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This week brought excellent and exciting news from the ASCO GU Meeting about management of high risk prostate cancer using “triple therapy” for metastatic disease. Adding further evidence for the “kitchen sink” approach, Matt Smith from MGH presented data from the ARASENS trial. The study involved 1306 patients with metastatic prostate cancer (86% of whom presented with metastases and the remainder of whom developed mets while being followed after primary treatment). The trial evaluated whether adding the potent anti-androgen, darolutamide aka Nubeqa® (similar to enzalutamide and apalutamide) to standard ADT (e.g. orchiectomy, leuprolide, or other GnRH analog) plus docetaxel (Taxotere®) could improve survival. We already knew that 6 cycles of docetaxel added to ADT in this situation improved survival from the CHAARTED trial I wrote a blog about several years ago. This was the trial design:
The results of the trial were very positive and represent a new “standard of care” for patients with metastatic prostate cancer:
Although it is too early to say whether some of the patients in this or similar trials, such as PEACE 1, have been cured, it is clear that throwing the “kitchen sink” at prostate cancer can offer real improvement in survival. Now the questions become: Who are the patients most likely to benefit? What kind of toxicities do these patients have to put up with? How much does this kind of treatment cost? What if we added other known effective treatments like Lu-177-PSMA or PARP inhibitors to appropriately selected patients? Would adding this kind of treatment cure some patients with oligometastatic disease? And perhaps most intriguing, could we imagine applying this kind of treatment to patients with newly diagnosed, localized (but high risk …e.g. Gleason 8,9,10, or node positive) disease as part of a plan that involved prostate surgery or radiation?
The answer to all of these questions will come only from appropriately designed clinical trials. I am reminded, too, of the famous quote from one of the pioneers in prostate cancer treatment, Dr. Willit Whitmore who said, “Is cure possible? Is cure necessary? Is cure possible only when it is not necessary?” There are obvious differences between the 52 year old man who presents with high risk prostate cancer and is otherwise healthy versus a 79 year old gentleman who had prostate surgery 15 years ago, a pacemaker, and now has a rising PSA with only one or two metastases showing up on a PSMA-PET scan.
The progress in prostate cancer research has accelerated dramatically during my career. As well, the costs of oncologic care are rising at a faster rate than can be maintained, “National costs for cancer care were estimated to be $190.2 billion in 2015 and $208.9 billion in 2020 (2020 U.S. dollars), an increase of 10 percent that is only due to the aging and growth of the U.S. population… National oral prescription drug costs were highest for female breast, leukemia, lung, and prostate cancers” (See this reference) As an aging (rapidly…) man myself, I can only hope we are able to fall back on the precepts taught in Sir William Osler’s essay, “Aequanimitas“, combining the qualities of “imperturbability” and “equanimity” to achieve “”coolness and presence of mind under all circumstances”. If so, we should be able to navigate the avalanche of medical knowledge and associated costs with compassion, empathy, and wisdom. Meanwhile, hats off to the researchers and men who participated in clinical trials and brought this advance and many others you can see here to fruition.
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Remarkably, estrogen was discovered to be a cancer driver for breast cancer by surgeons in the late 1800’s but it was 5 decades before the relationship of hormones to prostate cancer was discovered. George Beatson had considered performing oophorectomy for women with breast cancer because the procedure was successful in prolonging lactation in cattle. His first patient experienced a complete remission from soft tissue breast ca metastases and lived another 4 years. He later said that he thought this treatment would induce “fatty degeneration” of malignant cells.
The relationship of testosterone as a driver of prostate cancer is credited to Huggins and Hodges, who found that either surgical castration or administration of estrogen to men with prostate cancer could reduce what was then the only known marker of prostate cancer, acid phosphatase. Additionally, if they administered testosterone to these patients, the acid phosphatase would increase. This built on observations that the enzyme was present in the prostate gland and would go up in patients as they developed metastases, usually in the bones. For this work, Huggins was awarded the Nobel prize in 1966. The use of surgical castration or estrogen administration remained the mainstay of treating metastatic prostate cancer until the introduction of leuprolide in the early 1980’s. I had the extraordinary opportunity to participate in those trials, which we published in 1984. We compared leuprolide to DES, an oral form of estrogen that works on the same endocrine axis as leuprolide, causing the pituitary gland signaling hormone, LH to drop, and subsequently the testicles stop making testosterone. Leuprolide worked as well as DES, but oral estrogen is dangerous – leading to blood clots and increased risk for heart attacks or strokes. Thus, leuprolide (and other GnRH analogs…including the recently approved oral GnRH antagonist, relugolix) became the standard for ADT therapy of prostate cancer.
But estrogen still works. In fact, it may have some significant advantages over surgical castration or GnRH therapy. Our team found that DES could still produce meaningful responses in patients with rising PSA’s who had failed GnRH even though we did see blood clots. But, you can also give estrogen via transdermal patches which avoids many of the problems of oral DES. This week, the PATCH trial program in the UK reported the safety results of using estradiol patches (E) to treat prostate cancer patients compared to GnRH agonists. The ability to produce therapeutic (castrate level) testosterone was the same, but the E treated patients had lower cholesterols, lower blood pressure, less diabetic tendencies, and far fewer hot flushes. Previous study analyses have shown that E is better for bone health with no calcium loss. The only thing that was worse was breast enlargement (gynecomastia) which was seen in 86% of E patients compared to 38% in the GnRH agonist patients. To some extent, gynecomastia can be treated by radiating the breast tissue. The efficacy of E in treating the prostate cancer in these patients will be reported in 2023 and 2024. The cost of E treatment (4x .025mg/24h patches every 3.5 days) is about $62/week ($750/3 months) which is definitely less than any of the GnRH agonists or antagonists. It will be terrific if this “old fashioned” treatment can again join the treatment options for men with advanced prostate cancer. I think it would also be reasonable to try in patients who are failing the newer second generation agents before trying the more expensive/complicated/toxic alternatives like taxane chemotherapy or radionuclide agents (Radium 223, Lu177-PSMA, etc.) With PSA monitoring, it should be relatively easy to find patients who benefit from such treatment.
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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:
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.”