When would you administer a radiation boost in breast radiotherapy?

From the Guidelines

A boost in breast radiotherapy is recommended for patients with higher-risk characteristics, such as age <50 years, high-grade disease, or focally positive margins, to reduce local relapse, and is typically administered as 10-16 Gy in 4-8 fractions following whole breast irradiation. The decision to give a boost should be based on individual patient risk factors, including age, tumor grade, and surgical margin status. According to the NCCN guidelines 1, a boost to the tumor bed is recommended in patients at higher risk, and can be achieved with brachytherapy or electron beam or photon fields. The rationale for boost radiation is that the highest risk of local recurrence is at the original tumor site, and randomized trials have demonstrated that a boost reduces local recurrence rates, particularly in higher-risk patients.

Some key points to consider when deciding whether to give a boost in breast radiotherapy include:

• Patient age: younger patients (<50 years) are at higher risk of local recurrence and may benefit from a boost 1
• Tumor grade: high-grade tumors are associated with a higher risk of local recurrence and may benefit from a boost 1
• Surgical margin status: patients with positive or close surgical margins are at higher risk of local recurrence and may benefit from a boost 1
• The boost can be delivered using various techniques, including electron beam therapy, photon therapy, or brachytherapy, depending on the tumor bed location and depth 1

It's worth noting that while a boost may reduce the risk of local recurrence, it may also increase the risk of fibrosis and affect cosmetic outcomes, so the decision should balance recurrence risk against potential side effects. The most recent and highest quality study 1 supports the use of a boost in breast radiotherapy for patients with higher-risk characteristics.

From the Research

Indications for Boost Irradiation in Breast Radiotherapy

• The decision to give a boost in breast radiotherapy depends on various factors, including the patient's age, tumor size, margin status, and risk of local recurrence 2.
• Patients at high risk of local recurrence, such as those with close margins, extensive intraductal component, or triple-negative phenotype, may benefit from a boost dose 2.
• The GEC-ESTRO Breast Cancer Working Group recommends three categories for patient selection for boost irradiation: low-risk, intermediate-risk, and high-risk groups 2.

Benefits and Risks of Boost Irradiation

• Boost irradiation can improve local control and reduce the risk of ipsilateral breast tumor recurrence, especially in young patients 3, 4.
• However, boost irradiation may also increase the risk of moderate to severe fibrosis and worsen cosmetic outcomes 3, 4.
• The benefits and risks of boost irradiation should be carefully weighed, and the decision to administer a boost dose should be individualized based on patient characteristics and tumor factors 2, 5.

Techniques and Dosing for Boost Irradiation

• Various techniques, including photon and electron beam therapy, can be used for boost irradiation 6.
• The optimal dose and fractionation schedule for boost irradiation are still being studied, but doses ranging from 10-16 Gy EQD2 are commonly used 2, 5.
• Simultaneous integrated boost radiotherapy may be a safe and effective alternative to sequential boost therapy, reducing treatment duration and potentially minimizing toxicity 5.