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Chapter 2
DISCUSSION
This is the first study to compare self-reported swallowing function in people with early- stage OPC who are offered single-modality treatment with surgery or RT. Existing prospective data from 300 participants in the multi-institutional HN5000 study were used, with 150 participants offered surgery and 150 offered RT. Trismus was more prevalent in participants offered surgery. However, participants offered surgery had better other functional outcomes including swallowing, dry mouth and altered taste, compared to those offered RT, both at 4- and 12-month follow-up. This difference was more prominent when comparing participants who received their intended single modality surgery or RT. This was probably because 52% of the participants offered surgery received adjuvant treatment while 84% of those offered RT received their intended single modality treatment. There was no evidence of a difference in survival between surgery and RT. Differences in swallowing problems, however, did not result in substantial differences in tube feeding use.
The 150 participants offered surgery were younger, had less comorbidities, earlier tumour- and, TNM-stage and had less pre-treatment swallowing problems compared to the 150 offered RT. However, despite these baseline differences, adjustment for these confounders resulted in only modest attenuation of RRs. It is possible that these baseline characteristics contributed to treatment selection offering participants with favourable baseline characteristics surgery more often. In addition, participants selected for surgery have more favourable characteristics not captured by the measured confounders such as tumour volume or the distance from tumour to swallowing structures, than participants offered RT. Even in the T1N0 participants, these T1 tumours may have had other characteristics not adjusted for, such as tumour volume or location near swallowing related structures. While the lack of attenuation on adjustment is reassuring, randomized trials are required to exclude the possibility of residual confounding.
Previous observational studies have shown that people who are offered surgery only for early- stage OPC are likely to receive adjuvant treatment (4, 9). Also, studies have shown that adjuvant treatment after surgery for oropharyngeal cancer is associated with a decreased quality of life and cost-effectiveness (26-29). In our cohort, 52% of participants offered surgery received adjuvant (C)RT and they reported comparable functional impairments to participants treated with RT only. Our study confirms that the favourable functional outcomes in people offered surgery, are only present when adjuvant treatment is avoided.
The indications to use adjuvant RT are not well defined. In general, in the case of close resection margins, re-excision is favoured over postoperative RT. In the case of neck metastases, a single metastasis is often treated with a selective neck dissection, but multiple lymph node metastases are usually seen as an indication for postoperative RT (30). However, in the case of HPV positive tumours, multiple lymph node metastases without extranodal spread are staged as N1, and the role of postoperative RT has not been well defined (31).