Brachytherapy clinical applications

Highly targeted radiotherapy ( brachytherapy ) was the first clinical application of stain-etched silicon microparticles. We briefly review here the manufacture, testing, and clinical use of the P Si beta-emitting formulation for unresectable hepatocellular and pancreatic carcinoma. Clinical data Ifom a number of trials suggests that the technology offers patients with inoperable solid tumors an attractive alternative to external beam radiotherapy. 

Brachytherapy Sources. The first 252cf sources for radiotherapy research were prepared at SRL about fourteen years ago (4 5). Initially, these sources resembled the classical radium needles familiar in clinical radiotherapy. Eventually, afterloading cells and applicator tubes were supplied to medical evaluators, and all medical sources were improved by the use of californium-palladium cermet wire sheathed in Pt - 10% Ir alloy (6, 7). The most recent designs for medical sources produced in quantity for therapy research are line sources and point sources containing a range of Cf from iess than 1 yg to 200 yg (Figures 9 and 10). 

Californium-252 attracted early attention as a possible therapeutic agent in cancer treatment. The general impression formed from early work was that neutron therapy was inferior to x-ray therapy. More recent studies, however, indicate that neutron irradiation may have advantages over x-rays or y-rays in certain situations. In the period 1976-82, several hundred cancer cases were treated by neutron irradiation supplied by Cf [94]. Although not a cure, Cf neutron therapy appears to have promise in the treatment of pelvic cancer and in brachytherapy (short exposure therapy). Neutrons appear to have particular utility in tumors whose oxygen supply is impaired, and which, as a consequence, are relatively insensitive to x-rays or y-rays. While the applications of neutrons in the treatment of cancer are still experimental, there is a possibility that further clinical studies may well find a use for the neutron-emitting californium isotopes in therapy. 

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