Tucked in a corner of the MedStar Georgetown University Hospital campus is the country’s 28th proton therapy center, which treated its first patient on March 29. It is a small but state-of-the-art system designed to attack tumors more quickly than its predecessors in proton therapy, a precise type of radiation treatment that spares healthy tissue.

Proton therapy centers operating in the United States

MedStar Georgetown

WASHINGTON

D.C.

VIRGINIA

1 MILE

The proton therapy center at MedStar Georgetown takes up three floors in a four-story wing. The top floor is office space.

MedStar

Georgetown

WASHINGTON

D.C.

Arlington

VIRGINIA

Proton therapy centers operating in the United States

1 MILE

The proton therapy center at MedStar Georgetown takes up three floors in a four-story wing. The top floor is office space.

MedStar

Georgetown

WASHINGTON

D.C.

Arlington

VIRGINIA

Proton therapy centers operating in the United States

1 MILE

The proton therapy center at MedStar Georgetown takes up three floors in a four-story wing. The top floor is office space.

Twenty-four more centers are under construction or in development, including one at D.C.’s Sibley Memorial Hospital that is scheduled to open in late 2019 and one at the Inova Schar Cancer Institute in Fairfax that is scheduled to open by 2020.

How it works

All types of radiation treatments break the DNA in cells, which makes it harder for them to multiply. Rapidly dividing cancer cells are particularly susceptible to this kind of damage, so tumors often shrink or disappear.

Radiation treatments damage the DNA of cancerous cells to destroy tumors.

Radiation treatments damage the DNA of cancerous cells to destroy tumors.

Radiation treatments damage the DNA of cancerous cells to destroy tumors.

The difference between traditional radiation and proton therapy is in how the radiation is delivered.

Traditional therapy irradiates tumors with X-ray waves, which are beams of photons, and all tissue along the beams’ paths get a similar dose of radiation.

Proton therapy uses beams of protons, charged subatomic particles that can be controlled with magnets. A small amount of radiation is deposited on the way into the body, most goes directly into the tumor and none passes through the other side.

That means, for instance, that radiation aimed at a tumor in one side of the brain wouldn’t harm the healthy side. And a beam aimed at a spinal tumor wouldn’t reach the heart or lungs behind it.

TRADITIONAL RADIATION THERAPY

A beam of photons is aimed at the tumor.

Amount of

radiation

LESS

MORE

The beam irradiates all tissue along its path relatively equally, including healthy tissue behind the tumor.

PROTON BEAM THERAPY

Amount of

radiation

A beam of protons is aimed at the tumor.

LESS

MORE

The beam, controlled by magnets, deposits most of the radiation at the tumor site without affecting most of the tissue behind it.

TRADITIONAL RADIATION

THERAPY

PROTON BEAM

THERAPY

A beam of photons is aimed at the tumor.

A beam of protons is aimed at the tumor.

Tumor

Tumor

The beam irradiates all tissue along its path relatively equally, including healthy tissue behind the tumor.

The beam, controlled by magnets, deposits most of the radiation at the tumor site without affecting most of the tissue behind it.

Amount of radiation

LESS

MORE

TRADITIONAL

RADIATION THERAPY

PROTON

THERAPY

A beam of photons is aimed at the tumor.

A beam of protons is aimed at the tumor.

Amount of

radiation

LESS

Tumor

Tumor

The beam irradiates all tissue along its path relatively equally, including healthy tissue behind the tumor.

The beam, controlled by magnets, deposits most of the radiation at the tumor site without affecting most of the tissue behind it.

MORE

TRADITIONAL

RADIATION THERAPY

PROTON

THERAPY

A beam of photons is aimed at the tumor.

A beam of protons is aimed at the tumor.

Amount of

radiation

LESS

Tumor

Tumor

The beam irradiates all tissue along its path relatively equally, including healthy tissue behind the tumor.

The beam, controlled by magnets, deposits most of the radiation at the tumor site without affecting most of the tissue behind it.

MORE

“You can deliver a high dose to where you need it and spare normal tissues with fewer side effects,” said Anatoly Dritschilo, chairman of radiation oncology at Georgetown.

Because more radiation reaches the tumor, a smaller overall dose is required.

Creating and shaping the beam

The compact proton therapy system at MedStar Georgetown spins protons in a 15-ton accelerator called a cyclotron and releases them when they reach two-thirds the speed of light. This circular system takes up much less space than other types of proton accelerators, which propel protons through long, linear pathways at facilities the size of football fields.

If you visit the treatment room, you’ll notice a loud hum. That’s the cryocooler, which keeps the superconducting magnet at -452 degrees Fahrenheit.

Georgetown’s new wing is 9,300 square feet, far smaller than many other facilities, because its cyclotron proton accelerator is more compact.

Third floor:

Open space lets

the cyclotron

move around

the patient.

Second floor:

Waiting area and

treatment room

First floor:

A concrete

bunker contains

the footings.

Counterweight

Gantry-mounted proton accelerator can rotate 190 degrees.

PROTON ACCELERATOR

Alternating electric fields accelerate the protons in larger and larger circles.

Proton

beam

Magnets steer and focus the protons into a beam.

Gantry-mounted proton accelerator can rotate 190 degrees.

Third floor:

Open space lets

the cyclotron

move around

the patient.

Second floor:

Waiting area

and treatment

room.

First floor:

A concrete

bunker contains

the footings.

Counterweight

Georgetown’s new wing is 9,300 square feet, far smaller than many other facilities, because its cyclotron proton accelerator is more compact.

