Re: what are some diseases treated with nuclear medicine?

Nuclear medicine is usually used in the diagnosis of diseases, not their 
treatment. But you are very right that some diseases are in fact treated 
by nuclear medicine. Before I get to them, I would like to talk a little 
about diagnostic nuclear medicine and about the treatment of diseases by 
use of radiation.

Diagnostic nuclear medicine works by administering radioactive materials 
to a patient and seeing where they are taken up. These materials are 
selected because they are concentrated in the area of interest. They also 
emit radiation so that they can be detected and create an image for 
evaluation. Common nuclear medicine diagnostic studies are bone scans, 
heart scans, thyroid uptake and scans and pulmonary scans.

These diagnostic studies use small amounts of radiation. Such small 
amounts produce no detectable harm to cells. But large amounts of 
radiation can cause harm; they can damage or kill cells. Soon after the 
discovery of x-rays it became known that high doses of x-rays (about 
100,000 times the amount used for diagnostic studies) could be used to 
kill cancer cells while sparing normal cells. This is possible because 1) 
cancer cells are more sensitive to radiation than healthy cells, and 2) 
the radiation beam could be aimed to hit the cancer while avoiding to some 
degree the surrounding structures.

The same line of reasoning applies in the field of nuclear medicine. If 
small doses of radiation could be used for diagnosis, could larger doses 
be used for treatment? In some cases, the answer is “yes”. Here are some 
diseases that are treated by nuclear medicine:

Thyrotoxicosis (Grave’s Disease) – In this condition the thyroid is 
overactive and produces too much thyroid hormone. Radioactive Iodine-131 
is given orally and is taken up very strongly by the thyroid. The amount 
of I-131 given is calculated to be enough to damage thyroid function and 
so reduce the production of thyroid hormone. 

Thyroid Cancer – A large dose of I-131 is given. The principle is the same 
as in the treatment of thyrotoxicosis, but the dose is large enough to 
kill the thyroid cells and the cancer cells. This also can kill distant 
metastases.

Bone Cancer – Many cancers can spread to the bone. These bony metastases 
can produce severe and intractable pain. The radioactive materials 
Strontium-90 and Samarium-153-EDTMP go to the metastatic sites in the 
bone. They do not kill the cancer; rather, they decrease the sensitivity 
of the bone to pain. Thus, they are palliative treatments rather than 
curative treatments.

Polycythemia Vera – In this disease there is an increased number of red 
blood cells and an enlarged spleen. The radioactive element Phosphorus-32 
is taken up by the bone marrow. When given in the correct dose it reduces 
but does not destroy the production of red cells.

Malignant Pleural or Peritoneal Effusions – Some cancers produce fluid in 
the chest (pleural effusions) and in the abdomen (peritoneal effusions.) 
One way of treating these is to inject a Phosphorus-32 compound. The 
radiation decreases the production of fluid. This is a palliative 
treatment.

Rheumatiod Arthritis and other joint diseases – Some joint diseases 
produce thickened joint lining (synovium) which can produce a joint 
effusion and destroy bone and cartilage. Sometime the synovium can be 
surgically removed. Sometimes, in a procedure called “radionuclide 
synovectomy”, a radioactive agent is injected into the joint and used to 
destroy the overgrown joint lining. Many different elements can be used 
for this.

Liver Cancer –The injection of I-131 containing Lipiodol (an oil-based 
liquid) through a catheter into the hepatic artery can be used as a 
palliative treatment for hepatocellular carcinoma.

Work is being done on using monoclonal antibodies tagged with radioactive 
elements. Attempts are sometimes made to use nuclear medicine to treat 
certain brain tumors and adrenal tumors. And more advances will surely be 
coming.