Similarly, "disease-free survival" is the length of time after patients have received treatment and have no detectable disease.
Time to progression (TTP) does not count patients who die from other causes but is otherwise a close equivalent to PFS (unless there are many such events).
[4] The definition of "progression" generally involves imaging techniques (plain radiograms, CT scans, MRI, PET scans, ultrasounds) or other aspects: biochemical progression may be defined on the basis of an increase in a tumor marker (such as CA125 for epithelial ovarian cancer or PSA for prostate cancer).
In a time trade off study in renal cancer, physicians rated PFS the most important aspect of treatment, while for patients it fell below fatigue, hand foot syndrome, and other toxicities.
[5] It is a metric frequently used by the UK National Institute for Health and Clinical Excellence[6] and the U.S. Food and Drug Administration to evaluate the effectiveness of a cancer treatment.