Treating cancer usually means annihilating the cancer cells. Chemotherapy is one way to do this, but a more targeted or localized approach is radiation.
Traditional radiation therapy zeroes in on the DNA of cells with a high-energy X-ray beam to stop cancerous cells from reproducing. This approach can be pretty effective, but it can also harm healthy cells in the process.
It enters the body and passes through tissues, lessening as it goes—and heads straight out the other side.
Conventional radiation therapy poses another problem: Once you’ve been treated with this type of radiation, it’s usually one and done. You can’t go back for a second round.
However, a newer type of radiation called proton therapy uses high-speed proton beams to deliver radiation to cancer cells—without damaging nearby tissue. This creates an added bonus.
“Now with proton therapy—because of its ability to spare normal tissues—we can treat patients a second time and offer them opportunities for survival, getting rid of that tumor where we couldn’t before,” says James Metz, MD, Chair of Radiation Oncology at Penn Medicine.
Dr. Metz explains how proton therapy can give cancer patients with disease recurrence more options.
The Problem with Recurrence
Options are limited for patients who have received conventional radiation but had a local recurrence. That means the cancer came back in or near the same spot, but it didn’t spread.
“In that circumstance, we could do surgery in a very small number of patients, but most really couldn’t get any other localized treatments specifically for that tumor,” explains Dr. Metz.
The problem lies not so much with the tumor itself, but with the normal tissues surrounding it. These tissues have reached their maximum radiation capacity.
But proton therapy allows for a second chance at radiation treatment. Proton therapy’s pencil beam scanning misses those normal tissues. Pencil beam scanning means a beam equal in size to a pencil lead targets a tumor precisely. The beam can be adjusted, so that just the right dose gets distributed.
“We can actually re-treat a patient with the full dose and potentially cure them where we just couldn’t do it before,” says Dr. Metz.
Dr. Metz recalls what it was like for his patients before he began using proton therapy. Treatment for them was incredibly different: They were vomiting, dehydrated, had diarrhea, and they just felt lousy.
When he combined proton-based radiation with conventional chemo, he saw a difference in how well patients tolerated treatments, and how much their quality of life was improved.
“The patient experience is number one to me, how they feel going through treatment,” Dr. Metz admits. “And improving on this allows us to do other things that we couldn’t do before when they can tolerate this treatment.”
“We can actually attack the tumor more aggressively without attacking the whole body,” he adds.
The Future for Proton Therapy
Penn Medicine researchers are currently looking at many different disease sites that are being retreated with proton therapy. “And we’re very excited about the outcomes,” Dr. Metz says.
So far, about 170 patients have been treated on this unique clinical trial, and Dr. Metz hopes to see more patients receiving treatment in the future.
Having a team dedicated to this type of research and working in partnership with patients brings hope of a cure for the future.
“Every patient brings something individual to the table,” Dr. Metz says. “It's our job as cancer researchers, as physicians, as your team to pull that out of you and understand how we can tailor our treatments to best fit your individualized situation.”