Large Breasts, Chemotherapy Don’t Seem to Rule Out Hypofractionated Radiation Schedule

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In March 2018, the American Society for Radiation Oncology (ASTRO) released updated guidelines on whole-breast radiation therapy saying that most women diagnosed with breast cancer should be treated with a hypofractionated, or accelerated, radiation schedule.

Still, many breast cancer doctors don’t use a hypofractionated schedule because of concerns about its safety when used with a tumor bed radiation boost or on people who have received chemotherapy or women who have large breasts.

A study suggests that a tumor bed radiation boost, chemotherapy, and/or larger breast size don’t mean that a person shouldn’t be treated with hypofractionated whole-breast radiation after breast cancer surgery.

The research was published online on Oct. 31, 2018, by the Journal of Clinical Oncology. Read the abstract of “Three-Year Outcomes With Hypofractionated Versus Conventionally Fractionated Whole-Breast Irradiation: Results of a Randomized, Noninferiority Clinical Trial.”

Hypofractionated vs. traditional radiation schedule

Women diagnosed with early-stage breast cancer who have lumpectomy to remove the cancer usually have radiation therapy after surgery. Radiation therapy after lumpectomy lowers the risk of the cancer coming back (recurrence) and makes lumpectomy as effective as mastectomy.

Whole-breast radiation therapy after breast cancer surgery is usually given as one treatment per day, 5 days a week, for 5 to 7 weeks. A Gray (Gy) is the way radiation oncologists measure the dose of radiation therapy; if you’re on a 5-week treatment schedule, 50 Gy is the usual amount given during the 5 weeks (2 Gy at each treatment). A supplemental “boost” dose may be included at the end of the regimen that targets the area where the cancer was.

Radiation treatment schedules were developed based on research results. But a 5- to 7-week nearly daily commitment may be difficult for some women, especially if they live far away from a treatment center. So doctors developed and studied different radiation therapy schedules that involve fewer treatments with higher doses of radiation at each treatment, but the same total radiation dose. These hypofractionated radiation schedules put the same radiation dose into a 3- to 5-week schedule.

A hypofractionated whole-breast radiation schedule is appealing to doctors and people getting radiation for several reasons:

  • Convenience: arranging daily trips to get treatment can be a problem for some women, and fewer treatment days or a shorter period of time may be easier to schedule.
  • If radiation is more convenient to schedule, it’s probably easier for women to get all the recommended radiation therapy.

Still, hypofractionated whole-breast radiation use is low in the United States because some doctors have concerns about its safety for a number of reasons:

  • Women with large breasts: the ability to deliver a larger daily dose of radiation requires a radiation treatment plan that is very even throughout the whole breast area. This is sometimes hard to achieve in women with very large breasts.
  • Tumor bed boost: some doctors worry that a boost dose of radiation to the area where the cancer was after a hypofractionated schedule would cause worse cosmetic outcomes or more severe skin side effects.
  • Chemotherapy: doctors also worry that people being treated with chemotherapy, as well as hypofractionated radiation, would have more severe skin side effects.

Women evaluated the outcomes

This study included 286 women diagnosed with stage 0 to stage II breast cancer between 2011 and 2014. All the women had lumpectomy and were scheduled to have radiation therapy after surgery. The women were randomly assigned to one of two radiation schedules:

  • 25 treatments of 2 Gy each for a total of 50 Gy — the traditional schedule (149 women)
  • 16 treatments of 2.66 Gy each for a total of 42.56 Gy — the hypofractionated schedule (137 women)

All the women also received a boost dose of radiation. The boost dose depended on which treatment group the women were in, as well as the size of the surgical margins.

Other characteristics of the women:

  • 28.8% on the traditional schedule and 30.4% on the hypofractionated schedule were treated with chemotherapy
  • 36.9% on the traditional schedule and 37.0% on the hypofractionated schedule had D-EE breast size
  • 90.5% on the traditional schedule and 94.8% on the hypofractionated schedule had an excellent or good cosmetic assessment before radiation treatment

Median follow-up time was 4.1 years. This means that half the women were followed for a longer time and half the women were followed for a shorter time.

Overall, 3 years after radiation treatment ended:

  • 8.2% of the women treated on a hypofractionated schedule
  • 13.6% of women treated on a conventional schedule

reported unfavorable side effects from radiation treatment.

This difference was statistically significant, which means that it was likely due to the difference in treatment and not just because of chance.

Results for specific groups of women were:

  • Chemotherapy: reports of unfavorable side effects were 4.1% higher in the hypofractionated group than the traditional group. Still, this difference was not statistically significant, which means that it could have been due to chance and not because of the difference in treatment.
  • Large breasts: reports of unfavorable side effects were 18.6% lower in the hypofractionated group compared to the traditional group. This different was statically significant, and the researchers said the results suggest a hypofractionated schedule is better for women with larger breasts.

“Three years after whole-breast radiation followed by a tumor bed boost, outcomes with hypofractionation and conventional fractionation are similar,” the researchers wrote. “Tumor bed boost, chemotherapy, and larger breast size do not seem to be strong contraindications to hypofractionated whole-breast radiation. …The findings are also relevant to informing patients, because, to our knowledge, this is the only randomized trial evaluating whole-breast radiation in which the primary outcome is patient reported.”

Still, 3 years of follow-up is relatively short. Also, while there were enough women in the overall study to see if the shorter treatment was effective and had acceptable side effects, the number of women who had chemotherapy and the number of women who had large breasts were relatively small.

It’s important to know that this study does not apply to women with cancer in the lymph nodes or women who require lymph node radiation.

Deciding on a radiation schedule that’s right for you

“If you have early-stage breast cancer, this study shows that a shortened course of radiation is not inferior to conventional treatment, over the first few years of follow-up, for the women in the study as an overall group,” said Breastcancer.org founder and chief medical officer, Marisa Weiss, M.D., a radiation oncologist.

“In hospitals across the country, as patients and doctors work together to figure out the best treatment options, we can now be more open to consider the shorter course in women who've had chemotherapy and who are physically larger — in girth or in breast size,” she continued. “But the power of the study to know if women with very large breasts will have as good a result with the shorter course is limited. Many of my patients have EE-, F-, G-, and J-cup breast size. We also don't know much more regarding women with a large chest circumference — larger than 25 centimeters across the treatment field — regardless of bra cup size. Also, we know little more regarding the safety and effectiveness of the shorter course in women with larger breasts or larger girth who also received chemotherapy.

“Still, with all of these limitations, this study helps patients and doctors share decision-making about the role of short-course radiation for more women than was previously considered. If you choose to follow this newer shorter approach, your doctor will have to make sure that an even dose that's within 8% of the prescribed dose can be achieved in your unique situation, based on your body configuration and the radiation treatment technology available at your therapy center.”

If you’ve been diagnosed with early-stage breast cancer and have had lumpectomy, and radiation therapy is part of your treatment plan, it makes sense to ask your doctor about this study and the ASTRO guidelines and whether hypofractionated whole-breast radiation makes sense for you and your unique situation.

It’s also a good idea to talk to your doctor about skin reactions to radiation — together, you can develop a plan to ease any skin irritation that happens during and after radiation therapy.

For more information, including managing skin side effects, visit the Breastcancer.org Radiation Therapy section.

To talk with others about radiation therapy and its side effects, join the Breastcancer.org Discussion Board forum Radiation Therapy - Before, During, and After.

Written by: Jamie DePolo, senior editor


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