Why some one only need 5 sessions? Other need dozens of therapy?

@lifutang, I am a 74 year old prostate cancer patient sorting through the same decisions as you. It sounds like you have an excellent care team that is collecting the necessary information to help you make treatment decisions. You still have a very important diagnostic puzzle piece to collect and consider: metastasis. Your doctors have ordered exactly the right test - a PSMA. Then your treatment team will make definite recommendations. You may or may not choose to get a second opinion at that point, depending on whether you think a second opinion will make you feel more confident in the treatment decisions you need to make to move forward.
My diagnosis came to me December 12th. Like you, once I received the diagnosis of PCa, I wanted to plow ahead as quickly as possible to educate myself and make a treatment decisions ASAP. I found out that most prostate cancers, including mine, progress slowly and I had time to gather information, get second opinions, and educate myself about my treatment options. My educational path led me to explore RARP, all variations of external beam radiation therapy, and combination treatments using some form of EBRT with ADT (Androgen Deprivation Therapy) or brachytherapy. Your post made me count the number of clinical trial reports I've downloaded and reviewed: 62. I've also viewed most every relevant video posted on PCRI.com (Prostate Cancer Research Institute) and read Dr. Patrick Walsh's Guide to Surviving Prostate Cancer. My point is you have time to consider your options.
Until you have the results of the PMSA, what helped me most at your discovery point was Dr. Walsh's book (if you don't already have it) and mixing in some PCRI videos on diagnosis and treatment options for your Gleason stage (8).
After you get your PMSA results, if you're still interested in pros, cons , and side effects of different fractionation schedules of external beam radiation treatment for PCa, check back in on this forum. I've got enough information to put you to sleep and many others on this forum are incredible resources.
Most importantly, know that you have support! There are many people on this forum that have your best interest at heart! God bless!

Tyler, the five fraction treatment is with fairly new technology that combines MRI with Radiation. Because the prostate moves during treatment having imaging concurrent with teatment allows a closer margin. The five is more intense radiation per treatment.
Proton equipmet is not compatible with MRI. If you decide on Proton, you probably have 28 treatments or fractions as they are called.
Most institutions don't have the Linac or MRIdian equipment.
Hormone treatment can dramatically shrink the tumor. And it makes the tumor more susceptible to radiation.
It is often recommended without metastasis.
The case I'm most familiar with was similar to yours. Hormone treatment was two months before 5 fractions with the MRIdian and 2 months following.
You should meet with at least 1 radiation oncologist and one proton radiation oncologist before deciding.
In my opinion the advantages of the five fraction outweighs the advantage of proton. You may have a completely different opinion. Bless your choice with luck.
Ask your urologist to order Decipher or one of the other somatic testing of the dna of the tumor.
https://www.veracyte.com/decipher-prostate/

I had proton radiation therapy at Loma Linda Hospital in Loma Linda, California (near Riverside). This was in 2010. I had radiation each weekday morning for 2.5 months. I understand now, the treatment period is much less. I was Gleason 3+3; PSA: 6.47 with localized slow-growth cancer. There are not that many proton radiation facilities in the US, perhaps eight or 10 at this writing.

If you have the choice both with full coverage insurance or other, I would strongly suggest proton radiation therapy over photon (x-ray) type radiation. Do your research and you will agree. Good luck. RH/Florida

2010-proton radiation at Loma Linda Hospital in Loma Linda, California. Gleason 3+3; PSA: 6.47. Slow growth prostate cancer localized. I spent 2.5 months at Loma Linda every weekday morning for now more than a few minutes for the radiation.

From some research and comments, it appears there are "opinions" relative to smaller doses of radiation over a long period versus larger doses of radiation over a shorter amount of time. 2010 was some time ago, and things changed in terms of technology and research. Of course, a shorter radiation period means less cost; this fact may be a metric in the decision for a longer period of radiation or shorter periods. Many of the proton radiation centers like the one at the University of Florida or other notable proton radiation centers have done thousands of patients. Once your diagnosis is finalized and affirmed, then the issue is matching your situation to the thousands of others using a comparative analysis. This is why the diagnosis of the exact location of the prostate cancer is important. If I recall correctly, a PET scan was done to determine the exact location.
Part of the prep process was a lower body cast is "fix' the lower body for exactness. Then (perhaps the most uncomfortable part), a balloon was placed in the rectum to "fix" the prostate. The exactness of targeting is the objective. The exactness of targeting should be a question for your doctor as he/she explains the steps in the preparation of the proton radiation process. If you decide on a photon (X-ray), the same questions should be asked. In short: "HOW DOES ONE TARGET THE EXACTNESS OF THE CANCER?' Hope this adds to your library of information.

@lifutang
Try to give you, my experience. The number of treatments has changed over the years. You can have high dose radiation and less treatments. Or low dose and extended treatments. The high dose is usually over 5 days where low dose can be 20/30/ or more depending on your R/O.

Your R/O will probably have a preference for high dose or low dose. You also should have the option. The success rate for high dose and low dose is practically the same. What my PCP is passing on is that the statistics are showing an increase in side effects of those getting the high dose.

Regarding proton. All radiation treatments have gone through upgrades and updating. When you hear proton just remember the radiation does enter the body a full dose, releases it's full dose at predetermined spot, AND does not exit body. It is why those who chose proton radiation as it possibly can reduce radiation damage to surrounding organs and tissues as does not exit the body.

When you hear photon just remember enters body full dose, targets the locations set up, AND continues to exit the body. I hope you can see the major difference. Again, the success rate for both is identical.

I had 30 rounds of proton radiation at UFHPTI. It is a medical institution who has been doing proton radiation treatments since 2006 and is ultra-modern. My R/O did not like the high dose reduced number of days. His research and feedback from patients showed a higher rate of increased side effects with high dose 5 day programs. He has done thousands of radiation treatments.

Mayo Jacksonville did not have proton radiation, only photons. They wanted to do 20 rounds of radiation using SBRT. I chose proton at UFHPTI as any chance to reduce radiation damage to surrounding organs and tissues I wanted to do.