Introduction to alpha emitters
There is a potential breakthrough in the treatment of cancer: alpha emitting radionuclides. A Toronto conference on alpha emitters for medical therapy in June 1998 (whose proceedings have been published by the U.S. Department of Energy) concluded that (1):
… the particular promise lies in applying appropriate carriers of alpha emitters to reach the target cells within a given time frame that allows for maximal local treatment with minimal exposure of normal cells.
This scenario is in disseminated disease with single cell distributions such as in various hematological malignancies, or in the case of micrometastases. The early treatment of micrometastasis may save lives.
For instance, micrometastatic spread of cancer already is present in about 30% of colorectal cancer when first diagnosed; an early successful eradication is feasible and treatment should be vigorous. The future clinical potential for alpha emitter therapy in such situations is huge.
Another large promise holds the effective treatment of bone pain by local irradiation with alpha particles. Radiation-synovectomy is being considered for alpha emitter application that can be precisely localized in the cells of the inflamed synovial membrane following intra-articular injection of the appropriately chosen carrier of the emitter. This particularly holds for treating rheumatoid arthritis.
Moreover, certain cells in the immune system were discussed as targets for alpha emitters; thus, targets may be lymphoid cells carrying the human-immune-deficiency (HIV) virus, or immune competent cells to avoid the graft versus host reaction after cell or organ transplantation.
Other candidate targets were mentioned, for instance, bacteria resistant to antibiotics but accessible to chemicals that may serve as carriers of the alpha emitter.
Alpha emitters are already being employed as radiation sources for stents placed into the coronary arteries in order to prevent vessel occlusion by arresting proliferation of the endothelial cells lining the arteries.
The challenging difficulty in all these potential applications is the localized placement of the alpha emitter on or into the chosen target with minimal effects to normal cells and tissues.
In other words, alpha emitters can treat hematological malignancies and micro metastases with minimal damage to normal cells. They may have widespread application in the treatment of colorectal cancer (90,000 new cases a year in the U.S. alone). They can relieve bone pain and treat rheumatoid arthritis. As well, there are potential treatments of HIV, transplant rejection and patients whose bacterial illness is resistant to antibiotics. Alpha emitters are already being used to produce radioactive stents placed in the coronary artery to keep the circulatory system healthy.
- (1) Alpha Emitters for Medical Therapy : Second Bi-annual Workshop, Toronto, Canada, 1998 June 4-5; compiled and edited by Feinendegen, Ludwig E. and McClure, John J.; published by U.S. Department of Energy