USING heat to help deliver drugs to the heart of tumours could become the latest weapon in the fight against cancer.
The approach combines heat with an existing cancer therapy in which drugs are encased in fatty globules called liposomes. In trials in women with breast cancer, the results have exceeded expectations. And the next generation of such treatments promises to be even more effective.
Delivering chemotherapy drugs in liposomes is one way to minimise the damage chemotherapy does to healthy organs. Because the blood vessels in tumours tend to be leaky, liposomes can enter cancers but don鈥檛 affect tissues such as hair follicles, for instance, so you don鈥檛 lose your hair.
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Liposomes are already approved for chemotherapy but various groups are trying to make them more effective. A team at the Duke Comprehensive Cancer Center in North Carolina is heating up tumours with microwaves as the liposomes are given to patients. This opens up the pores in blood vessels, letting even more liposomes into the tumours.
The results from an initial trial on 21 women who had just been diagnosed with very severe and in most cases inoperable breast cancer were announced last week. In all 21 the tumours stopped growing, and most either shrank or were completely destroyed. The women nicknamed the therapy the 鈥渂ooby Jacuzzi鈥�, because they had to lie with their breasts immersed in hot water.
A similar trial of patients with recurrent breast cancer has taken place at the University of California, San Francisco, also with encouraging results, says researcher John Park. And the company Celsion, of Columbia, Maryland, plans to test the technique on prostate cancer.
The Duke results are very encouraging, says Francis Szoka of the University of California, San Francisco, one of the pioneers of liposome technology, because it鈥檚 far from easy to heat tumour tissues evenly. Blackwell herself is even more optimistic about the next generation of treatments. The liposomes used nowadays melt at around 43 掳C, a temperature that鈥檚 hard to reach inside tissues. But Mark Dewhirst and David Needham of Duke University have developed ones that melt between 39.5 and 40 掳C. 鈥淭hat鈥檚 the kind of temperature that you can achieve easily,鈥� says Dewhirst. These liposomes will also release their contents in just 20 seconds, compared with the hours it takes for some formulations.
Other researchers are investigating different ways of targeting tumours with liposomes. Szoka, for instance, is tacking sugar molecules that stick only to the surface of tumour cells onto the globules. Another approach is to attach antibodies that bind to cancer cells.