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Sometimes a great new word evokes curiosity, so I have used it to title this post and see if a few of you thought it would be worth looking at rather than sending to your “junk” email. You can’t find it in the dictionary, interestingly enough, but it’s related in derivation to Theranos, the bizarre company started by Elizabeth Holmes and if you haven’t read “Bad Blood” or seen the video you can find that story here:
For us prostate cancer followers, however, theranostics represent a “new” field in which the same/similar drugs can potentially be used for both diagnosis and therapy. There is a nice review of an ASCO educational presentation on the topic here. The main idea is that a radioisotope can be specifically directed to a target for either diagnosis or therapy. One of the oldest examples of this is radioiodine which is taken up by the thyroid gland. If you have thyroid cancer, the metastases will also take up the radioactive iodine and with nuclear medicine detectors you can see them, or if you inject even more, it will be “hot” enough to kill them.
223Ra is an isotope that seeks bone, just like calcium, and where there is more bone turnover/remodeling, more of it accumulates. As a drug, it was given the name Xofigo, and was approved for treating prostate cancer in men with bone dominant disease in 2013. It emits alpha particles, which are known as “high Linear Energy Transfer” radiation because they go only a very short distance before interacting with cancer cells and killing them. This is important since you would not want the radiation to kill the normal bone marrow cells that live in the same neighborhood. In the study leading to approval of 223Ra, men with symptomatic bone metastases and no visceral (e.g. liver or lung) metastases who received the isotope as a monthly injection for 6 months lived 14.9 months as compared to 11.3 months for placebo (P<0.001) and had fewer skeletal events and less bone pain. I always loved alpha emitters because I had the fun of making a cloud chamber for a science fair when I was in 6th grade. You might want to help a grandchild do that!
177Lutetium (177Lu) is an isotope that allows both diagnosis and therapy because it emits gamma radiation for detection, and high energy beta radiation that can kill cancer cells. When bound to PSMA (see these posts)
177Lu becomes a theranostic that shows considerable promise for treating prostate cancer. There are a number of completed trials of 177Lu-PSMA that have been summarized in this table:
For more details on 177Lu-PSMA treatment, this is an excellent recent review from the European Society of Radiology:
There are a number of ongoing trials of 177Lu-PSMA that you can find here.
Keep wearing your masks to protect your fellow prostate cancer groupies, be patriotic, and if you want to pay homage to one of the great scientists whose research led to these advances, look no farther than Radioactive, the recent Amazon Prime movie about Marie Curie. As one of the commentators on the trailer posted, “In a world full of Kardashian’s… be Madam Curie.”