Accuray Incorporated has announced that data from a prospective, phase II trial of 338 women with low-risk breast cancer showed 98.8 percent had local disease control seven years after receiving once-daily accelerated partial breast irradiation (APBI) delivered with the TomoTherapy® System. The study, published online in the International Journal of Radiation Oncology*Biology*Physics, also reported that the once-daily schedule was associated with a very low incidence of acute and late toxicities.
The TomoTherapy platform, including the next-generation Radixact® System, is the first in the world capable of helical radiation delivery. Image-guided, intensity-modulated radiation therapy (IG-IMRT) is continuously delivering from a full 360 degrees around the patient as the treatment table also moves at a deliberate pace, providing greater control of the radiation dose so it conforms precisely to the tumor and helps minimize dose to healthy tissue. This precision enables medical care teams to deliver hypofractionated treatment regimens – a higher dose per fraction in fewer fractions than conventional schedules – such as APBI, with increased confidence.
“Over the last 10 years, breast-conserving surgery and APBI have been widely used in clinical practice for the treatment of low-risk breast cancer. Our large phase 2 trial demonstrated that IG-IMRT delivered using the TomoTherapy System offers improvements over existing techniques and can provide better APBI outcomes in carefully selected patient populations. The system enabled our team to increase the conformality and homogeneity of the dose to the tumor bed and reduce the dose to surrounding healthy tissue, making APBI an effective and convenient option for our patients,” said Prof. Ugo de Paula, Department of Radiation Oncology, San Giovanni-Addolorata Hospital, Rome, Italy.
Enhanced precision enables excellent long-term results: study highlights
Once-daily breast APBI delivered with the TomoTherapy System demonstrated the following:
- Ipsilateral breast tumor recurrence (IBTR) free control was 99.4% at a median follow-up of 76 months. This is important because patients with IBTR may be at high risk for subsequent distant metastasis;
- Locoregional control (no recurrence in ipsilateral breast as well as in regional nodes) was 98.8% at a median follow-up of 76 months;
- Progression-free survival was 98.4% and 92% at 5 and 10 years;
- Treatments were very well tolerated with minimal acute or late side effects. Importantly, there were no cases observed of late toxicity such as pneumonitis or rib fractures;
- More than 95 percent of patients and their physicians rated cosmesis — preservation of the normal appearance of the breast — as good/excellent at two years, the relevant timepoint for evaluation of cosmesis.
“This study builds on existing clinical evidence demonstrating the benefits of the TomoTherapy System in the treatment of breast cancer. Integrated image guidance and helical radiation delivery enables exceptional homogeneity in radiation dose delivery and superior treatments for patients. Dr. de Paula and his colleagues found that even those patients deemed cautionary or unsuitable for APBI by American Society of Radiation Oncology (ASTRO) criteria experienced a low rate of IBTR,” said Fabienne Hirigoyenberry-Lanson, Ph.D., vice president global medical and scientific affairs, at Accuray.
About the Phase II Trial
In this trial, 338 women with low-risk breast cancer received a treatment dose of 3.85 Gray (Gy) delivered by the TomoTherapy® System in 10 consecutive daily fractions, five days per week. Patients who had previously undergone breast-conserving surgery were enrolled in the study. The primary endpoints of this trial were breast tumor recurrence, and acute and late toxicity. Secondary outcomes were progression-free survival (PFS) and rates of adverse cosmesis.