Progression-free survival as a potential surrogate for overall survival in metastatic breast cancer
Catherine Beauchemin,1 Dan Cooper,2 Marie-Ève Lapierre,1 Louise Yelle,3 Jean Lachaine1
1Université de Montréal, Faculté de pharmacie, Montreal, 2Institut national d'excellence en santé et en services sociaux (INESSS), 3Centre Hospitalier de l'Université de Montréal – Hôpital Notre-Dame, Département de médecine, Université de Montréal, Montreal, QC, Canada
Background: Progression-free survival (PFS) and time to progression (TTP) are frequently used to establish the clinical efficacy of anti-cancer drugs. However, the surrogacy of PFS/TTP for overall survival (OS) remains a matter of uncertainty in metastatic breast cancer (mBC). This study assessed the relationship between PFS/TTP and OS in mBC using a trial-based approach.
Methods: We conducted a systematic literature review according to the PICO method: 'Population' consisted of women with mBC; 'Interventions' and 'Comparators' were standard treatments for mBC or best supportive care; 'Outcomes' of interest were median PFS/TTP and OS. We first performed a correlation analysis between median PFS/TTP and OS, and then conducted subgroup analyses to explore possible reasons for heterogeneity. Then, we assessed the relationship between the treatment effect on PFS/TTP and OS. The treatment effect on PFS/TTP and OS was quantified by the absolute difference of median values. We also conducted linear regression analysis to predict the effects of a new anti-cancer drug on OS on the basis of its effects on PFS/TTP.
Results: A total of 5,041 studies were identified, and 144 fulfilled the eligibility criteria. There was a statistically significant relationship between median PFS/TTP and OS across included trials (r=0.428; P<0.01). Correlation coefficient for the treatment effect on PFS/TTP and OS was estimated at 0.427 (P<0.01). The obtained linear regression equation was ΔOS =−0.088 (95% confidence interval [CI] −1.347–1.172) + 1.753 (95% CI 1.307–2.198) × ΔPFS (R2=0.86).
Conclusion: Results of this study indicate a significant association between PFS/TTP and OS in mBC, which may justify the use of PFS/TTP in the approval for commercialization and reimbursement of new anti-cancer drugs in this cancer setting.
Keywords: progression-free survival, time to progression, surrogate endpoint, metastatic breast cancer
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