GRACE :: Cancer Basics


Dr West

FAQ: What is “Performance Status” and Why Does it Matter so Much?

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Along with a patient’s age, sex, and past and current medical issues, performance status (PS) is one of the most important factors that is categorized for patients. It essentially refers to a patient’s ability to manage his or her activities of daily living — things like bathing, dressing, feeding yourself, etc., as well as general activity level and ability to do whatever work they need to do. 

There are two leading scales for measuring PS. The most frequently used one, known as the Zubrod or ECOG scale,  simply goes from 0 to 4, with 0 representing no symptoms or limitations, and 4 representing being bedridden and completely unable to care for yourself.  

Zubrod PS


The alternative is called the Karnofsky PS scale, describing the range of activity from fully functional (100%) down to 10%, bedridden; obviously, this is essentially the same range, but with finer grading, as if you could assign half points on the Zubrod scale. Here’s the description of the levels on the Karnofky scale:

Karnofsky Performance Status PS Scale

Though this scale suggests that there is a clear number for everyone, it is more fair to acknowledge that PS is somewhat in the eye of the beholder.  Certainly, one person’s 70% Karnofsky PS may be 60% to someone else, and this may depend on how well a person happens to be doing on a given day at a given hour.  This may be part of why the Zubrod PS scale is more widely used: it doesn’t put too fine a point on a subjective measure.

The reason PS is so important is that it is predictive of how a patient will do with and without treatment for cancer. In fact, it is more predictive of prognosis and ability to tolerate the rigors of potentially challenging anti-cancer therapy than other intuitively relevant factors like a patient’s chronologic age. A fit 78 year-old is likely to fare better than a frail 67 year-old, either with or without treatment. Moreover, since many cancer treatments will lead to difficult adverse effects, therapies that are feasible and beneficial for a patient with a PS of 0 or 1 may be more likely to be harmful for a patient with a PS of 2 and is very likely to be prohibitively, overwhelmingly toxic to a patient with a PS of 3 or 4.  While the majority of cancer treatments have been far better studied in patients with a good performance status, there are now a growing number of trials specifically for patients with a more marginal PS, in light of the reality that up to 1/3 of the patients in the “real world” of community-based cancer care are in the more frail range of PS.

It is important to recognize that PS is dynamic. For someone with an advanced/metastatic cancer, the overall trajectory of progressing cancer and cumulative side effects of treatment typically lead to a gradual worsening of a patient’s PS over time. On the other hand, patients can also be very symptomatic and limited by their cancer, then experience a dramatic improvement in PS if treatment is effective.

Overall, PS is a critical variable, and it is important to ensure that the therapies being pursued are appropriate for that patient’s PS, in order to give them the best chance of doing well against their cancer without the treatment being worse than the disease.

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