Stereotactic partial breast radiation is safe, faster than traditional radiation in early breast cancer patients

Compared with traditional radiation, stereotactic partial breast radiation is safe, provides excellent cosmesis, and may decrease treatment time from 6 weeks to just days in patients with early-stage breast cancer who have undergone partial mastectomy, according to results from a recent phase 1 clinical trial published in the May 2017 issue of the International Journal of Radiation Oncology, Biology and Physics.

“Standard breast cancer treatments are delivered daily to the entire breast area over 3 to 6 weeks. We sought to deliver partial breast radiation in a noninvasive way, using precise image-guided stereotactic radiation,” said first author Asal Rahimi, MD, assistant professor, radiation oncology, UT Southwestern Medical Center, Dallas, TX. “Our trial decreased treatment time to just five treatments delivered every other day.”

Dr. Rahimi and fellow researchers conducted this study to assess the tolerability of a dose-escalated, 5-fraction, stereotactic body radiation therapy for partial-breast irradiation (S-PBI) in patients with early-stage breast cancer after they had undergone partial mastectomy.

Their primary objective was to escalate the dose using a robotic stereotactic radiation system to treat the lumpectomy cavity, without exceeding the maximum tolerated dose.

They enrolled 75 patients (mean age: 62 years) with ductal carcinoma in situ or invasive nonlobular epithelial histologies and stage 0, I, or II, and tumor size of less than 3 cm. Patients were started on a dose of 30 Gy in 5 fractions, which was raised by 2.5 Gy total, to a maximum of 40 Gy in 5 fractions.

In all, three grade 3 toxicities and one dose-limiting toxicity occurred. Palpable fat necrosis occurred in 10 patients, 4 of whom were symptomatic.

Cosmesis was scored as excellent or good by physicians in 95.9% of patients at baseline, 100% at 6 months, 96.7% at 12 months, and 100% at 24 months post-S-PBI. Corresponding patient scores for the same periods were 86.5%, 97.1%, 95.1%, and 95.3%, respectively. Thus, disagreement rates between physicians and patients for these periods were 0.4%, 2.9%, 1.6%, and 4.7%.

No recurrences or distant metastases were observed.

Leslie LeBlanc, one of the study participants and Dr. Rahimi's patient, is a dental hygienist in Arlington, TX, diagnosed with early-stage breast cancer at the age of 47, 4 years ago. Her daughter was just starting college and she had a son in high school.

LeBlanc's two sisters had been diagnosed with cancer as well, and she was already enrolled in a UT Southwester risk assessment program. Every 6 months, she had mammograms and MRIs, which helped catch her disease early.

“It was overwhelming to consider doing several weeks of daily radiation while trying to work fulltime, be with my family, and do everything that I needed to do. This treatment option was so much better. I only missed a few days from work,” said LeBlanc, who is looking forward to reaching her 5-year mark as a survivor next year.

“Mrs. LeBlanc is a working woman, a mom, and a wife. She’s a great example of many women that will be impacted by this disease,” said Dr. Rahimi. “We wanted to make this treatment more convenient for patients, because cancer is never convenient.”

Dr. Rahimi and colleagues plan to continue their studies of the partial breast radiation technique.

“As technology improves, we will detect more early-stage breast cancers,” said senior author Robert Timmerman, MD, professor, radiation oncology, UT Southwestern. “Patients with these early cancers might particularly benefit from a local therapy approach that both minimizes the normal tissue exposure while improving the convenience for patients who already lead hectic lives.”

This study was funded by a grant from Accuray, producers of the Cyberknife used to deliver stereotactic partial breast radiation.