155 8 Strengths and limitations The strengths of this study were the prospective study design, the large number of patients, and the use of the LMM checklist with recommendations for reporting multilevel data and analyses.45 Because only 35 patients received CO2 laser treatment, and these results were comparable to the results of patients that received surgery, it was decided to combine these groups. In addition, patients with a larynx and hypopharynx tumor were combined as well (n=205 and n=52 in the total NET-QUBIC population, respectively). A limitation of this study was the fact that only 374 patients filled in the questionnaire 2 years after treatment.32,33 The 739 patients that were included in the NET-QUBIC research are already a selection of the total HNC population, in which it is unknown whether the non-responders perform worse or better regarding swallowing problems. In addition, there was a relatively large group of patients with missing measurements at each time point (Figure 1). Another limitation of this study was that information about rehabilitation during or after treatment was not taken into account. Conclusion Patients with HNC reported an increase in swallowing problems from baseline to 3 months after treatment, and a slow decrease from 6 months onwards with return to baseline level. The subscale eating duration of the SWAL-QOL showed the most problems after treatment. A longer eating duration was associated with female sex, smoking and weight loss at time of diagnosis, having tumor stage III or IV, and being 3 to 6 months after treatment. Especially patients with an oropharynx and oral cavity tumor showed a persistent increase in eating duration. In addition, patients receiving (C)RT following surgery, and patients receiving CRT only showed the worst decline in outcomes, which did not return to baseline levels after treatment.