Appropriate time frames for data collection in quality of life research among cancer patients at the end of life.

Longitudinal research has been recommended as the most appropriate research design to ensure the validity of quality of life assessments. However, high attrition and non-random missing data in quality of life studies for terminal cancer patients raise questions about generalizability of the study, and at worst they may jeopardize interpretation of the results. Appropriate time frames for eliciting information directly from terminal cancer patients can ensure the internal and external validity of quality of life research in end-of-life care, allow health care professionals to detect sensitively the effects of end-of-life care within the shortest intervention period, and make comparisons across studies possible. From a review of the literature, it is recommended that the appropriate time frame for interviewing terminal cancer patients about their quality of life be a weekly assessment schedule based on the following factors: (a) the median survival of terminal cancer patients enrolling in a hospice/palliative care program is approximately 30 days and there are substantial number of patients who die in each week; (b) at the final weeks of life, quality of life and symptoms of some terminal cancer patients change dramatically; and (c) the shortest intervention period that is likely to give a clinically significant effect of end-of-life care management is 1 week after the enrollment in end-of-life care.