Visual analogue scales and assessment of quality of life in cancer.

Assessment of quality of life (QOL) in cancer clinical trials is important when comparing treatments, especially when prolonged survival is not expected. QOL scores may reflect physical or psychosocial functioning or distress. The choice of QOL instrument depends upon the definition, research hypothesis, cancer population, depth and sensitivity of information required, and frequency of measurement. A visual analogue scale (VAS) is commonly used to rate various subjective experiences. Potential advantages of these scales include their wide score range and high sensitivity; disadvantages include lower completion rates than other rating scales. Single-item VASs are validated for cancer QOL, reliable, and responsive to change. These scales may best represent an individual's global QOL without the constraints of predetermined domains. Single items are useful for frequent measurements in palliative or advanced populations and when information about domains is less important. Multi-item VAS QOL instruments vary in length and domains; they are useful in clinical trials enrolling patients with good performance status, but some are long and disease-specific.