Strengths and limitations of the study
The main study limitation is the retrospective design. Another limitation is that we did not examine symptom duration prior to the first visit, mainly due to missing data. Although there were some restrictions in outpatient visits and delays in the start of radiotherapy, none of the units had to be closed for more than 2-3 days and none of the doctors had to be transferred other hospitals to treat Covid-19 patients. A final limitation is that we did not assess or compare patient outcomes. By contrast, an important strength of this study is that it is, to our knowledge, the first to examine the effect of the pandemic on patients with head and neck cancer during an extended time period (12-months) comprising several waves of the pandemic.