The Bt-DUX: Development of a subjective measure of health-related quality of life in patients who underwent surgery for lower extremity malignant bone tumor

Background. To examine the practical applicability, internal consistency, and validity of the Bt-DUX, a disease-specific Health Related Quality of Life (HRQoL) instrument. The Bt-Dux was developed to examine patients' individual values of their life after a malignant bone tumor of the lower extremity at four domains (cosmetic, social, emotional, and functional). Procedure. Patients were eligible for this cross-sectional, multicenter study if they underwent surgery for a malignant tumor of the leg in a period ranging between 12 and 60 months before the recruitment. Assessments included: Bt-DUX, Toronto Extremity Salvage Score (TESS) Short Form (SF)-36, TNO-AZL Questionnaire for Adult's Quality of Life (TAAQOL), and TNO-AZL Children's Quality of Life Questionnaire (TACQOL). Results. Seventy-two patients (35 male, 37 female), mean age 17 (SD 4) years were included. Limb sparing surgery took place in 32 patients and ablative surgery in 40 patients. The Bt-DUX was completed in less than 5 min and easy to comprehend. The mean Bt-DUX score was 69.8 (SD 15.5), with Cronbach's alpha being 0.92. Domain-total correlations ranged between 0.84 and 0.88 (P<0.01). Correlations between Bt-DUX Total score and TESS, SF-36 Physical and Mental Component Summary scales and selected TACQOL and TAAQOL scores were statistically significant (P<0.05), except for the social scale of the TACQOL. The Bt-DUX was able to discriminate between patients with higher and lower TESS scores (P<0.05). Conclusion. The Bt-DUX was found to be a practical and valid instrument. Its added value compared with existing HRQoL measures needs to be further established.