Sirtex warms to cancer therapy

Researchers with Sydney meditech company Sirtex Medical (ASX:SRX) have decided to continue development of a radical new therapy that would destroy liver cancers with focused heat, after its researchers reported encouraging progress in solving technical problems involved in scaling up the technique from animals to humans.

The Sirtex technology uses a powerful magnetic field to inductively heat dense aggregations of microspheres containing metallic particles, delivered to the tumour via the bloodstream.

At Sirtex's annual general meeting last October, Dr Steve Jones, head scientist on the hyperthermia project gave a progress report to shareholders, but CEO Bruce Gray then announced the project would not be funded beyond the end of the year unless it achieved key scientific milestones critical to its successful clinical application.

Sirtex said the milestones had been reached, and the company has decided to increase its commitment to the project. The company has also commissioned the University of Sydney to help in the final development phase of the technology.

Sirtex is already producing SirSpheres containing radioisotopes for cancer therapy, but the hyperthermia project employs a very different approach, according to Jones.

It exploits the unusual circulatory system of the liver to deliver the magnetically susceptible SirSpheres via the hepatic artery to the organ, where they aggregate in the highly vascularised tissue of the cancer.

A localised, high-frequency magnetic field is then applied to the cancer, heating the nanoparticles to 42 degrees Celsius, sufficient to induce apoptosis -- programmed cell death -- in the cancerous cells.

Jones said that while the technique worked successfully in an animal model, scaling it up for potential use in human cancer patients has been a technical challenge.

The requirement to generate a powerful magnetic field that could be used safely in humans placed severe constrains on the formulation of the microspheres, and the company has had to seek engineering help to construct a prototype device capable of being used in a clinical setting to generate generating a focused magnetic field.