Challenges for breast radiotherapy with SIB: the IMPORT HIGH trial
Authors: Jose Luis Guinot, Cristina Gutierrez, Jean Michel Hannoun-Levi
Journal: The Lancet (2024)

The excellent results of the IMPORT HIGH trial,1Coles CE Haviland JS Kirby AM et al.Dose-escalated simultaneous integrated boost radiotherapy in early breast cancer (IMPORT HIGH): a multicentre, phase 3, non-inferiority, open-label, randomised controlled trial.Lancet. 2023; 401: 2124-2137Summary Full Text Full Text PDF PubMed Google Scholar published with more than 6 years of median follow-up, suggest that this treatment is adequate for all patients with breast cancer. In the boost versus no boost trial, the risk of relapse at 5 years of follow-up with 66 Gy to the tumour bed was around 3%, which increased to 6·2% at 10 years. But in young patients (aged 41–50 years) the risk of relapse reached 8·7% at 10 years,2Bartelink H Horiot J-C Poortmans PM et al.Impact of a higher radiation dose on local control and survival in breast-conserving therapy of early breast cancer: 10-year results of the randomized boost versus no boost EORTC 22881–10882 trial.J Clin Oncol. 2007; 25: 3259-3265Crossref PubMed Scopus (884) Google Scholar and for those younger than 41 years it was 13·5% at 10 years. These statistics rose to 13·5% and 24·4% at 20 years, respectively.3Bartelink H Maingon P Poortmans P et al.Whole-breast irradiation with or without a boost for patients treated with breast-conserving surgery for early breast cancer: 20-year follow-up of a randomised phase 3 trial.Lancet Oncol. 2015; 16: 47-56Summary Full Text Full Text PDF PubMed Scopus (502) Google Scholar In the IMPORT HIGH trial, the median age of the group receiving the 48 Gy simultaneous integrated boost (SIB) was 48·9 years. Young age is as important a factor for relapse as the boost dose, so it is essential to know the relapse statistics by age group before assuring that 48 Gy (equivalent to 60 Gy) is sufficient for young patients.4Polo A Polgár C Hannoun-Levi J-M et al.Risk factors and state-of-the-art indications for boost irradiation in invasive breast carcinoma.Brachytherapy. 2017; 16: 552-564Summary Full Text Full Text PDF PubMed Scopus (29) Google Scholar The dose for patients younger than 50 years should be at least equivalent to 66 Gy, as shown in the European Organisation for Research and Treatment of Cancer study, especially if ductal carcinoma in situ is associated.5Vrieling C van Werkhoven E Maingon P et al.Prognostic factors for local control in breast cancer after long-term follow-up in the EORTC boost vs no boost trial: a randomized clinical trial.JAMA Oncol. 2017; 3: 42-48Crossref PubMed Scopus (120) Google Scholar Similarly, many of these patients older than 50 years do not require a boost because they can be treated in 5 days, or even with partial breast irradiation. This scheme is already used in many centres with success, but an analysis by age subgroups is mandatory and will help to make the most appropriate decision of dose to the tumour bed to reduce breast relapses in the long term. JLG reports payment or honoraria from Elekta and payment for expert testimony, support for attending meetings and travel for the 2022 and 2024 ESTRO meetings, and participation on a data safety monitoring board or advisory board from BARD-BD. CG reports payment or honoraria from Elekta and Rubio, and support for attending meetings and travel from Elekta for the 2022 and 2023 ESTRO meetings. JMH-L reports support for attending meetings and travel from Bebig for the 2022 and 2023 ASTRO and ESTRO meetings and participation on a data safety monitoring board or advisory board for Bayer and Elekta. Dose-escalated simultaneous integrated boost radiotherapy in early breast cancer (IMPORT HIGH): a multicentre, phase 3, non-inferiority, open-label, randomised controlled trialIn all groups 5-year IBTR incidence was lower than the 5% originally expected regardless of boost sequencing. Dose-escalation is not advantageous. 5-year moderate or marked adverse event rates were low using small boost volumes. Simultaneous integrated boost in IMPORT HIGH was safe and reduced patient visits. Full-Text PDF Open AccessChallenges for breast radiotherapy with SIB: the IMPORT HIGH trial – Authors' replyWe thank the authors for their positive comments regarding the IMPORT HIGH trial.1 The main points raised are addressed as follows. Full-Text PDF