Dimensions of fatigue during radiotherapy--an application of the Swedish Occupational Fatigue Inventory (SOFI) on cancer patients.

The aims of this study were primarily to evaluate the applicability of the Swedish Occupational Fatigue Inventory (SOFI) on cancer patients, secondly to describe the development of fatigue in patients, receiving full dose radiotherapy with a curative intent. A questionnaire was completed by 81 cancer patients at four occasions; before treatment. during the last week of treatment. 1 and 3 months, respectively, after treatment. The fatigue increased significantly at the end of treatment, as compared to pretreatment, and decreased after treatment. The highest fatigue ratings concerned lack of energy, lack of motivation and sleepiness. The five SOFI-dimensions explained more than half of the variance in the overall rating of fatigue, and the internal consistency of the dimensions were good. However, the ratings were on the lower part of the scale and the dimensions correlated more than expected. Thus, the relevance of the SOFI for use also among patients is only partially supported, and studies with larger samples are needed for further testing of the inventory.