Adjuvant APBI Not Inferior to Whole-Breast Irradiation in Low-Risk Breast Cancer

Phase III trial results support the use of accelerated partial breast irradiation using multicatheter brachytherapy in low-risk breast cancer patients

medwireNews: Accelerated partial breast irradiation (APBI) with multicatheter brachytherapy is equivalent to whole-breast irradiation with respect to disease control and survival in women with low-risk early breast cancer, suggest phase III trial findings.

The primary as-treated analysis of this randomised trial included 633 patients with stage 0, I or IIA breast cancer who received adjuvant APBI using multicatheter interstitial brachytherapy after breast-conserving surgery while their 551 counterparts were treated with adjuvant whole-breast irradiation with tumour-bed boost.

At 5-year follow-up, ipsilateral local recurrence occurred in nine patients in the APBI treatment arm while five local recurrences were recorded in the control arm, giving cumulative incidence rates at 5 years of 1.44% and 0.92%, respectively.

As the difference between groups was within the prespecified relevance margin of three percentage points, “non-inferiority with respect to the 5-year rate of local recurrence has been confirmed”, says the team led by Vratislav Strnad, from University Hospital Erlangen in Germany, in The Lancet.

Moreover, disease-free and overall survival rates at 5 years were comparable between APBI-treated women and those who received whole-breast irradiation, at 95.03% versus 94.45% and 97.27% versus 95.55%, respectively.

Patients in the APBI group had a 5-year risk of developing late grade 2 or 3 skin and subcutaneous tissue toxicity of 3.2% and 7.6%, respectively, with corresponding rates of 5.7% and 6.3% for those given whole-breast irradiation. Women in the latter group also had a 0.2% risk of grade 3 fibrosis at 5 years while the risk for APBI-treated patients was 0.0%.

The researchers believe that their positive findings will “at least partly change clinical practice” despite the scarcity of multicatheter APBI expertise in some countries, and that “more radiation oncologists will consider interstitial brachytherapy as a valid option for the treatment of breast cancer patients.”

Although the authors of an accompanying commentary commend Vratislav Strnad et al on their “carefully designed and conducted trial”, they do not think that the results “herald the death knell for whole-breast irradiation”.

The trial presents maturing data, they say, with further evidence awaited from other phase III trials of APBI. The commentators also point out that “possible attractions of APBI, such as short overall treatment time and decreased heart dose, are now reflected with modern whole-breast irradiation.”

However, Charlotte Coles, from Cambridge University NHS Foundation Trust in the UK, and John Yarnold, from the Institute of Cancer Research and Royal Marsden Hospital NHS Foundation Trust in London, UK, add: “We know that breast cancer represents a spectrum of different diseases, with variation in prognosis, and that radiotherapy is no longer a one-size-fits-all strategy but ranges from highly complex treatments to the breast and regional lymph nodes, to complete avoidance of any radiation.

“It is likely that APBI will have a place within this array of treatments.”

References

Strnad V, Ott OJ, Hildebrandt G, et al. 5-year results of accelerated partial breast irradiation using sole interstitial multicatheter brachytherapy versus whole-breast irradiation with boost after breast-conserving surgery for low-risk invasive and in-situ carcinoma of the female breast: a randomised, phase 3, non-inferiority trial.Lancet 2015; Advance online publication 19 October. doi: dx.doi.org/10.1016/S0140-6736(15)00471-7

Coles CE, Yarnold JR. Accelerated partial breast irradiation: the new standard? Lancet 2015; Advance online publication 19 October. doi: dx.doi.org/10.1016/S0140-6736(15)00518-8

medwireNews (www.medwireNews.com) is an independent medical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2015