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Chapter 4
Quality of life related outcomes
Symptom related quality of life questionnaires were used. The Dutch version of the SWAL-QOL, a validated 44-item questionnaire on dysphagia and its influence on daily life, was assessed. All scores range from 0 to 100 with higher scores indicating more dysphagia-related problems, and scores ≥ 14 points indicating swallowing problems in daily life (36-38). Subjective speech and voice function were assessed by means of the validated Dutch versions of the Voice Handicap Index (VHI) and Speech Handicap Index (SHI), respectively. These are both 30-item voice/speech-related quality of life questionnaires with higher scores indicating more speech/ voice-related problems (39-42). A VHI score of 15 or higher, and a SHI score of 6 or higher indicate voice, respectively speech problems in daily life (38, 43).
Also, overall quality of life was assessed by means of the EQ-5D-5L. The EQ-5D-5L includes the following five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/ depression. Each dimension has five levels of severity ranging from no to extreme burden. We dichotomized outcomes in to any burden (slight, moderate, severe, unable to perform) and no burden. The five dimensions are completed by the EQ-VAS, which records the patient’s self- rated health on a visual analogue scale ranging from worst (0) to best (100) health.
Statistical analysis
Analyses were performed using IBM® SPSS® Statistics 23.0 and R 3.6.2. Baseline characteristics and outcomes at both six and ten years after treatment were presented using descriptive statistics. Medians and ranges were used for numerical and ordinal variables. For proportions, the Wilson score 95% confidence intervals were calculated. For medians, bootstrapping was used to estimate 95% confidence intervals. For comparison, outcomes at six-year follow-up are described only of the 14 patients evaluable at ten-year plus follow-up. With the small sample size of this study, which was inevitable for the given patient population, only very large changes will be statistically significant using the traditional cut-off of p = .05 for statistical significance. Also, absence of statistically significant changes cannot be interpreted as evidence for no change. We therefore consider these results to be descriptive, rather than inferential, and accordingly we refrained from hypothesis testing. Instead, we interpret the measurements based on their clinical meaning for the individuals in the sample.