What is the prime study regarding radiation therapy in breast cancer after lumpectomy (limited surgical removal of a tumor)?

From the Guidelines

Whole breast irradiation is strongly recommended after lumpectomy for patients with node-positive disease, and is also recommended for those with negative axillary nodes, as it reduces the risk of local recurrence and improves overall survival. This recommendation is supported by the results of a meta-analysis by the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) showing reduction in 10-year risk of recurrence in those who received whole breast irradiation versus those who did not (19% vs 35%; relative risk [RR], 0.52; 95% CI, 0.48–0.56) 1.

Key Points

• Whole breast irradiation reduces the risk of local recurrence and has a beneficial effect on survival
• An additional boost dose of radiation to the tumor bed can further decrease in-breast recurrences
• The panel recommends whole breast irradiation to include breast tissue in entirety, with CT-based treatment planning to limit irradiation exposure of the heart and lungs
• Radiation boost treatment can be delivered using enface electrons, photons, or brachytherapy

Radiation Therapy Considerations

• The use of compensators such as tissue wedges, forward planning using segments, and IMRT may be used for greater homogeneity of target dose and to spare normal tissues
• Respiratory control techniques, including deep inspiration breath-hold and prone positioning, may be used to further reduce dose to adjacent normal tissues
• The NCCN panel recommends doses of either 45 to 50 Gy in 23 to 25 fractions or 40.0 to 42.5 Gy in 15 to 16 fractions for whole-breast radiation 2

Patient Selection

• Patients with node-positive disease should receive whole breast irradiation, while those with negative axillary nodes may also benefit from radiation therapy
• The decision to use radiation therapy should be individualized based on patient factors, including age, tumor size, and presence of lymphovascular invasion 3

From the Research

Radiation Therapy in Breast Cancer after Lumpectomy

• Radiation therapy is a standard treatment for early-stage breast cancer after lumpectomy, with whole breast radiation therapy (WBRT) being the most common approach 4, 5, 6, 7.
• Studies have compared different radiation therapy techniques, including conventional WBRT, accelerated partial breast irradiation (APBI), and accelerated whole breast irradiation (AWBI) 4, 5, 7.
• A study published in 2020 found that hypofractionation (HFRT) had higher completion rates compared to standard fractionation (SFRT) 4.
• Intraoperative radiation therapy (IORT) has also been explored as a technique for delivering a single dose of radiotherapy at the time of surgery for early-stage breast cancers, with promising results 8.

Comparison of Radiation Therapy Techniques

• A 2021 Cochrane review compared partial breast irradiation (PBI) or APBI with WBRT and found that local recurrence-free survival was probably slightly reduced with PBI/APBI, but overall survival was similar 7.
• The review also found that cosmesis was probably worse with PBI/APBI, and late radiation toxicity was probably increased 7.
• A 2015 study found that a radiation boost after WBRT had no effect on long-term overall survival, but improved local control, with the largest absolute benefit in young patients 6.

Predictors of Radiation Therapy Completion

• A 2020 study found that African-American and Caucasian patients treated with SFRT versus HFRT had higher odds of not completing radiation therapy 4.
• The study also found that patients residing more than 10 miles from a treatment facility had lower odds of completing radiation therapy 4.