The American Society of Radiation Oncology (ASTRO) recently issued new guidelines for the appropriate use of partial breast irradiation (PBI) for patients receiving treatment for ductal carcinoma in situ (DCIS) and early-stage invasive breast cancer. The recommendations were published in Practical Radiation Oncology.
Breast cancer remains the leading cause of global cancer incidence, with approximately 2.3 million new cases diagnosed in the year 2020. PBI can serve as an alternative to whole breast irradiation (WBI) for select patients, but guidelines recommending its use have not been formally enumerated.
ASTRO convened an expert panel that included medical, surgical, and radiation oncologists who treat patients with breast cancer in the academic and community settings, as well as a patient representative and a medical physicist. The American Society of Clinical Oncology and the Society of Surgical Oncology collaborated with ASTRO to formulate the guidelines, which were peer-reviewed by 17 experts prior to publication.
Members of the expert panel conducted a search of medical databases and identified 23 studies for inclusion in their literature review. The included studies considered PBI in adult female patients diagnosed with DCIS or early-stage invasive breast cancer, with data regarding ipsilateral breast recurrence, overall survival, and safety.
The panel issued four recommendations for patients with early-stage invasive breast cancer and three recommendations for patients with DCIS. They issued a strong recommendation for PBI for patients with grade 1 or grade 2 disease, ER-positive histology, age 40 years or older, and tumors 2 cm or smaller in size.
In addition, they conditionally recommended PBI for patients with grade 3 disease, ER-negative histology, or tumors between 2 to 3 cm in size. “PBI may not be appropriate when multiple of these factors are present, given the possibility of a higher recurrence risk,” they wrote.
PBI was conditionally not recommended for patients with HER2-positive tumors who are not receiving anti-HER2 therapy, patients with lymphovascular invasion, and patients with lobular histology. Based on expert opinion, it was not recommended for those with positive lymph nodes, positive surgical margins, BRCA1/2 mutations, and among those aged younger than 40 years.
For patients with DCIS, PBI was strongly recommended for patients with low-to-intermediate grade disease, who are aged 40 years or older, and have tumors 2 cm or smaller in size. It was conditionally recommended for patients with high grade disease or tumors between 2 to 3 cm in size. However, they cautioned that WBI may be more appropriate when both of these factors are present.
PBI was not recommended for patients with DCIS and positive surgical margins, known BRCA1/2 mutations, and among those aged younger than 40 years. In terms of PBI techniques, the panel strongly recommended 3-dimensional conformal radiation therapy, intensity-modulated radiation therapy, and multicatheter brachytherapy. Single-entry catheter brachytherapy was conditionally recommended.
The panel did not recommend electron intraoperative radiotherapy for patients with early-stage invasive breast cancer, except in patients enrolled in a clinical trial or registry. They also did not recommend kilovoltage intraoperative radiotherapy for patients with DCIS, except as part of a clinical trial.
The recommended fractions for patients receiving external beam irradiation were 300 cGy in 5 once-daily fractions, given on nonconsecutive days within 2 weeks. Alternatively, 4,005 cGy in 15 once-daily fractions over 3 weeks was also recommended. “For patients … receiving PBI with high-dose-rate brachytherapy, 3,010 cGy in 7 fractions, 3,200 cGy in 8 fractions, 3,400 cGy in 10 fractions delivered twice daily or 5,000 cGy with 160-180 cGy/hour pulsed-dose-rate is recommended,” the panel wrote.
In order to minimize toxicities, the panel recommended once-daily external beam PBI. This schedule was also associated with better cosmetic outcomes. The panel also recommended multicatheter brachytherapy and noted that PBI was preferable to WBI in patients eligible for an intended dose of 4,005 cGy in 15 fractions.
The panel did not recommend twice-daily external beam radiation, citing the potential for adverse cosmetic factors. “Multiple randomized controlled trials, enrolling over 10,000 patients, have demonstrated oncologic equivalence between PBI and WBI for the treatment of early-stage invasive breast cancer and DCIS,” the panel concluded.
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Disclosures: Some members of the expert panel declared financial ties to drugmakers. See the full study for details.
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