs is on the rise to combat serious diseases such as advanced cancers around the world. This new therapeutic approach to address solid tumors and other advanced diseases is a departure from the conventional use of maximum dose protocol. A small dose of the prescribed drug is frequently administered in a continuous fashion, at regular intervals, either as a standard treatment or as a maintenance therapy for a long time. However, this new treatment method lacks any standard for drug quantization, dose fractionation, repetition frequency and duration of a treatment course for an individual patient. This paper reviews literature about metronomic therapy and discusses hormesis: both phenomena occur in low dose ranges. Better mathematical models, computer simulations, process optimization and clinical trials are warranted to fully exploit the potential of low dose metronomic therapy to cure chronic and complicated diseases. New protocols to standardize metronomic dosimetry will answer the age old questions related to hormesis and homeopathy. It appears that this new low-dose metronomic therapy will have far reaching effects in curing chronic diseases throughout the world.