Proton Therapy: 5 Signs Cancer Care Is Rapidly Evolving


Radiation therapy today is nothing like it was two generations ago.

If you have cancer, you’ll be on the receiving end of a machine that’s three stories tall. The machine features an enormous rotating platform called a gantry that receives accelerated protons from a cyclotron.

It’s designed to deliver a lightning-fast proton beam straight to your tumor, destroys the DNA of cancer cells, but leaves healthy cells virtually untouched.

Remember the Star Wars’ Death Star? It works something like that.

Welcome to the Future

It’s perfunctory, precise and painless. While you lie on a bed, a 33-foot high, 100-ton gantry spins around you to target the tumor. Total time: 30 minutes.

No, this is not a sci-fi flick. This is the future of cancer treatment. It’s called proton therapy. The treatment arrived at Penn Medicine in 2010 and continues to evolve—rapidly.

“Conventional radiation has kind of hit its limit because there’s only so much it can do from a physical standpoint,” explains James Metz, MD, professor and chair of Radiation Oncology at Penn Medicine and executive director of OncoLink. “Whereas with proton work, you’re going to see the continued evolution of proton technology over the coming years.”

image of proton therapy machine and some facts about it

Here are the top five ways proton beam therapy has evolved since its arrival at Penn Medicine.

Pencil Beam Scanning

Past radiation techniques hit large areas of tissue, including healthy tissue.

Over time, Penn has added pencil beam scanning, which is a more precise beam for targeting tumors.

“It’s exactly the size of pencil lead,” Dr. Metz explains. “We use magnets to steer it, so it’s basically spot-by-spot. We can be very, very specific.”

Because the beam is so targeted, with less exposure to healthy tissue, harmful side effects and complications are reduced considerably.

Two-thirds of Penn’s patients are now treated with pencil beam scanning.

Changes in Imaging

When Penn Medicine’s Roberts Proton Therapy Center first opened, radiation oncologists used x-rays to look at bony anatomy, but they had to manually place markers in soft tissue.

“Now, we’re using cone beam CT (computed tomography), which allows us to look at soft-tissue imaging, and is important for targeting areas like the abdomen and the chest,” Dr. Metz says.

With cone beam CT, the team can assess changes in anatomy over the course of treatment to detect when tumors grow and recede. Based on that, the treatment plan can be changed when necessary. Treatment usually takes place five days a week over several weeks.

“We launched that back in September of 2014. We’re still the only center in the world using that technology,” says Dr. Metz.

Handling Positioning and Motion

Even though a typical treatment is 30 minutes, it only takes two minutes to deliver the proton beam.

The rest of the time is spent making sure the patient is positioned exactly right. “This beam is within less than a millimeter of accuracy,” Dr. Metz explains. Even the slightest movement can mean the radiation hits the wrong tissue.

“For instance, when you breathe, things move on the inside,” says Dr. Metz. “When you have a very specific target, how do you make sure things haven’t moved from where you thought they were?”

“We use special technology to manage that motion,” he explains. “We still have a ways to go, but as we continue with other developments, that area moves pretty rapidly.”

Expanded Opportunities for Treatment

Since its opening, the Roberts Proton Therapy Center has expanded into treatment for other diseases.

“We started with prostate, but we wanted to go into other disease sites,” Dr. Metz says. “Today, only 15 percent of our patient volume is prostate cancer, and 85 percent is other things.”

Proton therapy has also allowed Penn to treat patients who couldn’t be treated before, including cancer patients who had normal tissue exposure from previous radiation and couldn't receive more radiation treatment, Dr. Metz explains.

“We’ve been treating numerous patients who have had cancer recur in various ways, and we’re very excited with the results,” he says.

Ability to Treat Large Numbers of Patients at a Time

The Center’s ability to treat more patients has evolved over the last five years. It began with one treatment room and expanded to five shortly thereafter.

“We went from treating a small number of patients a day to around 100 patients a day on protons,” Dr. Metz says. “We also have a large conventional facility that’s integrated with conventional radiation treatment and treat around 135 patients a day with that. So, we have around 235 patients coming through the facility each day.”

All patients are treated on clinical trials, and the Center currently has about 20 in progress.

The Road Ahead

“It's very clear that proton therapy is going to emerge as a great opportunity for combining with chemotherapy, biological agents and surgery in ways that we just couldn’t do before,” Dr. Metz says. “We’re very excited where the future is with this. The sky’s the limit.”

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The Focus on Cancer blog discusses a variety of cancer-related topics, including treatment advances, research efforts and clinical trials, nutrition, support groups, survivorship and patient stories.

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