Relationship between effects on time-to-disease progression and overall survival in studies of metastatic breast cancer

Abstract

The relationship between overall survival (OS) and disease progression end points has been demonstrated in colorectal, colon, and non-small cell lung cancers. We assessed the association between OS and time-to-progression (TTP) or progression-free survival (PFS) in metastatic breast cancer (MBC) studies. A literature search retrieved all randomised controlled trials since 1994 in patients with MBC in which OS and either TTP or PFS were reported. Summary data on trial and patient characteristics were abstracted. Study effect sizes were derived as the ratio of median progression (or survival) times, which approximates the hazard ratio. Effects were centred at zero for regression analyses weighted by sample size. Numerous treatments were represented in 67 studies (17 081 patients). Modeling showed a positive association between outcomes for progression and survival (R 2 ¼ 0.30) with a slope of 0.32 (Po0.001) and a non-significant intercept. Thus, a treatment effect on TTP/PFS translated into a concordant effect on OS, but with attenuated effect size. Similar results were found in models of subsets and sensitivity analyses. These results demonstrate that treatment effects on progression end points in MBC trials are expected to result in treatment differences on OS that are smaller yet consistently in the same direction. British Journal of Cancer (2008) Most studies of anticancer agents are designed and powered to show differences between groups on disease progression end points such as response rates, time-to-progression, time-torecurrence or disease-free survival. Although increased survival time is clearly an implicit goal, it is difficult to establish in randomised studies when standard clinical practise is to change treatments at the onset of new progressive events. Especially in the metastatic setting, where expected survival time may be very short, the use of drug combinations or sequential use of multiple drug classes is commonplace. Increasingly, patients in clinical trials are offered alternate treatment upon progression. Consequently, few studies actually demonstrate an unequivocal survival benefit using intent-to-treat analysis approaches.In several tumour types, efforts have been made to justify the use of alternate, more easily established end points by showing how well they are correlated with survival. Several meta-analyses have been published (Table 1) that show a link between time-toprogression (TTP) or progression-free survival (PFS) with overall survival (OS) in metastatic colorectal or non-small cell lung cancer (Johnson et al, 2006) and colon cancer in the adjuvant setting (Sargent et al, 2005). For breast cancer, a moderately strong correlation between 2-year disease-free survival and 5-year overall survival was observed in the adjuvant setting (Ng et al, 2008). A meta-analysis of metastatic breast cancer studies found a positive relationship between objective response and overall survival on an individual patient basis, but the relationship was less clear when treatment regimens were compared...

Geographic difference in safety and efficacy of systemic chemotherapy for advanced gastric or gastroesophageal carcinoma: a meta-analysis and meta-regression

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