The performance status is a measure of how well an individual suffering from cancer is. It takes into account the extent of symptoms of cancer, how comfortably an individual can perform daily activities, and how much help he or she requires for basic self-care. The performance status is measured by a performance score that takes into account all of these factors.
Though it may sound like a rather vague thing to measure, the performance status is an extremely important issue in many aspects of cancer management. It has great impact on an individual's prognosis, on what cancer treatment he or she is likely to tolerate and, therefore, what treatments can be offered. Individuals with a poor performance status often fare worse than others with the same cancer stage and disease extent.
Performance scores are very often used to select patients for clinical trials. For example, a trial testing an intensive new treatment may only include patients who have a good performance score and are likely to be able to tolerate the treatment.
There are several scoring systems for performance status. The commonly used ones are the 'Karnofsky Performance Score (KPS)', the 'ECOG performance score', and the very similar 'WHO performance score'.