Boost Dose After Radiation for Moderate- or High-Grade DCIS Reduces Recurrence Risk
After whole-breast radiation, a boost dose to the area where the tumor was further reduced the risk of moderate- or high-grade DCIS (ductal carcinoma in situ) coming back (recurrence).
The research was published in the Aug. 6, 2022, issue of the journal The Lancet. Read the abstract of “Radiation doses and fractionation schedules in non-low-risk ductal carcinoma in situ in the breast (BIG 3-07/TROG 07.01): a randomised, factorial, multicentre, open-label, phase 3 study.”
DCIS is non-invasive breast cancer that starts in the milk ducts. According to the American Cancer Society, about 20% of new breast cancers are DCIS.
Because all DCIS is stage 0, doctors use the cancer’s grade to decide which treatment options to recommend. DCIS has three grades:
Low-grade or grade I DCIS cells look only a little bit different from healthy breast cells and grow slowly. Low-grade DCIS is less likely to come back than moderate- or high-grade DCIS.
Moderate-grade or grade II (also called intermediate-grade) DCIS cells look more different from healthy breast cells than low-grade DCIS and grow faster. Moderate-grade DCIS is more likely to come back than low-grade DCIS, but less likely to come back than high-grade DCIS.
High-grade or grade III DCIS cells look much different from healthy breast cells and tend to grow more quickly. High-grade DCIS has a higher risk of coming back than low- or moderate-grade DCIS.
Doctors usually treat DCIS with surgery to remove the cancer — lumpectomy in most cases. After surgery, depending on the grade and hormone receptor status of the DCIS, doctors may recommend other treatments, such as radiation or hormonal therapy.
DCIS isn’t life-threatening, but if you’re diagnosed with DCIS, you have a higher-than-average risk of developing invasive breast cancer later in life.
About radiation therapy schedules
Traditionally, a whole-breast radiation therapy schedule involved 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 at 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 with higher doses of radiation at each treatment. This accelerated (also called hypofractionated) 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 the American Society for Radiation Oncology (ASTRO) say that an accelerated schedule should be the standard of care for whole-breast radiation therapy. The preferred hypofractionated dose schedule is 40 Gray in 15 doses or 42.5 Gray in 16 doses.
A radiation boost is a supplemental dose of radiation targeted directly at the area where the cancer was located.
About the study
When this study started in 2007, there wasn’t much research on:
using an accelerated radiation schedule to treat DCIS
whether a radiation boost dose could reduce the risk of recurrence in people diagnosed with DCIS
Known as BIG 3-07/TROG 07.01, this study included 1,608 women from 11 countries who had been diagnosed with moderate- or high-grade DCIS that had been removed with lumpectomy.
The researchers randomly assigned the women to either a traditional or accelerated whole-breast radiation schedule:
831 women were on a traditional schedule
777 women were on an accelerated schedule
The researchers then randomly assigned the women to one of two groups — one that would receive a radiation boost dose and one that would not:
803 women received a boost dose
805 women didn’t receive a boost dose
About 13% of the women in the boost group and 13% of the women in the no boost group also were scheduled to take hormonal therapy medicine.
Follow-up time was 10 years.
After five years of follow-up:
2.9% of the women who received a radiation boost had a recurrence
7.3% of the women who didn’t receive a radiation boost had a recurrence
This difference was statistically significant, which means that it was likely because of the boost dose and not just due to chance.
The radiation schedules the women were on didn’t make a difference in recurrence rates.
Women who received a boost dose had more grade 2 breast pain and skin stiffness than women who didn’t receive a boost dose:
14% of the women who received a boost dose had breast pain versus 10% of the women who didn’t receive a boost dose
14% of the women who received a boost dose had skin stiffness versus 6% of the women who didn’t receive a boost dose
The radiation schedules the women were on didn’t make a difference in the severity of side effects.
“In patients with resected non-low-risk DCIS, a tumour bed boost after [whole-breast radiation] reduced local recurrence with an increase in grade 2 or greater toxicity,” the researches concluded. “The results provide the first randomised trial data to support the use of boost radiation after post-operative [whole-breast radiation] in these patients to improve local control. The international scale of the study supports the generalisability of the results.”
What this means for you
If you’ve been diagnosed with moderate- or high-grade DCIS, you may want to talk to your doctor about the results of this study. You may want to ask if a boost dose makes sense for you if you’re scheduled to receive radiation. At the same time, it’s important to know that the boost dose caused more side effects.
This study did have some weaknesses.
Although most DCIS is hormone receptor-positive, only 13% of the women in each boost group were scheduled to take hormonal therapy, which also reduces the risk of recurrence. It’s also not clear if the women in the study who were prescribed hormonal therapy took it for as long as it was recommended. Both of these factors could have affected recurrence rates.
The researchers also don’t mention any type of genomic testing. Genomic tests analyze a sample of a cancer tumor to see how active certain genes are. The activity level of these genes affects the cancer’s behavior, including how likely it is to grow. Genomic tests are used to help make decisions about whether certain treatments after surgery would be beneficial.
The Oncotype DX Breast DCIS Score genomic test is used:
to help doctors figure out the risk of DCIS coming back (recurrence) and the risk of a new invasive cancer developing in the same breast
how likely a person is to benefit from radiation therapy after DCIS surgery
Results from Oncotype DX Breast DCIS tests could have helped the doctors in the study better decide who would benefit from a radiation boost.
You deserve the best treatment for your unique situation. Your DCIS treatment plan should consider:
your family history of breast cancer and other diseases
your personal health history
any other breast cancer risk factors you may have
the DCIS’s characteristics
any genomic test results
Together, you and your doctor can develop a DCIS treatment plan that makes the most sense for you.
Learn more about Ductal Carcinoma In Situ (DCIS).
Learn more about Radiation Therapy.
Written by: Jamie DePolo, senior editor
— Last updated on August 19, 2022, 2:51 PM