Fraction size in radiation treatment for breast conservation in early breast cancer

Abstract

Background: Shortening the duration of radiation therapy would benefit women with early breast cancer treated with breast conserving surgery. It may also improve access to radiation therapy by improving efficiency in radiation oncology departments globally. This can only happen if the shorter treatment is as effective and safe as conventional radiation therapy. This is an updated version of the original Cochrane Review published in Issue 3, 2008.

Objectives: To determine the effect of altered radiation fraction size on outcomes for women with early breast cancer who have undergone breast conserving surgery.

Search strategy: We searched the Cochrane Breast Cancer Group Specialised Register, MEDLINE, EMBASE and the WHO ICTRP search portal to June 2009, reference lists of articles and relevant conference proceedings. We applied no language constraints.

Selection criteria: Randomised controlled trials of unconventional versus conventional fractionation in women with early breast cancer who had undergone breast conserving surgery.

Data collection and analysis: The authors performed data extraction independently, with disagreements resolved by discussion. We sought missing data from trial authors.

Main results: Four trials reported on 7095 women. The women were highly selected: tumours were node negative and 89.8% were smaller than 3 cm. Where the breast size was known, 87% had small or medium breasts. The studies were of low to medium quality. Unconventional fractionation (delivering radiation therapy in larger amounts each day but over fewer days than with conventional fractionation) did not affect: (1) local recurrence risk ratio (RR) 0.97 (95% CI 0.76 to 1.22, P = 0.78), (2) breast appearance RR 1.17 (95% CI 0.98 to 1.39, P = 0.09), (3) survival at five years RR 0.89 (95% CI 0.77 to 1.04, P = 0.16). Acute skin toxicity was decreased with unconventional fractionation: RR 0.21 (95% CI 0.07 to 0.64, P = 0.007).

Authors' conclusions: Two new studies have been published since the last version of the review, altering our conclusions. We have evidence from four low to medium quality randomised trials that using unconventional fractionation regimens (greater than 2 Gy per fraction) does not affect local recurrence, is associated with decreased acute toxicity and does not seem to affect breast appearance or late toxicity for selected women treated with breast conserving therapy. These are mostly women with node negative tumours smaller than 3 cm and negative pathological margins. Long-term follow up (> 5 years) is available for a small proportion of the patients randomised. Longer follow up is required for a more complete assessment of the effect of altered fractionation.