An international field study of the reliability and validity of a disease-specific questionnaire module (the QLQ-OV28) in assessing the quality of life of patients with ovarian cancer
Introduction
The standard approach for treating patients with ovarian cancer is surgery followed by chemotherapy. For women with early stage disease, surgery is potentially curative and 5-year survival rates are around 70% [1]. However, they are at a high risk of recurrence and may therefore be advised to accept adjuvant chemotherapy. Most patients present with more advanced disease, with 5-year survival rates around 30%. Over the past 20 years, different combinations of cytostatic drugs including different doses and modes of delivery have been tried to optimise treatment gain and reduce toxicity. The combination of platinum-paclitaxel is internationally accepted as first-line management for advanced ovarian cancer following the results of two randomised trials 2, 3, consensus statements from the United States (US) [4] and the United Kingdom (UK) 5, 6 and an international consensus meeting [7]. High response rates to first-line treatment can now be achieved, but still at a cost in terms of unpleasant side-effects. There is now considerable research activity involved in order to try to optimise first and second-line treatments for patients with advanced or recurrent disease. Quality of life (QOL) outcomes are of particular relevance in evaluating palliative treatments 8, 9. Most patients with advanced disease will relapse, often with disease resistant to the first-line agents they have received. With a growing emphasis on the need for evidence-based practice and for involving patients in treatment decision-making, patient-reported QOL outcomes have become important and should be more frequently assessed in ovarian cancer trials. The measure used should cover the predominant disease- and treatment-related issues.
The QLQ-C30 core questionnaire—developed by the European Organisation for Research and Treatment of Cancer (EORTC) QOL Group—is a psychometrically robust, cross-culturally accepted questionnaire, which was designed to be applicable to a broad spectrum of cancer patients [10]. It has been validated for ovarian cancer patients [11] and recommended by independent reviewers for use in clinical and research settings [12]. The EORTC QLQ-C30 measure (version 3.0) consists of five function scales: physical, role, emotional, cognitive and social; three symptom scales: fatigue, nausea/vomiting and pain; six single-item scales: dyspnoea, sleep disturbance, appetite loss, constipation, diarrhoea and financial impact; and also a global QOL scale. The EORTC Quality of Life Group measurement strategy is to supplement the core EORTC QLQ-C30 with disease- and/or treatment-specific modules to address additional issues.
The EORTC QLQ-OV28 module contains issues of relevance to the QOL of patients with ovarian cancer and was developed in a multicultural setting. The detailed development process of the module has been described elsewhere in Ref. [13]. The module has been translated into 14 languages (English, Croatian, Danish, Dutch, French, German, Italian, Portuguese, Spanish, Swedish, Taiwan-Chinese, Finnish, Norwegian and Polish) according to the EORTC QOL Group guidelines [14]. Although a shorter version of the module has been previously used in a single country phase III trial, in Scotland (SCOTROC) [15], the clinical and psychometric properties of the entire scale have not been formally tested. The aim of this international field study was to confirm the hypothesised scale structure and to determine the reliability, validity and cross-cultural applicability of the EORTC QLQ-OV28.
Section snippets
Patients and methods
The prospective study (EORTC protocol 15982) was activated in January 1999 and closed to patient recruitment in July 2001—was co-ordinated at the Quality of Life Unit at the EORTC Data Centre in Brussels, Belgium. Patients were eligible if they had a diagnosis of epithelial ovarian cancer, expected survival time of at least 3 months, and provided written consent to participate. Exclusion criteria were: concurrent malignancies, inability to understand and complete the questionnaire, or
Data collection
QOL assessments were conducted at various time points: Patients in Group 1 were asked to complete the questionnaire twice: prior to the start of the first cycle of chemotherapy and on the day of the fourth cycle of chemotherapy. Patients in Group 2 completed the questionnaire, at their first visit to the clinic after treatment (within 8 weeks of the sixth cycle of chemotherapy). Patients in Group 3 completed the questionnaire twice, the first time at a routine follow-up visit to the clinic and
Statistical analysis
It was considered important to include data from patients likely to experience side-effects of chemotherapy in the assessment of the validity of the scale. Therefore, data regarding the second assessment from groups 1 and 4 and the single assessment of group 2 were primarily used in the analysis. This population will be referred to as the ‘on-treatment population’. In total, this provided us with a limited number of patients (N=154). However, the analysis was repeated using baseline data from
Patient characteristics
A total of 368 ovarian cancer patients from six different countries were entered into the study. 57 patients were excluded, because the timing of the QOL assessment was outside of the specified time window of the study or patients did not return the questionnaires by post. Sociodemographic and clinical characteristics are shown in Table 1. Patients had different stages of ovarian cancer. More than half of the study participants were diagnosed with advanced stages of disease (FIGO stages III and
Summary statistics and distribution of items
The scale scores were standardised to a 0–100 range and missing items were replaced using a simple imputation as in other EORTC questionnaires [16]. Missing values were replaced by the mean of the other items in the scale if at least half of the data were present for that scale; otherwise the scale value was regarded as missing. The distribution of all the items and scales are presented in Table 2. The distribution of most items was skewed towards a lower response to the items. The summary
Discussion
The goal of new approaches to ovarian cancer treatment is to improve the quality, as well as the duration, of patients’ lives. The need to assess outcomes in terms of patients’ experience is increasingly recognised. Generic QOL measures do not adequately capture specific disease- and/or treatment-related issues which affect the QOL of women treated for ovarian cancer in international clinical trials. For this purpose, a questionnaire was developed to supplement the widely used EORTC QLQ-C30 for
Acknowledgements
We thank Christiane van Pottelberghe and Irina Ghislain for assistance with the Data Management. Verena Meraner, MSc Dept of Biological Psychiatry, for conducting the patient interviews in Innsbruck and all of the patients for helping us with this study.
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