Reducing Radiation Exposure With Proton Therapy for Prostate Cancer

Proton therapy for the treatment of prostate cancer gives patients a less harmful approach to radiation by targeting the affected area, an expert said.

Over the years, the indications for proton therapy have been expanding and now included patients with localized tumors in addition to those with lymph node involvement. Although there are a select few centers that offer this treatment option for prostate cancer, its availability may be expanding over time.

CURE® spoke with Dr. Shaakir Hasan, radiation oncologist at the New York Proton Center, to learn more about proton therapy, which patients with prostate cancer may be a good fit for this treatment option and potential side effects.

CURE®: What is proton therapy?

Hasan: Proton therapy is a type of radiation therapy that is used to treat cancers. Now, traditional radiation therapy has been around for a very long time. Proton therapy is a little bit different in that it builds up dose to the target — which is typically the tumor and any disease that might be at risk — but then it does not go beyond the target. Whereas traditional radiation therapy will build up dose to the target and then dissipate beyond the target, it delivers more radiation to the organs at risk around it, because the organs at risk are healthier tissue that's around the tumor that we try to avoid. With protons, we can better avoid those areas because the dose does not get dispersed beyond our target.

How is proton therapy used to treat patients with prostate cancer? Is it meant for all patients with the disease?

It's great for tumors that are next to critical structures, critical organs, organs that we want to preserve and protect. And the prostate is a good example of this because it's right next to the rectum. There's a really thin layer of fascia between the rectum and the prostate, so there's really no separation. The bladder is right on top of the prostate, the small bowel, large bowel, these all surround the prostate gland in the pelvis. And so we really try to avoid hitting those structures with radiation. That's where proton therapy can come in to really help that.

The uses and indications of radiation therapy and proton therapy specifically for prostate cancer have been expanding. It used to be that it was just stage 1, stage 2, so localized tumors that were only on the prostate itself. But now, if you have tumors that are in the lymph nodes, if you have prostate cancer that comes back after surgery, if you have prostate cancer that's even in the bone — so it's metastatic or it's beyond the prostate — proton therapy can be an option.

With this focused approach for radiation, are there fewer side effects?

Preliminary studies have shown that we do have fewer side effects, particularly gastrointestinal side effects with proton therapy when treating prostate cancer. The rectum, the small and large bowel around the prostate are getting less radiation, so it makes sense that you would see a lower side effect profile.

We are continuing to do these studies. We have trials open at the Proton Center and others throughout the country that will better determine exactly what quality-of-life metrics are improved with this, but preliminary data suggest that it is better.

For the most part, as far as side effects go, the vast majority of patients will actually just kind of cruise through treatment and not experience anything different than how they are already were. But there definitely are some patients that will have increased urinary frequency, urgency and a weaker stream because we do cause inflammation of the prostate gland, the urethra goes through the prostate gland, and it's kind of unavoidable to affect this or to irritate this to some extent. But 90% or so of these side effects can be easily managed with simple medicines like Flomax (tamsulosin), ibuprofen. And the vast majority of these cases return to your baseline about a month or so after treatment.

As far as GI side effects that, fortunately, I don't know if it's protons or just our experience so far, but we really don't see that in our prostate patients. We don't see diarrhea, loose stools, rectal bleeding or anything like that. But if you were to see that, a lot of those side effects are pretty (manageable) as well.

Is proton therapy the type of therapy that's offered at all cancer centers?

Unfortunately, it is not offered at every radiation oncology clinic. So you will have to look up where proton centers are available. For example, the New York Proton Center is the only proton center in the state of New York. And while the number of proton facilities is growing, they're still far less in the country compared to traditional radiation oncology clinics.

Do you think its availability is going to increase over time?

I do. If you look at the past 10 years, it's expanded quite a bit. So I do expect more areas to have proton therapy centers.

Is proton therapy typically given in conjunction with other types of therapy?

It can be given a conjunction if you need it. For example, proton therapy, a lot of patients with more advanced disease, high-risk disease also need concurrent hormone therapy, which is to cut off testosterone and that helps treat the cancer, radiosensitizes the cancer. It also helps control micrometastatic disease, if that were to be present. And we certainly can give proton therapy in conjunction with this treatment, if need be.

If you have a not as aggressive cancer, early-stage cancer we think we can cure at a higher rate without the hormonal therapy, then certainly we wouldn't add it. But yes, any type of chemotherapy, hormonal therapy that traditionally would be given with radiotherapy could also begin with proton therapy.

If a patient thinks that this type of therapy might be suitable for them, what type of advice would you give to them?

Explore all your options. If you have a particular cancer, hop on Google and see what the treatment choices are. With prostate cancer, for example, see a urologist, see a radiation oncologist that does CyberKnife, see one that does proton therapy.

You have to understand even though I think all physicians try to be fair with your treatment options and what you have, at the end of the day, if you're trained in a particular field or a particular type of technology, that's what you know. I can't talk to you about surgery, and a urologist can't talk to you about proton therapy. So go out and seek the specialist and gather as much information as you can.

It might be a bit overwhelming, which I understand; a lot of prostate patients have a lot of options. But that's a good thing. It's a good thing to have many options. And unfortunately, a lot of other cancer patients don't have many options. So when you have a lot of good options in prostate cancer, which you do, take your time, figure it out, see what suits you the best, which you're more comfortable with, and then go with that.

This transcript has been edited for clarity and conciseness.

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