266 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1951 



the gamma rays emitted by it, research workers have found that 

 iodine is concentrated by the thyroid gland. They have also found 

 how much iodine is absorbed and excreted and at what rate. 



Kadioisotopes can also produce cancer. This is turned to account 

 in cancer research by using some of them, strontium 89, for example, 

 to induce cancer in experimental animals for studies that may throw 

 light upon cancer in human beings. 



In addition to their usefulness in research directed toward increas- 

 ing our knowledge of cancer and the tissues it destroys, radioisotopes 

 are being employed in diagnosis, to detect and locate cancer. It has 

 been difficult, in the past, to estimate the exact location of a brain 

 tumor by means of external signs on the patient's body or by X-ray 

 studies. Now, by injecting radioactive phosphorus in tracer amounts 

 and relying on the tumor in its rapid growth to take up more of it 

 than the slow-growing normal tissues surrounding it do, a physician, 

 using a counter, can compare the radioactivity in different parts of 

 the brain and locate the tumor more precisely than before. 



'The final use of radioisotopes is in therapy, to inhibit or destroy 

 cancer. A somewhat complex case at the Montefiore Hospital, New 

 York, involving the use of radioactive iodine, will illustrate both 

 diagnosis and therapy. In 1923 the patient had his cancerous thyroid 

 gland removed by surgery. For the 16 years following he was well. 

 Then he reported to Montefiore with a tumor in his back which, after 

 surgical removal, turned out to be a metastatic cancer of the thyroid. 

 The cancerous thyroid gland that had been removed 16 years before 

 had spread before its removal and was now showing up in another 

 locality. In the next 4 years it showed up in still other places, metas- 

 tases that X-ray therapy could not control. By means of tracer doses 

 of radioiodine, the metastases in skull, lung, ribs, spine, pelvis, and 

 femur were revealed to be getting worse. Therapeutic doses of radio- 

 iodine were then resorted to. The patient got better and is still well 

 today, 5 years after the first radioactive therapy. The radioiodine 

 saved, or at least prolonged, the patient's life; it is only fair to add 

 that most cases are not so fortunate. 



In this case, as in all the previous ones mentioned, radioisotopes 

 were used because of their characteristic behavior as tracers. But in 

 the therapy of tliis case, two other characteristics come into play. 

 One is that radiation has uneven effects upon various kinds of tissue, 

 and cancerous tissue is generally more susceptible to radiation than 

 normal tissue. The other is a characteristic which radioisotopes share 

 with stable isotopes; certain ones have, as elements, an aflfinity for 

 certain tissues — phosphorus for bone and iodine for thyroid are ex- 

 amples. These traits have led to the hope of finding a substance that 

 will have such an affinity for cancerous tissue that enough of it, radio- 

 actively impregnated, can be deposited in the cancer to kill it. So 



