IPD from 47 RCTs (n=17,723) were included. These included data on: 17,723 patients in 47 RCTs of polychemotherapy compared with no chemotherapy; 6,104 patients in 11 RCTs of longer polychemotherapy compared with shorter chemotherapy regimens; and 5,942 patients from 11 RCTs of anthracycline-containing polychemotherapy compared with no chemotherapy.
It is unclear from the report why data from ten reports were unavailable, or whether the unavailability of data referred to summary data or specifically to IPD.
For recurrence, polychemotherapy produced substantial and highly significant proportional reductions, both among women aged under 50 years at randomisation (35% reduction; 2p<0.00001) and among those aged 50 to 69 (20% reduction; 2p<0.00001).
For mortality, the reductions were also significant among women aged under 50 years (27% reduction; 2p<0.00001) and among those aged 50 to 69 (11% reduction; 2p=0.0001). The recurrence reductions emerged chiefly during the first 5 years of follow-up, whereas the difference in survival grew throughout the first 10 years.
After standardisation for age and time since randomisation, the proportional reductions in risk were similar for women with node-negative and node-positive disease.
Applying the proportional mortality reduction observed in all women aged under 50 years at randomisation would typically change a 10-year survival of 71% for those with node-negative disease to 78% (an absolute benefit of 7%). The survival would change from 42 to 53% (an absolute benefit of 11%) for those with node-positive disease. The smaller proportional mortality reduction observed in all women aged 50 to 69 years at randomisation would translate into smaller absolute benefits: the 10-year survival would change from 67 to 69% (an absolute gain of 2%) for those with node-negative disease, and from 46 to 49% (an absolute gain of 3%) for those with node-positive disease.
The age-specific benefits of polychemotherapy appeared to be largely irrespective of menopausal status at presentation, oestrogen receptor status of the primary tumour, and of whether adjuvant tamoxifen had been given.
There was a reduction of about one-fifth (2p=0.05) in contralateral breast cancer, which has already been included in the analyses of recurrence.
There was no apparent adverse effect on deaths from causes other than breast cancer (death rate ratio 0.89).
The directly randomised comparisons of longer versus shorter durations of polychemotherapy did not indicate any survival advantage with the use of more than about 3 to 6 months of polychemotherapy.
The directly randomised comparisons did suggest that, compared with CMF alone, the anthracycline-containing regimens produced somewhat greater effects on recurrence (2p=0.006) and mortality (69 versus 72% for 5-year survival; log-rank 2p=0.02). The authors state that (at the time of writing) 'the results of several of the relevant trials are not yet available'.