Eighteen trials (n=9,388) were included in the review. Follow-up ranged from three to 25 years. Randomisation was judged to be adequate in nine studies. Allocation concealment was reported clearly in eight studies. Withdrawals and losses to follow-up were described in 16 studies. No blinding was used in any of the studies.
There were no statistically significant differences observed between breast conservation therapy and mastectomy for overall survival at three years (nine studies), five years (12 studies), 10 years (eight studies), 15 years (six studies) and 20 years (five studies). There was some moderate heterogeneity reported across the studies for overall survival at 15 years (I2=37.7%) and 20 years (I2=59.4%).
There was a statistically significant increase in local regional recurrence of breast cancer with breast conservation therapy at 10 years follow-up compared to treatment with mastectomy (OR 1.55, 95% CI 1.05 to 2.30, eight studies). There was significant statistical heterogeneity across the studies for this outcome (I2=72.9, p=0.00001). There were no significant differences observed between the treatment groups at three years (five studies), five years (10 studies), 15 years (two studies) and 20 years (four studies). There was statistically significant heterogeneity across the trials for local recurrence at five years (I2=55.4%) and 15 years (I2=78.7%) follow-up post treatment. Moderate heterogeneity was observed at three years follow-up (I2=51.1%).
Sensitivity analyses showed no differences between treatment groups when trials in which patients in the breast conservation therapy groups did not accept radiation therapy were excluded.
Subgroup analyses found no differences between breast conservation therapy and mastectomy treatment in overall survival at all follow-up points and local regional recurrence at three, five, 10 and 20 years for patients with tumours up to 5cm diameter. For patients with tumours up to 2cm in diameter, local recurrence was significantly higher for the group receiving breast conservation therapy at the 20 year follow-up period. There were no differences in overall survival or local recurrence at all the remaining follow-up points.