(114) The effect of pain on physical functioning after breast cancer treatment: development and validation of an assessment tool

Abstract

Sequelae after treatment for breast cancer such as persistent pain, musculoskeletal pain, sensory disturbances and lymphedema are major clinical problems. However, there is little evidence on how these sequelae affects physical function. Quality of life scales are designed to measure reduced physical function, while the influence of each sequelae is not measured directly. In order to enhance research in the rehabilitation of specific sequelae, the aim was to develop and validate a specific tool for assessing the causes of reduced physical function after breast cancer treatment. Literature review, patient and expert interviews were used to identify dimensions of physical function and sequelae. An item bank was developed and tested using cognitive interviews with patients and health care professionals. In a cross-sectional design the item set was field tested among 389 patients treated for primary breast cancer without recurrence (response rate 81%). Median follow-up was 14 months. Construct validity was assessed using Rasch analyses, and identified 5 cause scales of reduced physical functioning; pain after surgery, musculoskeletal pain, sensory disturbances, lymphedema and other causes. Convergent validity was assessed using the “Quick - disability of arm, shoulder and hand” scale (Q-DASH).About half of the patients reported decreased physical function, and each of the scales revealed different information on causes of reduced function. All 5 scales fulfilled common criteria for construct validity; good fit, unidimensionality, monotonicity, local independence, and lack of differential item functioning (DIF), as well as good correlation to single items on specific sequelae and Q-DASH. Cronbach coefficient alpha ranged from 0.88 (other causes) to 0.96 (sensory disturbances) for the 5 scales. Thus, the presented scales may be used to evaluate the causes of reduced physical functioning after breast cancer and may be useful to monitor and target interventions to optimize rehabilitation. Sequelae after treatment for breast cancer such as persistent pain, musculoskeletal pain, sensory disturbances and lymphedema are major clinical problems. However, there is little evidence on how these sequelae affects physical function. Quality of life scales are designed to measure reduced physical function, while the influence of each sequelae is not measured directly. In order to enhance research in the rehabilitation of specific sequelae, the aim was to develop and validate a specific tool for assessing the causes of reduced physical function after breast cancer treatment. Literature review, patient and expert interviews were used to identify dimensions of physical function and sequelae. An item bank was developed and tested using cognitive interviews with patients and health care professionals. In a cross-sectional design the item set was field tested among 389 patients treated for primary breast cancer without recurrence (response rate 81%). Median follow-up was 14 months. Construct validity was assessed using Rasch analyses, and identified 5 cause scales of reduced physical functioning; pain after surgery, musculoskeletal pain, sensory disturbances, lymphedema and other causes. Convergent validity was assessed using the “Quick - disability of arm, shoulder and hand” scale (Q-DASH).About half of the patients reported decreased physical function, and each of the scales revealed different information on causes of reduced function. All 5 scales fulfilled common criteria for construct validity; good fit, unidimensionality, monotonicity, local independence, and lack of differential item functioning (DIF), as well as good correlation to single items on specific sequelae and Q-DASH. Cronbach coefficient alpha ranged from 0.88 (other causes) to 0.96 (sensory disturbances) for the 5 scales. Thus, the presented scales may be used to evaluate the causes of reduced physical functioning after breast cancer and may be useful to monitor and target interventions to optimize rehabilitation.