In the phase III IMPORT HIGH trial reported in The Lancet, Charlotte E. Coles, FRCR, and colleagues found little difference in ipsilateral breast tumor relapse rates with adjuvant dose-escalated simultaneous integrated boost radiotherapy vs lower-dose sequential boost radiotherapy in patients with early-stage breast cancer.
Charlotte E. Coles, FRCR
Study Details
In the open-label multicenter trial, 2,617 women who had breast-conserving surgery for pT1–3p N0–3a M0 invasive carcinoma were randomly assigned 1:1:1 between March 2009 and September 2015 to one of the three following groups:
- 40 Gy/15 fractions to the whole breast and 16 Gy/8 fractions sequential photon boost to the tumor-bed volume (control group; n = 871)
- 36 Gy/15 fractions to the whole breast, 40 Gy/15 fractions to the partial breast, and 48 Gy/15 fractions concomitant photon boost to the tumor-bed volume (test group 1; n = 874)
- 36 Gy/15 fractions to the whole breast, 40 Gy/15 fractions to the partial breast, and 53 Gy/15 fractions concomitant photon boost to the tumor-bed volume (test group 2; n = 872).
The primary endpoint was ipsilateral breast tumor relapse in the intention-to-treat population, with the assumption of a 5-year incidence of 5% in the control group. Noninferiority was predefined as an upper bound of the 95% confidence interval for the absolute difference between control and test groups of ≤ 3%.
Key Findings
At a median follow-up of 74 months, ipsilateral breast tumor relapse events occurred in 20 patients in the control group, 21 in test group 1, and 35 in test group 2.
The incidence of ipsilateral breast tumor relapse at 5 years was 1.9% (95% CI = 1.2%–3.1%) in the control group, 2.0% (95% CI = 1.2%–3.2%) in test group 1, and 3.2% (95% CI = 2.2%–4.7%) in test group 2. The absolute differences in incidence vs the control group were 0.1% (95% CI = –0.8% to 1.7%) for test group 1—satisfying the noninferiority criterion—and 1.4% (95% CI = 0.03%–3.8%) for test group 2.
The 5-year incidence of clinician-reported moderate or marked breast induration was 11.5% in the control group, 10.6% in test group 1 (P = .40 vs control group), and 15.5% in test group 2 (P = .015 vs control group).
The investigators concluded: “In all groups, 5-year ipsilateral breast tumor relapse incidence was lower than the 5% originally expected regardless of boost sequencing. Dose escalation is not advantageous. The 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.”
Charlotte E. Coles, FRCR, of the Department of Oncology, University of Cambridge, is the corresponding author of The Lancet article.
Disclosure: The study was funded by Cancer Research UK. For full disclosures of the study authors, visit thelancet.com.
