Can you receive additional proton treatments years after radiation?

@surftohealth88 Actually, both “radiation is radiation” and “many side effects are seen years down the road” need further explanation.

Photons and protons are as different as night and day.
> photons are massless packets of electromagnetic energy (like X-rays); photons lose energy continuously along their entire path.
> protons are heavy, positively charged subatomic particles; protons travel a specific distance, then create an intense burst of energy right at the end of their path.

The practical application of these concepts is significant.
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As for “many side effects are seen years down the road” —> Remember that what radiation doesn’t hit, it won’t affect. Much planning should be taken not to overshoot the prostate in order to avoid hitting nearby otherwise healthy tissues and organs (i.e., minimize entry-dose, scatter, and exit-dose). By applying radiation precisely and accurately, there should be no side effects seen years down the road.

@brianjarvis
Large comparative studies did not find it to be the case for prostate cancer , I do not have links handy since I was exploring the subject last year. The SA were similar for urinary and rectal SA - there was no big significant difference.
BUT, I am glad you had Proton and had great results - may it stay that way forever 🍀😊 !

Below is an article I get from a site that sends me frequent medical information. It about Proton Therapy. In a nutshell they say: For prostate cancer, however, the most important question has never been whether proton therapy is technologically impressive.

The question is whether patients experience better outcomes.

The latest evidence suggests that for most men with low- and intermediate-risk localized prostate cancer, the answer is probably no.

It's pretty long and most way over my head, but some might find it interesting??
https://www.medscape.com/s/viewarticle/proton-therapy-prostate-cancer-what-should-clinicians-do-2026a1000m94

@surftohealth88 The two studies that are usually referenced are COMPPARE and PARTIQoL.
> COMPPARE: https://ascopubs.org/doi/10.1200/JCO.2026.44.17_suppl.LBA5012

> PARTIQoL: https://ascopost.com/issues/april-25-2025/proton-therapy-and-intensity-modulated-radiation-therapy-for-localized-prostate-cancer/

Both studies indicated similar tumor control rates and patient-reported quality of life outcomes between photon and proton radiation for prostate cancer.

What’s important to understand about clinical trials is that they’re great at providing a “big picture” view of what to expect from treatments. Since they represent thousands of patients, insurance companies need that, hospitals need that, governments need that, etc., because they all need to plan “big” and estimate how to allocate resources (dollars, equipment, staffing, etc.) based on the averages……not the best; not the worst.

But for what a specific patient (you or me) should expect our individual outcome should be from a particular treatment, they’re nearly worthless - without knowing how someone with my (or your) specific diagnosis, risk factors, comorbidities, strict regimen compliance, etc. compares to ours. (And that applies to all clinical trials, not just these two.) “Averages” aren’t what’s important.

@robertov What external radiation (both photon and proton) does is to damage DNA at the cellular level. (See attached graphic.)

External radiation doesn’t simply “radiate the prostate,” it damages cellular DNA which prevents prostate cancer cells from multiplying. Cancerous prostate cancer cells do not have healthy DNA repair mechanisms, and over time they die off (which we observe as PSA decreasing).

Non-cancerous prostate cells are damaged as well, but they have healthy DNA repair mechanisms and can (usually) repair the radiation-induced DNA damage. They survive external radiation treatments and continue producing PSA (though at low “new normal” levels).

This also is why it’s helpful to maintain hormone therapy for some time after radiation treatments have ended. Radiation damage to prostate cancer cells’ DNA can continue long after the radiotherapy itself has been completed. So by keeping the androgen receptors inhibited or suppressed by hormone therapy, you can suppress that DNA repair mechanism for months. This is why ADT is a very important component to kill prostate cancer cells.

Thanks @brianjarvis. I guess I ‘knew’ that, but it still is confusing to me. Is it all prostate cells that are radiated? Can’t be just the surface ones. Does it operate from lower cells upwards. I understand about DNA repair mechanism differences, although it seems far too convenient.

Thanks @surftohealth88 for also responding.