PROTON ACCELERATOR

Alternating electric fields accelerate the protons in larger and larger circles.

Electromagnets steer and focus the protons into a beam.

Proton

beam

PROTON ACCELERATOR

Third floor:

Open space lets

the cyclotron

move around

the patient.

Alternating electric fields accelerate the protons in larger and larger circles.

Gantry-

mounted proton accelerator can rotate 190 degrees.

Second floor:

Waiting area

and treatment

room.

Proton

beam

Electromagnets steer and focus the protons into a beam.

First floor:

A concrete

bunker contains

the footings.

Counterweight

Georgetown’s new wing is 9,300 square feet, far smaller than many other facilities, because its cyclotron proton accelerator is more compact than traditional beam-line accelerators.

PROTON ACCELERATOR

Third floor:

Open space lets

the cyclotron

move around

the patient.

Inside, a ring of alternating electric fields accelerate protons.

Gantry- mounted proton accelerator can rotate 190 degrees.

Second floor:

Waiting room

and treatment

room

Proton

beam

Electromagnets steer and focus the accelerated protons into a beam.

First floor:

A concrete

bunker contains

the footings.

Counterweight

Georgetown’s new wing is 9,300 square feet, far smaller than many other facilities, because its cyclotron proton accelerator is more compact than traditional beam-line accelerators.

Once the protons reach top speed, they pass through a device that uses adjustable plates to focus the beam and shape it to the contours of the tumor. This is a new version of “pencil-beam” technology that has been used for roughly a decade. Before then, proton therapy scattered protons like water from a fire hydrant, Dritschilo said. Now, the “pencil-beam” is more like an easy-to-aim hose.

Treating the tumor

The beam enters the patient in pulses, irradiating the tumor layer-by-layer, much like a 3-D printer operates.

Patients must hold still for only seconds at a time, compared to minutes for traditional radiation and older versions of proton therapy.

An entire treatment takes just a couple of minutes (plus about 20 minutes to set up the machine). As with other types of radiation, patients go for treatment once a day, five days a week, for five to eight weeks.

Inside

treatment

room

Detail of

adaptive

aperture

below

Metal plates inside the adaptive aperture move back and forth.

The opening that is created focuses the beam to match the contours of the tumor.

Beam

Plates

The beam delivers radiation into the tumor, layer by layer.

Tumor

Metal plates inside the adaptive aperture move back and forth.

Inside treatment room

Detail

Beam

Plates

The opening that is created focuses the beam to match the contours of the tumor.

Adaptive

aperture

The beam delivers radiation into the tumor, layer by layer.

Tumor

Metal plates inside the adaptive aperture move back and forth.

Inside treatment room

Detail

Beam

Plates

The opening that is created focuses the beam to match the contours of the tumor.

Adaptive

aperture

The beam delivers radiation into the tumor, layer by layer.

Tumor

Who benefits?

Children who have cancer may benefit most from proton therapy because more of their normal cells are developing rapidly, making them more prone to damage that could stunt the growth of healthy organs, Dritschilo said. Because of this, most insurance companies cover proton therapy for children.

Other main beneficiaries would be people with tumors in the head, neck and spine, and those who have cancers near other very sensitive organs, such as patients with cancer of the left breast, which is directly over the heart. For others, it could be a quality-of-life issue: a person whose lungs would be so damaged by a bit of extra radiation that they would need an oxygen tank, for example.

Who doesn’t benefit?

For some cancers, less precision is better. Lymphoma treatment, for instance, often requires a wider radius around lymph nodes because of the way the cancer grows and spreads, Dritschilo said. And systemic cancers such as leukemia could not be treated by proton therapy alone.

Many common cancers fall into a gray area, where doctors and patients need to weigh risks, costs and benefits of different types of treatment. That’s where the controversy comes in.

Proton therapy has been controversial when used routinely for some types of cancer, notably prostate cancer, because data comparing patient outcomes with other treatment forms is slim and because it is much more expensive than traditional radiation.

Soon, both those issues may begin to be resolved, said Brian Kavanagh, chairman of the American Society for Radiation Oncology. Several large clinical trials comparing treatment methods should yield solid data in the next couple of years. And, as with all technology that has been around awhile, proton therapy center prices are coming down, and the cost to patients should decline as well.

MedStar Georgetown’s small center, which has one treatment bay, cost $39.7 million including the building. Sibley’s much larger four-bay center will cost at least $157 million, but that is still well below the $200 million to $250 million price tags on centers that were built earlier. Kavanagh said he expects that tech innovations may cut costs by half in the next five or six years.

As proton therapy has become more mainstream, he said, other types of creative radiation technologies have emerged that may prove to be as precise as proton therapy in some cases. These would give doctors more cancer-fighting weapons and patients more choices.

“Competition is a good thing,” Kavanagh said. “The pressure to improve other forms of radiation treatment technology in recent years has led to tremendous innovation all around. Nowadays cancer patients can receive excellent therapy with either proton or non-proton based radiotherapy.”

This story has been updated to include the proton therapy center that is under construction in Fairfax.

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Additional sources: Brian T. Collins, MedStar Georgetown’s Clinical Director of Radiation Medicine; Michael Tajima of Mevion; American Society for Radiation Oncology; Johns Hopkins Medicine National Proton Center at Sibley Memorial Hospital; National Association for Proton Therapy; Map from Maps4News/HERE Originally published March 1, 2018.

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