Proton therapy for treating breast cancer: an effective alternative for some patients

Proton therapy provides a safer, targeted alternative to conventional radiation for some breast cancer patients.

Radiation therapy has improved dramatically over the past few decades to allow for more precise treatment and reduced risks. Proton therapy, a targeted, more accurate form of radiation, is taking medicine on another leap forward.

Seattle Cancer Care Alliance (SCCA) is one of only 39 facilities in the U.S. to offer proton therapy. Located on UW Medicine’s Northwest Campus, SCCA’s Proton Therapy Center is the only facility within an 800-mile radius of Seattle to provide this advanced technology for eligible patients with breast cancer.

“Proton therapy is an excellent tool to have in our radiation oncology toolbox," says SCCA radiation oncologist Dr. L. Christine Fang, who is among a select group of specialists with expertise in using proton therapy to treat breast cancer. “Its superior specificity is extremely helpful when we need enhanced accuracy. We work closely with referring providers to deliver coordinated care and to ensure it is an appropriate treatment option.”

Fang, MD
L. Christine Fang, MD

How proton therapy works

SCCA’s state-of-the-art cyclotron uses an alternating magnetic field to accelerate protons from hydrogen gas into a narrow beam. This proton beam delivers a sharply focused dose of charged particles at a set tissue depth, then loses its energy rapidly. This process destroys cancer cells while surrounding, healthy tissue receives less exposure than with conventional radiation.

Eligibility for proton therapy to treat breast cancer

Proton therapy involves daily treatment over a period of five to seven weeks. A patient may be eligible for this treatment if their history includes:

  • Node positive, non-metastatic breast cancer (either right or left side)
  • A history of prior breast irradiation
  • Complex anatomy or any other factor that makes it challenging to develop a safe plan using conventional radiation

About 30 to 40 percent of Dr. Fang’s breast cancer patients receive proton therapy. Most have lymph node involvement.

“Once we need to include the lymph nodes as part of the radiation, the plan becomes more complex,” says Dr. Fang. “And that's where proton therapy shines. Proton therapy can also be very useful in patients with unique anatomy such as severe scoliosis or other upper body deformities.”

Treating breast cancer with proton therapy

Conventional radiation therapy is an important component of breast cancer treatment. But   excess radiation exposure to the heart during treatment can increase the risk of ischemic heart disease.

One study followed 2,168 women who received radiation therapy for breast cancer between 1958 and 2001. It found a 7.4% increase in major coronary events per every 1 gray (Gy) increase in mean radiation dose to the heart.

Because of its precision, proton therapy has emerged as an alternative to photon radiation for select patients. Early results from an observational study show that proton therapy:

  • Delivers heart-sparing doses of radiation
  • Offers excellent overall breast cancer survival rates
  • Has an acceptable toxicity profile

Randomized clinical trial evaluating proton therapy vs. photon therapy

Questions about proton therapy remain, however. Doctors know that proton therapy effectively treats breast cancer and delivers a lower dose of radiation to the heart, lungs and surrounding tissues. "What we don’t know yet is whether that translates to fewer cardiac events and other long term side effects compared with patients who undergo conventional radiation therapy,” says Dr. Fang.

To help answer that question, SCCA is participating in a pivotal clinical trial (RADCOMP, (NCT02603341). The study directly compares long-term cardiovascular outcomes of women with breast cancer who received proton vs. photon therapy.

Researchers have enrolled more than 1,000 women since the clinical trial started in 2016. All of the participants have non-metastatic breast cancer with lymph node involvement.

“It’s a robust study that should help guide future use of proton therapy for breast cancer.”
— Dr. Fang

Proton therapy treatment and support at SCCA

Patients who may be eligible for proton therapy receive comprehensive care and support from SCCA. Dr. Fang first reviews all provider referrals and schedules an initial consultation. After the visit, she communicates her findings to the referring provider via phone or a consult note.

“For complex cases, the referring providers and I collaborate to make sure everyone is on the same page. This ensures the patient receives the best care possible," she says.

SCCA's support also extends to assisting in the process to obtain insurance approval for treatment. Insurance coverage can be a barrier to accessing proton therapy. Medicare covers proton therapy for breast cancer, but some private insurers do not. SCCA patient financial services staff will process appeals on patients’ behalf.

"Patients should know that even if their insurance company initially denies coverage, our team works hard to get those denials overturned," says Dr. Fang.

For those travelling from out of town, the SCCA team also helps patients find:

  • Additional medical care for non-cancer-related health conditions
  • Lodging and transportation
  • Services and activities in the Seattle area

Learn more about SCCA’s Proton Therapy Center. To speak with a patient care coordinator, call 844.675.1627 Monday through Friday 8 a.m. to 5 p.m. PST. 

To refer a patient, return a Physician Referral Form or call 1.888.987.7782.

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