Progression-free survival (PFS) is "the length of time during and after the treatment of a disease, such as cancer, that a patient lives with the disease but it does not get worse". In
oncology
Oncology is a branch of medicine that deals with the study, treatment, diagnosis and prevention of cancer. A medical professional who practices oncology is an ''oncologist''. The name's etymological origin is the Greek word ὄγκος (''ó ...
, PFS usually refers to situations in which a tumor is present, as demonstrated by laboratory testing, radiologic testing, or clinically. 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). The FDA gives separate definitions and prefers PFS.
Background
PFS is widely used as a
surrogate endpoint In clinical trials, a surrogate endpoint (or surrogate marker) is a measure of effect of a specific treatment that may correlate with a ''real'' clinical endpoint but does not necessarily have a guaranteed relationship. The National Institutes of He ...
in oncology.
The definition of "progression" generally involves imaging techniques (plain
radiograms,
CT scans,
MRI
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...
,
PET scan
Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...
s,
ultrasound
Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
s) 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
Surface epithelial-stromal tumors are a class of ovarian neoplasms that may be benign or malignant. Neoplasms in this group are thought to be derived from the ovarian surface epithelium (modified peritoneum) or from ectopic endometrial or Fallo ...
or
PSA
PSA, PsA, Psa, or psa may refer to:
Biology and medicine
* Posterior spinal artery
* Primary systemic amyloidosis, a disease caused by the accumulation of abnormal proteins
* Prostate-specific antigen, an enzyme used as a blood tracer for pros ...
for
prostate cancer
Prostate cancer is cancer of the prostate. Prostate cancer is the second most common cancerous tumor worldwide and is the fifth leading cause of cancer-related mortality among men. The prostate is a gland in the male reproductive system that sur ...
). In clinical trials, what precisely constitutes an "event" in PFS (an event being either disease progression or death) may vary depending on the specific disease and/or the toxicological characteristics of the treatments in the trial; however, this is generally defined in the trial protocol prior to the trial enrolling patients.
, change in the radiological aspects of a lesion is defined according to
RECIST criteria. Progression may also be due to the appearance of a new lesion or to unequivocal progression in other lesions, such as an increase in size or the lesions spreading to nearby tissues.
Progression-free survival is commonly used as an alternative to overall survival (OS). In some cancers, PFS and OS are strictly related, but in others they are not. 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.
Special aspects
By definition, PFS refers to the date on which progression is detected. An advantage of measuring PFS over measuring OS is that PFS appears sooner than deaths, allowing faster trials. PFS also allows for greater insight into consequences of diseases and treatments that fall below the threshold of mortality, such as pain, organ dysfunction, interference in daily life, and other effects that progressive disease may have on the patient while they are still alive.
The use of PFS for proof of effectiveness and regulatory approval is controversial. It is often used as a clinical endpoint
Clinical endpoints or clinical outcomes are Outcome measure, outcome measures referring to occurrence of disease, symptom, Medical sign, sign or laboratory abnormality constituting a target outcome in clinical trial, clinical research trials. The t ...
in randomized controlled trials for cancer therapies. It is a metric frequently used by the UK National Institute for Health and Clinical Excellence
The National Institute for Health and Care Excellence (NICE) is an executive non-departmental public body of the Department of Health and Social Care in England that publishes guidelines in four areas:
* the use of health technologies withi ...
and the U.S. Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
to evaluate the effectiveness of a cancer treatment. Studies find that new cancer drugs approved by the U.S. Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
improve progression-free survival by a median of 2 to 3 months depending on the sample and analyzed time period: 2.5 months, 2.70 months, 3.30 months.
PFS improvements do not always result in corresponding improvements in overall survival, and the control of the disease may come at the biological expense of side effects from the treatment itself. This has been described as an example of the McNamara fallacy
The McNamara fallacy (also known as the quantitative fallacy), named for Robert McNamara, the US Secretary of Defense from 1961 to 1968, involves making a decision based solely on quantitative observations (or metrics) and ignoring all others. ...
.
See also
* Survival rate
Survival rate is a part of survival analysis. It is the proportion of people in a study or treatment group still alive at a given period of time after diagnosis. It is a method of describing prognosis in certain disease conditions, and can be use ...
References
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Medical terminology