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New data at ESTRO reinforce alternative to whole breast irradiation for early stage breast cancer patients

Clinical equivalence of partial breast irradiation (PBI) and whole breast irradiation (WBI) has been demonstrated in two key phase III randomized trials: the Groupe Européen de Curiethérapie European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) trial administering PBI in five days with multicatheter interstitial brachytherapy (published in the Lancet), and the IMPORT-Low trial administering PBI in three weeks with IMRT (presented at the 10th European Breast Cancer Conference).

Additional results from the GEC-ESTRO trial (abstract #OC-0481), a multicenter phase III study comparing APBI with interstitial multicatheter brachytherapy to WBI were presented by Prof. Csaba Polgár MD, PhD, MSc, Professor and Head of the Radiotherapy Center at the National Institute of Oncology in Budapest, Hungary and co-lead study author, at ESTRO.

The primary objective of the GEC-ESTRO trial was to assess the role of APBI brachytherapy alone compared to WBI with boost in a defined group of patients with invasive (stage I-IIA) breast cancer or ductal carcinoma in situ (DCIS; stage 0) who underwent breast-conserving surgery. Researchers evaluated a total of 1,184 patients aged 40 years and above who were randomized to a standardized treatment arm (WBI, n=551) or an investigational treatment arm (APBI, n=633). The median follow up in the study was 6.6 years.

“My colleagues and I are pleased to share the data from the GEC-ESTRO trial which further validate the established and growing body of clinical evidence supporting APBI with multicatheter interstitial brachytherapy as a safe and effective alternative to WBI,” says Prof. Polgár. “The convenience of this five-day treatment coupled with excellent cosmetic outcomes make this a very attractive treatment option for women with early breast cancer.”

Previous findings from the multicenter study conducted by GEC-ESTRO, already published in the Lancet, demonstrate that APBI with multicatheter interstitial brachytherapy has an equivalent rate of overall survival, disease-free survival and local and regional cancer control as compared to traditional WBI with boost after breast conserving surgery for selected patients with stage 0-II breast cancer. At five-year follow-up, cumulative recurrence rates for WBI and APBI were 1.44% and 0.92% (p=0.42) respectively. Five-year overall survival was 95.55% with WBI versus 97.27% for APBI and a low incidence of all serious late side effects (around 3% in both arms) was noted.

The new data presented provide additional insights into the late side effect and cosmetic results. Among the 1,184 original study patients, five-year follow-up records on late toxicities and cosmetic results were available for 969 patients (82%). The five-year toxicity profile was similar for patients treated with breast conserving surgery followed by either APBI using interstitial multicatheter brachytherapy or conventional WBI with tumor bed boost. However, a trend towards fewer late skin side effects and better cosmetic results was observed in the APBI arm.

There were no grade 4 toxicities reported. The cumulative incidence of grade 2-3 late skin toxicity at five years was 5.7% with WBI vs 3.2% with APBI (p=0.08). The cumulative risk of grade 2-3 late subcutaneous tissue effects at 5 years was 6.3% with WBI vs 7.6% with APBI (p=0.53). The cumulative incidence of severe (grade 3) fibrosis at five years was 0.2% with WBI and 0% with APBI (p=0.46). The cumulative incidence of grade 2-3 breast pain was low in both the WBI and APBI arms (3.2% vs 1.4%;p=0.04). The rate of excellent/good cosmetic results judged by patients was 87.2% with WBI vs 90.4% with APBI ,and 86.7% with WBI vs 88.2% with APBI (p=0.07) when scored by physicians. However, significantly more patients (43.6% vs 30.9%; p=00002) experienced excellent cosmetic results after APBI.

“APBI with interstitial multicatheter brachytherapy offers a significantly shorter treatment course with equivalent local tumor control, less late skin side effects, and better cosmetic results compared to conventional WBI,” concludes Prof. Polgár.

“Early stage breast cancer has high unmet medical needs and places an enormous physical, emotional and economic burden on women, families and health care systems,” notes Prof. Vratislav Strnad, MD, PhD, chair of the GEC-ESTRO Breast Cancer Working Group and radiation oncologist at the Department of Radiation Oncology of University Hospital in Erlangen, Germany. “We anticipate these data will drive significant changes in how clinicians approach early stage breast cancer treatment in patients 50 years and older and place APBI multicatheter brachytherapy as an accepted standard alternative to whole breast irradiation.”

About APBI with Brachytherapy

Accelerated partial breast irradiation with brachytherapy (APBI brachytherapy) is a shortened course of high-dose radiation therapy for early-stage breast cancer patients where radiation is delivered directly into the tumor bed. APBI brachytherapy is delivered as part of breast conservation therapy (BCT), which consists of lumpectomy surgery followed by radiation.

The traditional approach for radiation therapy as part of BCT has been whole breast irradiation (WBI). A full course of WBI exposes the entire breast and surrounding critical structures to radiation and requires daily treatments for three to seven weeks where radiation is delivered from outside the breast. APBI brachytherapy delivers radiation only to the lumpectomy cavity and immediate surrounding tissue. APBI brachytherapy offers three significant advantages over WBI: a reduction in total radiation exposure, particularly to the heart, lungs and skin, a reduced treatment time and the preservation of future organ sparing treatment options.