Adaptation and initial psychometric validation of the Latvian version of EORTC QLQ-C30 and QLQ-BR45 in women with breast cancer.

PURPOSE: To culturally adapt and initially evaluate the psychometric properties of the Latvian versions of the EORTC QLQ-C30 and breast cancer-specific EORTC QLQ-BR45 in women with breast cancer. METHODS: The study was conducted within a pilot project implementing the ICHOM Breast Cancer Standard Set in a specialised university hospital in Latvia. Translation and cultural adaptation followed the EORTC procedure and included expert review and cognitive debriefing. Psychometric evaluation used baseline data from 142 women and six-month follow-up data from 47. Analyses included item-level indicators, internal consistency, multitrait scaling, inter-scale correlations, correlations with the Stress Symptom Scale, and paired change analyses. Conditional QLQ-BR45 items were treated as structurally missing when not applicable. RESULTS: Expert review and cognitive debriefing supported linguistic, conceptual, and cultural appropriateness. Reliability and item-scale correspondence were acceptable for several domains, with particularly strong multitrait scaling results for QLQ-BR45 Body Image, Sexual Functioning, and Breast Symptoms. Correlations between EORTC functioning and symptom domains and the Stress Symptom Scale were generally in the hypothesised directions. Six-month findings showed clinically plausible changes in functioning and treatment-related symptoms, but estimates were based on a smaller follow-up sample and reduced valid samples for some conditional scales. CONCLUSION: The Latvian EORTC QLQ-C30 and QLQ-BR45 showed acceptable preliminary psychometric performance. The findings provide initial support for their use to assess HRQoL and breast cancer-specific symptoms in Latvia, while larger multicentre and longitudinal studies are needed to evaluate additional measurement properties and responsiveness.