The findings from a phase 3 clinical trial are a boon to patient convenience.
“These findings are indeed practice changing. This was a well-designed trial that looked at shortening treatment from 6 weeks down to 3 weeks. And, they showed equivalent local control and importantly, a good cosmetic outcome over time,” said Kathleen Horst, MD, who served as a discussant at a press conference held at the annual meeting of the American Society for Radiation Oncology where the findings were presented.
“This is substantially more convenient. It is cost effective, both for the health care system and for individual patients. Importantly, our patients come in for treatment every day. They’re taking time off of work, they have to arrange for childcare, and they have to arrange for transportation. So this makes a big difference for these patients,” said Dr. Horst, who is a professor of radiation oncology at Stanford (Calif.) Medicine and director of well-being in the radiation department at Stanford Medicine.
The study was presented by Frank A. Vicini, MD, FASTRO, a radiation oncologist with GenesisCare, Farmington Hills, Mich.
“One of the things I think that was surprising is I think all of us were thinking that this might be a more toxic regimen, but as Dr. Vincini showed, over time it was equally effective and with minimal toxicity, and cosmesis over time was stable, and that’s important. Importantly, that included patient-reported outcomes, not just the physician-reported outcomes. Broadly, I think these findings are applicable for many patients, all patients who are receiving whole breast radiotherapy with an added boost. I think over time this is going to improve the quality of life of our patients. It is an innovative change that everyone is going to be excited to embrace,” Dr. Horst said.
Previous randomized, controlled trials showed that an additional radiation dose to the tumor bed following lumpectomy and whole breast irradiation reduces the relative risk of local recurrence by about 35%. However, this increases treatment time for patients who have already endured an extensive regimen. For whole breast irradiation, hypofractionated radiation is in 15-16 fractions over 3 weeks has comparable recurrence rates as a 5-week regimen, but the relevant trials did not examine the effect hypofractionation may have on a radiation boost to the tumor bed of high-risk patients. Because of this lack of evidence, current practice is for the boost to remain sequential in five to eight fractions after completion of whole breast irradiation, which adds a week to a week and a half to treatment length.
The study included 2,262 patients who were randomized to receive a sequential boost or a concomitant boost. After a median follow-up of 7.4 years, there were 54 ipsilateral breast recurrence (IBR) events. The estimated 7-year risk of IBR was 2.2% in the sequential boost and 2.6% in the concurrent risk group (hazard ratio, 1.32; noninferiority test P = .039). Approximately 60% of patients received adjuvant chemotherapy.
Grade 3 or higher adverse events were similar, with a frequency of 3.3% in the sequential group and 3.5% in the concurrent group (P = .79). The researchers used the Global Cosmetic Score to assess outcomes from the perspective of both physicians and patients; 86% of physicians rated the outcome as excellent/good in the sequential group versus 82% in the concurrent group (P = .33).
“For high-risk early-stage breast cancer patients undergoing breast conservation, a concurrent boost with hypofractionated whole breast irradiation as compared to a sequential boost, results in noninferior local recurrence rates with no significant difference in toxicity, noninferior patient-rated cosmesis, no significant difference in physician rated cosmesis, and delivering the entire treatment even at high risk patients in 3 weeks. Just as critical, the use of target volume–based radiation planning for 3-D [three-dimensional] conformal or [intensity-modulated radiation therapy] whole breast irradiation assessed by dose volume analysis is feasible, and resulted in very low toxicity in the treatment arms, regardless of the fractionation schedule, or the boost delivery,” said Dr. Vincini during the press conference.
The study was grant funded. Neither Dr. Vincini nor Dr. Horst had relevant financial disclosures.