As reported in The Lancet Oncology by Kirby et al, 10-year follow-up of the phase III UK IMPORT LOW trial has shown that partial-breast and reduced-dose radiotherapy continue to be associated with similar ipsilateral breast tumor recurrence (IBTR) outcomes compared with whole-breast radiotherapy after breast-conserving surgery in patients with low-risk early-stage breast cancer.
Results at 5 years showed noninferiority of partial-breast and reduced-dose therapy vs whole-breast radiotherapy in IBTR.
Study Details
In the open-label multicenter trial, 2,018 patients were randomly assigned 1:1:1 between May 2007 and October 2010 to receive 40 Gy in 15 fractions to the whole breast (whole-breast group, n = 675), 36 Gy in 15 fractions to the whole breast plus 40 Gy in 15 fractions to the partial breast (reduced-dose group, n = 674), or 40 Gy in 15 fractions to the partial breast (partial-breast group, n = 669). Patients had not received any neoadjuvant or concurrent adjuvant chemotherapy. The primary endpoint of the trial was IBTR.
Key Findings
Median follow-up was between 120 and 121 months among the three groups.
At 10 years, IBTR events had occurred in 17 patients in the whole-breast group, 11 in the reduced-dose group, and 17 in the partial-breast group, with respective cumulative incidence rates of 2.8% (95% confidence interval [CI] = 1.8%–4.5%), 1.9% (95% CI = 1.1%–3.5%), and 3.0% (95% CI = 1.9%–4.8%).
The estimated absolute differences in 10-year IBTR incidence vs the whole-breast group were –1.02% (95% CI = –1.98% to 0.99%) for the reduced-dose group and 0.16% (95% CI = –1.28% to 2.89%) for the partial-breast group.
Low frequencies of moderate or marked adverse effects in breast tissue, ribcage, and lung were observed across all groups. The most common was breast shrinkage, occurring in 9% of the whole-breast group, 9% of the reduced-dose group, and 7% of the partial-breast group.
The investigators concluded: “Long-term follow-up provides further evidence that partial-breast and reduced-dose radiotherapy are as safe and effective as whole-breast radiotherapy in patients with low-risk early breast cancer. These results reaffirm the use of partial-breast radiotherapy delivered with intensity-modulated radiotherapy in this population as standard of care.”
Anna M. Kirby, FRCR, of the Breast Unit, Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Sutton, is the corresponding author for The Lancet Oncology article.
Disclosure: The study was funded by Cancer Research UK. For full disclosures of all study authors, visit The Lancet Oncology.
