In terms of initial treatment decisions, a biopsy result with any amount of Gleason 8 guides to treating Gleason 8 PCa.

As to whether the initial treatment is RP or RT, I encourage you to only consider data for the treatment techniques available today and the quality of the team providing the treatment. There are many studies based upon 10 year old data.

For RP, the data today shows that a radical prostatectomy performed by a surgeon that has performed 500+ procedures at a recognized PCa center of excellence has better outcomes in terms of continence and ED (assuming age and pre-existing conditions constant).

For radiation based treatments, the precision of the newest generation equipment used by an experienced team at a PCa center of excellent results in far less biological damage to surrounding tissue, which also affects longer term continence, ED, bladder, and rectum issues. I believe that @bens1 provides the best guidance on precision MRI guided radiation therapy options.

Both of these initial treatments, if all PCa cells are confined to the prostate, can lead to a cure.

If a RP is performed per above, you will have more information after the procedure and within 12 weeks as to whether of not there is a higher probability that all PCa cells were confined to the prostate, both from the post RP pathology report and the initial usPSA test. If PCa is subsequently detected, salvage radiation is the typical secondary treatment.

If the initial treatment is a RT per above, it will take more time for you to know if there is a higher probability that all PCa cells were confined to the prostate, as your post treatment PSA values will decrease over time to a nadir and then measured over time. If a subsequent rising PSA value indicates a biological recurrence, secondary treatment options depend upon PSMA scan results.

And these secondary treatment option specifics are being updated every year and I believe that @jeffmarc provides the best overview of up to date options at all stages of treatments.

My personal opinion only as a fellow PC patient.