Fraction size in radiation therapy for breast conservation in early breast cancer.

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 update of a Cochrane Review first published in 2008 and updated in 2009.

OBJECTIVES: To assess the effect of altered radiation fraction size for women with early breast cancer who have had breast conserving surgery.

SEARCH METHODS: We searched the Cochrane Breast Cancer Specialised Register (23 May 2015), CENTRAL (The Cochrane Library 2015, Issue 4), MEDLINE (Jan 1996 to May 2015), EMBASE (Jan 1980 to May 2015), the WHO International Clinical Trials Registry Platform (ICTRP) search portal (June 2010 to May 2015) and ClinicalTrials.gov (16 April 2015), reference lists of articles and relevant conference proceedings. No language or publication constraints were applied.

SELECTION CRITERIA: Randomised controlled trials of altered fraction size versus conventional fractionation for radiation therapy in women with early breast cancer who had undergone breast conserving surgery.

DATA COLLECTION AND ANALYSIS: Two authors performed data extraction independently, with disagreements resolved by discussion. We sought missing data from trial authors.

MAIN RESULTS: We studied 8228 women in nine studies. Eight out of nine studies were at low or unclear risk of bias. Altered fraction size (delivering radiation therapy in larger amounts each day but over fewer days than with conventional fractionation) did not have a clinically meaningful effect on: local recurrence-free survival (Hazard Ratio (HR) 0.94, 95% CI 0.77 to 1.15, 7095 women, four studies, high-quality evidence), cosmetic outcome (Risk ratio (RR) 0.90, 95% CI 0.81 to 1.01, 2103 women, four studies, high-quality evidence) or overall survival (HR 0.91, 95% CI 0.80 to 1.03, 5685 women, three studies, high-quality evidence). Acute radiation skin toxicity (RR 0.32, 95% CI 0.22 to 0.45, 357 women, two studies) was reduced with altered fraction size. Late radiation subcutaneous toxicity did not differ with altered fraction size (RR 0.93, 95% CI 0.83 to 1.05, 5130 women, four studies, high-quality evidence). Breast cancer-specific survival (HR 0.91, 95% CI 0.78 to 1.06, 5685 women, three studies, high quality evidence) and relapse-free survival (HR 0.93, 95% CI 0.82 to 1.05, 5685 women, three studies, moderate-quality evidence) did not differ with altered fraction size. We found no data for mastectomy rate. Altered fraction size was associated with less patient-reported (P < 0.001) and physician-reported (P = 0.009) fatigue at six months (287 women, one study). We found no difference in the issue of altered fractionation for patient-reported outcomes of: physical well-being (P = 0.46), functional well-being (P = 0.38), emotional well-being (P = 0.58), social well-being (P = 0.32), breast cancer concerns (P = 0.94; 287 women, one study). We found no data with respect to costs.

AUTHORS' CONCLUSIONS: We found that using altered fraction size regimens (greater than 2 Gy per fraction) does not have a clinically meaningful effect on local recurrence, is associated with decreased acute toxicity and does not seem to affect breast appearance, late toxicity or patient-reported quality-of-life measures for selected women treated with breast conserving therapy. These are mostly women with node negative tumours smaller than 3 cm and negative pathological margins.