New ASTRO Guidelines Recommend Partial Breast Irradiation for Early-Stage Breast Cancer

The guidelines recommend that, for patients with early-stage, node-negative invasive breast cancer with favorable clinical features and tumor characteristics, PBI is the recommended treatment option over WBI.

New clinical guidelines outline the benefits in performing partial breast irradiation (PBI) as opposed to whole breast irradiation (WBI) in patients with early-stage breast cancer or ductal carcinoma in situ (DCIS), according to a press release by the American Society for Radiation Oncology (ASTRO).¹

Findings from the research, which included data from several published trials, show that there is negligible difference in the risk of ipsilateral breast recurrence (IBR), overall survival, and cancer-free survival in patients who receive PBI compared with those who receive WBI. PBI is also associated with fewer acute adverse effects (AEs) and financial toxicities.

“There have been more than 10,000 women included in these randomized controlled trials, with 10 years of follow-up showing equivalency in tumor control between partial breast and whole breast radiation for appropriately selected patients,” Simona F. Shaitelman, MD, EdM, vice chair of the guideline task force and a professor of breast radiation oncology at The University of Texas MD Anderson Cancer Center in Houston, said in the press release. “These data should be driving a change in practice, and partial breast radiation should be a larger part of the dialogue when we consult with patients on decisions about how best to treat their early-stage breast cancer.”

Researchers assessed 23 trials to determine the effectiveness of a PBI compared with a WBI.² These included 14 randomized control trials (RCT), 6 comparative observational studies, and 3 single-arm observational studies.

The study consisted of 4 key questions used to assess the appropriate uses for PBI as an alternative to WBI to demonstrate similar rates of IBR and toxicity outcomes. These questions included the following:

1. In adult patients with early-stage invasive breast cancer or DCIS, what are the appropriate indications for PBI as an alternative to WBI?
2. In adult patients with early-stage invasive breast cancer or DCIS receiving PBI, what are the appropriate PBI techniques with respect to IBR outcomes?
3. In adult patients with early-stage invasive breast cancer or DCIS, what are the appropriate dose-fractionation regimens, target volumes, and planning parameters for PBI?
4. In adult patients with early-stage invasive breast cancer or DCIS receiving PBI, what are the appropriate PBI techniques with respect to toxicity and cosmesis?

The guidelines recommend that, for patients with early-stage, node-negative invasive breast cancer with favorable clinical features and tumor characteristics, PBI is the recommended treatment option over WBI. These include patients with grade 1 and 2 disease, estrogen receptor (ER)-positive status, and small tumor size, or who are at least 40 years of age. Conditional recommendation is given to patients who have higher recurrence risk, grade 3 disease, ER-negative histology, and a larger tumor size.

However, PBI is not recommended for those who have lymph nodes, positive surgical margins, or germline BRCA1/2 mutations, those who are younger than 40 years of age, or those who have less favorable risk features, namely due to the lack of published data favoring PBI for this population. These recommendations are the same for patients with DCIS.

The guidelines also outline the recommendations for treatment techniques. These include 3-D conformal radiation therapy (3-D CRT), intensity-modulated radiation therapy (IMRT) and multi-catheter interstitial brachytherapy for PBI. Conditional recommendation is given to single-entry catheter brachytherapy, and no recommendation is given to intraoperative radiation therapy (IORT) techniques without whole breast irradiation.

Further research is needed to assess the benefits of PBI in patients withvarious clinical and tumor characteristics and to determine the optimal radiation treatment dose and technique for this treatment type.

References

1. ASTRO issues patient-centered clinical guideline on partial breast irradiation for early-stage invasive breast cancer and DCIS. American Society for Radiation Oncology. News release. November 15, 2023. Accessed December 4, 2023. https://tinyurl.com/3ekcf8dv
2. Shaitelman SF, Anderson BM, Arthur DW, et al. Partial breast irradiation for patients with early-stage invasive breast cancer or ductal carcinoma in situ: An ASTRO clinical practice guideline. PractRadiat Oncol. 2023;doi:10.1016/j.prro.2023.11.001