Annals of Oncology Advance Access originally published online on November 20, 2007
Annals of Oncology 2008 19(3):481-486; doi:10.1093/annonc/mdm486
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breast cancer |
Correlation of changes between 2-year disease-free survival and 5-year overall survival in adjuvant breast cancer trials from 1966 to 2006
1 Department of Medical Oncology and Hematology, Princess Margaret Hospital, Faculty of Medicine, University of Toronto, Toronto
2 Biostatistics, Princess Margaret Hospital, Toronto, Canada
* Correspondence to: Dr E. Chen, Department of Medical Oncology and Hematology, Princess Margaret Hospital, Suite 5-719, 610 University Avenue, Toronto, Ontario, Canada M5G 2M9. Tel: +1 416-946-2263; Fax: +1 416-946-4467; E-mail: eric.chen{at}uhn.on.ca
Background: Although disease-free survival (DFS) is accepted as a valid end point in adjuvant breast cancer trials, improvement in 2-year DFS has never been formally established as an adequate correlate for 5-year overall survival (OS). We set out to ascertain if changes in 2-year DFS can be used to accurately predict 5-year OS changes.
Design: We conducted a systematic Medline search (1966–2006) for randomized adjuvant breast cancer trials of >100 patients per arm with 2-year DFS and 5-year OS data. A univariate regression model weighted by trial sample size was constructed to determine whether 2-year DFS differences between treatment arms within trials were predictive of 5-year OS differences.
Results: A total of 126 studies containing 149 treatment comparisons met the inclusion criteria. Difference in 2-year DFS was a significant predictor of difference in 5-year OS. For every 1% increase in 2-year DFS difference, the 5-year OS difference increased by 0.5%–0.55%. The proportion of variation explained ranged from 0.38 to 0.42, with a wide prediction interval.
Conclusion: There is a statistically significant correlation, of moderate strength, between difference in 2-year DFS between treatment comparisons and difference in 5-year OS but the correlation is not strong enough to be used as a predictor.
Key words: breast cancer, correlation, disease-free survival, overall survival
Received for publication July 18, 2007. Revision received September 13, 2007. Accepted for publication September 17, 2007.