Partial-Breast Radiation After BCS Noninferior To Whole-Breast Treatment

After breast conserving surgery for small, non-lobular, invasive carcinoma, treatment with partial-breast or reduced-dose radiation offers a similar relapse risk to whole-breast radiotherapy

medwireNews: UK IMPORT LOW findings demonstrate the noninferiority of partial-breast and reduced-dose radiotherapy regimens to whole-breast radiation for the risk of local relapse in select women who have undergone breast conserving surgery (BCS).

After a median follow-up of 72.2 months, the 5-year estimated cumulative incidence of local relapse was 1.1% for the 674 women who received the standard 40 Gy whole-breast radiotherapy, 0.2% for the 673 women who received 36 Gy whole-breast radiation, and 0.5% for the 669 patients who were given the 40 Gy partial-breast regimen.

There were also similar rates of regional relapse in the groups, affecting one patient each in the 40 Gy and 36 Gy whole-breast treatment arms and two patients who received the partial breast regimen, giving corresponding loco-regional relapse rates of 1%, <1% and 1%. Distant relapse occurred at a rate of 2%, 1% and 2%, respectively.

“Future generations of women diagnosed with breast cancer will benefit not only from the findings of the IMPORT LOW trial itself but also from the advances that will build on its foundational efforts”, writes Reshma Jagsi, from the University of Michigan in Ann Arbor, USA, in a comment published alongside the study in The Lancet.

However, she emphasizes that the findings should “only be generalised to women similar to those actually enrolled: women aged 50 years or older with small, unifocal, non-lobular invasive carcinoma resected with non-cancerous tissue margins of 2 mm or more.”

And as just 2–4% of the patients recruited to the trial arms had positive axillary lymph nodes, the commentator agrees with the study authors who “caution against generalising the results of this trial to node-positive patients.”

At the 5-year assessment, patients who received partial-breast radiation reportedsignificantly fewer cumulative changes in breast appearance than their counterparts who received the standard whole-breast regimen, at 35.1% versus 47.7%, as did those who received reduced dose therapy at 36.7%.

Women were also significantly less likely to report their breast being harder or firmer if they had received the partial-breast or reduced-dose regimen than standard whole-breast radiation, at 15.3% and 21.0% versus 35.3%, and there were fewer reports of moderate or marked skin changes and reduced breast size with partial-breast irradiation, although these differences did not reach statistical significance.

“These findings support our hypothesis that partial-breast radiotherapy using a standard radiation technique can reduce late toxicity without jeopardising local tumour control”, say lead investigator Charlotte Coles, from the University of Cambridge in the UK, and team.

They believe their partial-breast radiotherapy technique using standard medial and lateral tangential beams, which also allows a minimal average heart dose without the need for breath hold, is “safe and effective.”

The authors conclude: “Implementation of this technique will not require additional resources or training in most countries worldwide.”

References

Coles CE, Griffin CL, Kirby AM, et al. Partial-breast radiotherapy after breast conservation surgery for patients with early breast cancer (UK IMPORT LOW trial): 5-year results from a multicentre, randomised, controlled, phase 3, non-inferiority trial. Lancet; Advance online publication 2 August 2017. DOI: http://dx.doi.org/10.1016/S0140-6736(17)31145-5

Jagsi R. Early-stage breast cancer: falling risks and emerging options. Lancet; Advance online publication 2 August 2017. DOI: http://dx.doi.org/10.1016/S0140-6736(17)31599-4

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