Some Statistical Issues and Misunderstandings in the Assessment of PFS
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*Kevin J. Carroll, Astra Zeneca Pharmaceuticals 


With the advent of ever more effective second and third line cancer treatments, progression-free survival (PFS) is an increasingly important endpoint in oncologic drug development. However, several statistical concerns exist regarding the use of PFS as a basis to compare treatments. Unlike survival, the exact time of progression is unknown, so progression times might be over-estimated and, consequently, bias may be introduced when comparing treatments. Further, it is not uncommon for randomized therapy to be stopped prior to progression being documented due to toxicity or the initiation of additional anti-cancer therapy; in such cases patients are frequently not followed further for progression and, consequently, are right-censored in the analysis. These issues and others, such as the broader debate around whether PFS is a benefit in and of itself or just a surrogate endpoint for overall survival, will be covered in this talk.