Breast-Conserving Surgery APBI Regimen ‘Valid Alternative’ To Whole-Breast Irradiation

Toxicity and cosmetic outcomes for accelerated partial breast irradiation plus interstitial brachytherapy after breast-conserving surgery are not inferior to whole-breast radiotherapy

medwireNews: Phase III trial findings add support for the use of accelerated partial breast irradiation (APBI) plus interstitial brachytherapy (IB) after breast-conserving surgery, on finding a reduced risk of the development of grade 2 and 3 skin side effects compared with conventional whole-breast irradiation.

The 5-year results of the GEC-ESTRO trial of women with stage 0–IIA disease, all of whom had achieved a microscopically clear margin of 2 mm, showed that this benefit was achieved without impairing the cosmetic effect or increasing the rate of other adverse events, report Csaba Polgár, from the National Institute of Oncology in Budapest, Hungary, and co-investigators.

The trial’s primary endpoint of ipsilateral local recurrence was previously reported as equivalent between the treatments here.

“On the basis of our findings, APBI with interstitial brachytherapy can be regarded as a valid alternative treatment option after breast-conserving surgery, and can be offered for all patients with low-risk breast cancer as part of routine clinical practice”, the team writes in The Lancet Oncology.

Participants from 16 centres in seven European countries were randomly assigned to receive 50 Gy of whole-breast irradiation plus a 10 Gy tumour-bed boost over approximately 6 weeks (n=673) or 30–32 Gy of APBI given in seven or eight fractions plus 50 Gy given via pulsed-dose brachytherapy, with treatment lasting 4–5 days (n=655).

After a median of 6.6 years, there were no grade 4 toxicities and grade 3 late skin toxicity was recorded in less than 1% of 484 patients treated with APBI and 2% of 393 patients given whole-breast irradiation. Grade 3 late subcutaneous tissue toxicity was absent in the APBI group and occurred in less than 1% of the whole-breast irradiation group.

Grade 2 or more severe late side effects occurred in a comparable 23.3% of the APBI and 27.0% of the whole-breast irradiation groups at 5 years, but the cumulative 5-year incidence of grade 2–3 late skin toxicity was lower in the APBI-treated patients, at 6.9% versus 10.7%, with a significant 3.8% difference.

There was no significant difference in the 5-year cumulative risk of grade 2–3 late subcutaneous tissue adverse events between the APBI and whole-breast irradiation treatment groups (12.0 vs 9.7%)or the cumulative incidence of grade 2–3 breast pain (8.4 vs 11.9%).

Patients in the APBI and whole-breast irradiation groups had similar views on their cosmetic outcomes, with 92% and 91% reporting an excellent to good result during follow-up, and this was in agreement with physician reports, at 93% and 90%, respectively.

Three breast cancer deaths occurred in each treatment group and there were no treatment-related mortalities.

Charlotte Coles, from Addenbrookes’s Hospital Oncology Centre in Cambridge, UK, commends the trial investigators for “meticulous assessment and reporting of late toxicity” and “robust” follow-up in an accompanying comment.

“Whether or not this brachytherapy APBI technique becomes widely adopted remains to be seen, because of limitations in expertise and higher cost than hypofractionated external beam radiotherapy”, she writes.

“We need mature results of other randomised controlled trials, but this GEC-ESTRO trial is a valuable piece in the emerging jigsaw picture of APBI”, the commentator continues, adding that “it emphasises the importance of high-quality late toxicity data from breast radiotherapy trials, since these survivorship issues are vital in an era of excellent local control and survival.”

References

Polgár C, Ott OJ, Hildebrandt G, et al. Late side-effects and cosmetic results of accelerated partial breast irradiation with interstitial brachytherapy versus whole-breast irradiation after breast-conserving surgery for low-risk invasive and in-situ carcinoma of the female breast: 5-year results of a randomised, controlled, phase 3 trial. Lancet Oncol; Advance online publication 13 January 2017. DOI: http://dx.doi.org/10.1016/S1470-2045(17)30011-6

Coles CE. Another piece in the jigsaw of accelerated partial breast irradiation. Lancet Oncol; Advance online publication 13 January 2017. DOI: http://dx.doi.org/10.1016/S1470-2045(17)30001-3

medwireNews (www.medwireNews.com) is an independent medical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2017