I am trying to better understand how are end points in clinical trials defined when Kaplan-Meier method/log rank test is used. I met this problem at first by reading publications and later trying to organise my own research. Here is the problem:
I am analysing 50 patients reciving chemotherapy as first line treatment for lymphoma. Most of them reached remission. I defined their response as complete remission, partial remission, stable disease and progressive dissease.
Estimating overall survival (OS) seems straight-forward. I have time measured from start of treatment (or from intention to treat) until last control/patient's death. Status is noted as 1 if death occured or 0 if patient is still alive or lost to follow up. All patients are analyzed.
I ran into problem when I tried to estimate other endpoints such as PFS (progression free survival), EFS (event free survival), TTP (time to progression), DR (duration of response), DFT (disease free time), TTF (time to treatment failure)... Main questions are - which patients should be taken for analysis and how to measure time passed?
1. For PFS: If patient's disease is progressive although he is being curently treated (resistance to chemotherapy) his status should be noted as 1, but how much time has passed from start of treatment until progression? (zero months?) Should such patients be excluded and only patients with complete/partial remissions analyzed?
2. If I analyse PFS only for patients reaching remission, is their time measured from start of remission (for example after 4 cycles of chematherapy) until death/progression/last control, or from start of treatment?
I hope you can give me your observations and help me overcome these problems. Thank you
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