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What is “Stable Disease’ in Cancer terminology

March 24, 2013

A discussion on ‘Stable disease or ‘disease free state’

Oncology nomenclature seeks to describe different disease states in and around one of the most sensitive and difficult areas of medicine. It is difficult because, despite some staggering progress in patient outcomes in recent years, oncology remains one of the hardest areas to show real progress.  The reason for the difficulty in using recognisable terms is because cancer is not one disease but a multitude of disease factors all wrapped up in the term ‘cancer’.  The widest dictionary definition of the word cancer is, growth. It is estimated that the physiological processes that combine to create the conditions for tissue to ‘grow’ in an unchecked manner, may number over 200.

When this is placed into context, one can see why cancer is such a difficult physical anomaly to treat. It is amazingly complex and we are still scratching the surface in terms of our understanding of what cancer actually is and how we can treat it.

The unpalatable (for some) truth is that we do not yet know how to cure cancer. The notion of a cure invokes such emotional responses from interested parties, which include patients, friends, and patient groups to name a few. However, the scientific community remains steadfast in its desire to create treatment options that will make a significant difference to patient’ outcomes.

Here is the truth on the global effort to treat cancers. The scientific community’s realistic goal is to, in the short to medium term, turn cancer from an acute disease to a chronic disease. What this means is, as there is no cure for most cancers, the best we can do is to use treatment methods which in combination, slow down the disease process to a pace that makes the condition a ‘long term treatable condition’. The aim is to be able to put ‘brakes’ on the disease to turn into something that can be managed, rather likerheumatoid arthritis. Its not pleasant when somebody suffers but by careful management patients can achieve a quality of life which is something they find an acceptable ‘trade off’ between taking medication and the resulting outcome, whatever the outcomes are.

This has to be seen in context. The most difficult cancers to treat are tricky because they find collateral pathways to continue their ‘growth plans’ (the cancer cell) whatever treatment modality is used, the cancer can eventually find a way to achieve it aim of further replication. This is why survival (termed overall survival in cancer terms) is the Holy Grail of treatment. After all survival is the ultimate measure of treatment success and the ultimate need for patients facing life threatening health issues. Overall survival is an obvious measure of treatment success but as already stated, cancer is a complex disease to manage and sadly, overall survival is infrequently achieved. This means there has to be other measures of clinical outcomes outside of survival because cancer is incurable and we are seeking to ‘manage’ it as best we can. The main treatment milestones in most oncology studies are Survival (OS) Progression free survival (PFS) Stable disease (SD) and Progression (P) An explanation is offered below.

Overall survival

Overall Survival is the time that a cancer patient remains alive as a result of treatment for their disease. (Example shown later) This can vary from a matter of months to years depending upon which cancer is involved.

Progression Free Survival (PFS)

Progression Free Survival is different to Overall Survival. This term refers to the period within a disease journey, where a patient enters a period where they have not achieved ‘cure’ as they still have their disease but as a result of treatment or sometimes naturally, the natural progression of their disease has halted for a period of time where the disease doesn’t get any worse, hence the term Progression Free Survival.

Progression Free Survival is usually a finite period of time within the treatment/disease journey and in most cases, usually ends with signs that the symptoms of the disease return signaling the end of this period (PFS)

Stable Disease

Stable Disease is a term, which indicates the state in which a cancer has been treated and clinical signs of disease do not appear to ↑ or ↓ in extent or severity. Stable disease can vary from study to study and ranges from weeks or  months to years (infrequently) This term is quite often confusing to lay people but it is a very valuable state to be in if you are a patient undergoing treatment. Patients can gain an acceptable quality of life in Stable Disease during their cancer journey.

Progression

Progression is the term used when clinical indicators suggest the tumor is once again active. This means the treatment has either stopped working, or it is still working but the cancer has found an additional pathway to start growing again. This usually means adding further treatment lines or an adjustment to dose. Frequently, progression means that treatment has achieved as much as it can and will probably mean that active treatment is of limited value at this stage.

Objective response rates

This term refers to the % of patients who actually demonstrate a response to any therapy they have been subjected to. Any patient who has demonstrated any type of tumor response has received an Objective Tumor Response. Clearly the higher the percentage figures the more patients will be likely to get a response from the treatment.

Palliation or palliative care

This term refers to the stage where all active treatments have been explored and for whatever reason, have ceased to bring any meaningful value to the patient. Palliation is the managing of patient’s pain and psychological states when active treatment is no longer appropriate.

A properly constructed clinical study in oncology will normally feature these terms as they are the standard terms used to study and determine if a treatment has value. New treatment needs to meet the standards set out in the Study Protocol, which will usually be comparing one drug (an older or contemporary with a new or proposed drug)

If new treatments have not been through this rigorous process they have not shown that any treatment observations were as a result of using the drug as opposed to chance or previous treatments.

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