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Breast-conserving therapy vs mastectomy in early-stage breast cancer: a meta-analysis of 10-year survival |
Morris A D, Morris R D, Wilson J F, White J, Steinberg S, Okunieff P, Arriagada R, Le M G, Blichert-Toft M, van Dongen J A |
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Authors' objectives To assess whether 10-year survival in early-stage breast cancer is affected by type of surgery.
Searching MEDLINE was searched from 1966 to 1995 for English language papers only.
Study selection Study designs of evaluations included in the reviewRandomised controlled trials (RCTs), comparing mastectomy with breast-conserving therapy in the treatment of early-stage breast cancer, were included.
Specific interventions included in the reviewMastectomy, breast-conserving therapy (BCT), with or without radiotherapy.
Participants included in the reviewWomen with early (stage I or II) breast cancer were included.
Outcomes assessed in the reviewThe outcome assessed was 10-year survival.
How were decisions on the relevance of primary studies made?The authors do not state how the papers were selected for the review, or how many of the authors performed the selection.
Assessment of study quality The authors do not report the method used to assess validity, or how the validity assessment was performed. One series (2 studies) was rejected because of "inconsistencies and differences in treatment protocol for BCT".
Data extraction Original patient-level data was requested for all studies. When this information was not available, data was identified from the most recent publication. For each study, the number of subjects alive at the beginning of each year after randomisation was estimated, together with the number of patients who died and the number censored during the year. If the relevant numbers were available in tables, they were extracted directly; if not, they were estimated from survival curves by 2 readers who were blind to treatment.
Methods of synthesis How were the studies combined?The survival rates for each year of each treatment arm were determined, along with survival rates for sub-groups according to nodal status and tumour size. Studies were also divided into those where more, or fewer, than 50% of node-positive patients had radiotherapy. The odds of death among patients who underwent BCT, relative to corresponding odds among those who had mastectomy, were calculated for each year of each study. The odds ratios and survival rates were pooled using a random-effects model (DerSimonian and Laird).
How were differences between studies investigated?No further investigation of differences was mentioned.
Results of the review Seven RCTs were identified, of which 6 were included in the meta-analysis (n=3865).
Overall survival was similar for both treatments. Survival rates appear slightly higher among patients treated with BCT but the differences are not significant. The pooled odds ratios were 0.90 (95% CI: 0.74 to 1.09) and 0.91 (95% CI: 0.78 to 1.05) at 5 and 10 years, respectively. When the series which had been rejected was included, differences remained insignificant with a wider confidence interval (95% CI: 0.85 to 1.32). No subgroup had an odds ratio significantly different to 1.
Analysis according to proportion of node-positive women who received radiotherapy showed that when more than 50% of patients in both study arms received radiotherapy, both treatments led to similar survival rates. If fewer than 50% in both study arms received radiotherapy, survival was significantly better after BCT (with routine radiotherapy for all patients); odds ratio 0.69 (95% CI: 0.49 to 0.97; p=0.03).
Authors' conclusions The survival rates with BCT are at least as high as survival rates after mastectomy. Under some conditions, particularly for node-positive patients, BCT may confer a survival advantage.
CRD commentary Despite the fact that the search was limited to MEDLINE and English language papers, it is unlikely that important studies will have been missed. The criteria for rejecting one series appears arbitrary, but inclusion of this data in the analysis does not affect the conclusion.
Implications of the review for practice and research Breast-conserving therapy followed by radiotherapy is at least as effective as mastectomy.
Bibliographic details Morris A D, Morris R D, Wilson J F, White J, Steinberg S, Okunieff P, Arriagada R, Le M G, Blichert-Toft M, van Dongen J A. Breast-conserving therapy vs mastectomy in early-stage breast cancer: a meta-analysis of 10-year survival. Cancer Journal from Scientific American 1997; 3(1): 6-12 Other publications of related interest Early Breast Cancer Trialists' Collaborative Group. Effects of radiotherapy and surgery in early breast cancer. An overview of randomized trials. N Engl J Med 1995;333:1444-55.
Indexing Status Subject indexing assigned by NLM MeSH Breast Neoplasms /mortality /therapy; Combined Modality Therapy; Demography; Female; Humans; Mastectomy /methods; Mastectomy, Segmental; Odds Ratio; Randomized Controlled Trials as Topic; Survival Analysis AccessionNumber 11997000773 Date bibliographic record published 30/11/1998 Date abstract record published 30/11/1998 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
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