Adjuvant Chemotherapy for Early Breast Cancer
Authors: Bent Ejlertsen
Journal: New England Journal of Medicine (1981)

With long-term follow-up, the DBCG 77B trial demonstrates that oral single-agent cyclophosphamide significantly reduces the risk of recurrence and mortality as compared with no systemic therapy in pre-menopausal patients with high-risk early breast cancer. DBCG 77B is the only randomised trial assessing single-agent cyclophosphamide; and a second comparison suggests that its benefits are comparable to what may be achieved by classic CMF. The lack of benefits from adding methotrexate and fluorouracil to cyclophosphamide paved the way for combining cyclophosphamide with anthracyclines and later taxanes. DBCG 89D showed an incremental benefit in DFS and OS from substituting methotrexate with epirubicin. The advantage of anthracycline-containing three-drug combinations over CMF was confirmed by others and in the individual-patient EBCTCG meta-analysis, while standard AC or EC for four cycles not was superior to classic CMF. A further reduction in breast cancer mortality appeared in the EBCTCG meta-analysis from the addition of a taxane to a standard AC, while the substitution of cycles or drugs with a taxane was not associated with a reduction in mortality. No apparent benefit was observed in an early analysis of the DBCG 82C evaluating the addition of CMF to tamoxifen in post-menopausal high-risk breast cancer patients. Apart from menopausal status, the two trials had identical selection criteria, and the differences in outcome warranted a long-term follow-up of the 82C trial. After ten years of follow-up, CMF in the DBCG 82C was associated with a significant improvement in DFS; but even with 24 years of follow-up, mortality was not significantly improved. The diversity in outcome from the 77C and the 82B trials triggered further studies. The 77B trial used classic CMF with oral cyclophospamide, while a four-weekly intravenous CMF regimen was used in the 82B and C trials, and a three-weekly CMF regimen was used in the succeeding 89B and D trials. The outcome following these CMF regimens has not been compared within the context of a randomised trial. Shifting from the 77B's classic CMF regimen to the 82B four-weekly IV regimen or the 89B three-weekly IV regimen was associated with a 30% increased risk of a DFS event in a multivariate analysis of a population-based cohort study. Furthermore, the four-weekly regimen used in 82B was associated with a 40% increase in mortality. The strengths of the design include identical selection criteria, uniform and prospective registration of treatment, tumour and patient characteristics. Caution is still required due to the non-experimental design of the comparison. Another finding was a substantial difference in the risk of amenorrhoea; and while 15% of patients aged 40 or younger in 77B had regular menses throughout chemotherapy, the corresponding percentage was 37 in 82B and 47 in 89B. The DBCG in collaboration with a Swedish and a Dutch centre participating in the DBCG trial 89B compared CMF with ovarian ablation in premenopausal high-risk breast cancer patients with ER-positive tumours. No significant differences were found in DFS or OS in the preplanned analysis, suggesting that the benefits of CMF may, at least in part, be explained by ovarian suppression in premenopausal patients with ER-positive tumours. However, these results are not clinically useful by themselves as other chemotherapy regimens have been more efficacious, and knowledge is still lacking regarding the benefits from adding ovarian suppression to chemotherapy plus tamoxifen. The results from the DBCG 77B and 82C are in accordance with other large adjuvant trials and the EBCTCG meta-analyses. The benefits obtained with any individual anticancer drug are largely determined by the cancer (somatic) genome; and by being a molecular target of anthracyclines, TOP2A aberrations could obviously be associated with cancer drug benefits. In the DBCG 89D, a significant heterogeneity was observed between a beneficial effect on DFS and OS of epirubicin and the presence of TOP2A, but not the presence of HER2 aberrations. The results obtained in the 89D trial regarding TOP2A have been reproduced by others, but not consistently. However, a recent individual-patient pooled analysis of five adjuvant trials demonstrated that patients with either TOP2A or centromere 17 aberrations, but not with HER2 amplification, benefit from anthracycline-containing adjuvant chemotherapy. Anthracyclins have additional distinct biological mechanisms; and results from the DBCG 89D suggested that tumours with normal TOP2A were only non-responsive to anthracyclines if they were TIMP1 immunoreactive. The DBCG READ trial (N = 2,015) prospectively included patients without TOP2A-aberrated breast cancers, and its results are awaited for prospective confirmation of the results from the DBCG 89D and the individual-patient pooled analysis. Adjuvant chemotherapy substantially reduces the risk of recurrence and mortality of breast cancer, but is also associated with significant toxicity. However, according to a large cohort study from DBCG, chemotherapy can safely be withheld in one fourth of postmenopausal patients who will be without excess mortality following sufficient adjuvant endocrine therapy for ER positive breast cancer. A prognostic standard mortality rate index (PSI) was constructed using regression coefficients obtained in a multivariate fractional polynomials model, and most accurately identified those who could be spared chemotherapy. In addition to age, tumour size, nodal status, histological type and malignancy grade, the PSI also includes ER level addressed as a continuous variable in the MFP model. In the MFP model, absence of LVI was sufficient to counteract the impact of other risk factors, while that could not be achieved with a categorical multivariate model in a prior study. An evaluation of whether the addition of results from a molecular assay may improve the clinical utility of the PSI is on-going, but when used alone evidence from such assays has been insufficient.