Boost Dose During Accelerated Radiation Therapy Just as Effective as Conventional Schedule

A boost dose of radiation delivered during an accelerated (hypofractionated) schedule reduced overall treatment time and was just as effective at reducing the risk of early-stage breast cancer coming back (recurrence) as a boost dose delivered after the final treatment of a conventional radiation schedule, according to a study.

The research was presented on Oct. 24, at the 2022 American Society for Radiation Oncology (ASTRO) 2022 Annual Meeting. Read the abstract of “NRG RTOG 1005: A Phase III Trial of Hypo Fractionated Whole Breast Irradiation with Concurrent Boost vs. Conventional Whole Breast Irradiation plus Sequential Boost Following Lumpectomy for High Risk Early-Stage Breast Cancer.”

In many cases, people diagnosed with early-stage breast cancer receive radiation therapy after surgery to remove the cancer. Radiation therapy lowers the risk of recurrence.

A traditional whole-breast radiation therapy schedule involves 25 treatments — one treatment five days a week for five to seven weeks. Radiation oncologists measure the dose of radiation therapy in Gray. People on traditional radiation therapy schedules receive 45 to 50 Gray in a five- to seven-week period — 1.8 to 2 Gray during each treatment.

But a five- to seven-week nearly daily commitment is difficult for many people, especially if they live far away from a treatment center.

So doctors developed a radiation therapy schedule that involves fewer treatments that deliver higher doses of radiation during each treatment. This accelerated schedule allows people to receive about the same radiation dose in a three- to five-week schedule.

Both the National Comprehensive Cancer Network (NCCN) and ASTRO say that an accelerated schedule should be the standard of care for whole-breast radiation therapy. The preferred accelerated schedule is 40 Gray in 15 treatments or 42.5 Gray in 16 treatments. 

A radiation boost is a supplemental dose of radiation targeted directly at the area where the cancer was.

Typically, people on either schedule receive a boost dose after their last radiation treatment. But it adds another week or so to the total treatment time.

One of the goals of an accelerated radiation schedule is to shorten treatment time. So in this study, the researchers wanted to know if delivering a boost dose of radiation to the surgical cavity during each treatment in an accelerated three-week course of whole-breast radiation offered the same reduction in recurrence risk as a traditional five-week course of whole-breast radiation followed by a boost dose.

The study included 2,262 people diagnosed with stage 0, stage I, or stage II breast cancer with a high risk of recurrence.

The cancer had a high risk of recurrence because of various factors:

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  higher tumor grade

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  older age at diagnosis

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  chemotherapy before surgery

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  estrogen receptor-negative status

All the people had lumpectomy to remove the cancer and were scheduled to have radiation.

The researchers randomly split the people into two radiation treatment groups:

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  1,124 people were in the traditional whole-breast radiation group and received 50 Gray in 25 treatments or 42.7 Gray in 16 treatments, plus a boost of 12 Gray in six treatments or 14 Gray in seven treatments after the 25 or 16 treatments

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  1,138 people were in the accelerated whole-breast radiation group and received 40 Gray in 15 treatments, plus a boost of 0.53 Gray in each of the 15 treatments

The researchers followed half the people for more than 7.3 years and the other half for shorter periods of time.

Overall, there were 56 ipsilateral recurrences, meaning the cancer came back in the same breast as the original cancer.

Among the people who received traditional whole-breast radiation therapy followed by a boost:

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  the five-year ipsilateral recurrence rate was 2%

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  the seven-year ipsilateral recurrence rate was 2.2%

Among the people who received accelerated whole-breast radiation therapy as well as a boost during each treatment:

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  the five-year ipsilateral recurrence rate was 1.9%

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  the seven-year ipsilateral recurrence rate was 2.6%

So the recurrence rate was basically the same, no matter when the people received the boost dose.

Overall treatment time was about a week and a half shorter for those in the accelerated group who received the boost during each treatment.

Side effects were similar between the two treatment groups.

“[These] data [are] incredibly important because the current standard of a sequential boost after [hypofractionated whole-breast radiation] or [conventional whole-breast radiation] adds additional treatment time which directly impacts patients’ lives,” lead author Frank A. Vicini, MD, a radiation oncologist with GenesisCare, said in a statement. “By delivering [hypofractionated whole-breast radiation] with a concurrent boost within three weeks we have the ability to deliver a similarly efficacious treatment option, but at a great convenience for our patients and with comparable toxicity outcomes.”

If you’ve been diagnosed with early-stage breast cancer and whole-breast radiation therapy is part of your treatment plan, you may want to talk to your doctor about this study. You can discuss whether an accelerated schedule that includes the boost during each treatment makes sense for you and your unique situation.

Learn more about radiation therapy.