Discussion:
We report a case of synchronous p16+ SCC involving the BOT and nasopharynx. To our knowledge, this is one of only two reports of synchronous HPV associated SCC involving the oropharynx and nasopharynx(3). There are however, reports of metachronous p16+/HPV+ NPC diagnosed following prior OPC treatment, raising the possibility of occult primaries lying within the nasopharynx in these cases (2).
This case presented a diagnostic dilemma. There was not uniform agreement at our multi-disciplinary meeting and it was questioned whether the initial biopsies had been mislabelled given the panendoscopy (and negative biopsy) and MR findings of an obvious tumour in the BOT. Although the FDG-PET/CT showed an abnormality in the nasopharynx, there was no corresponding structural abnormality and false positive FDG-PET/CT findings in the head and neck are well documented (4). The repeat panendoscopy and PET/CT with corresponding reduction in SUV further challenged the presence of a nasopharyngeal primary, but nasopharyngeal adenoidectomy was felt to be prudent given a degree of uncertainty, which confirmed a synchronous p16+ NPC.
While treatment of the nasopharynx was possible from the outset, treating both the BOT and nasopharynx without sufficient proof will almost certainly subject a patient to excessive long-term toxicities, including lifelong dysphagia and possible feeding tube dependence. Indeed, in this case a mean dose of 62Gy was delivered to the pharyngeal constrictors which is associated with higher chances of long term swallowing problems (5). In contrast, failing to treat the nasopharynx at the outset would likely lead to an unsalvageable recurrence. Just like the proposed recommendation by McGovern et al, we also recommend care full physical examination and biopsies in case of increased uptake on PET scan (3). While synchronous or metachronous p16+ OPC and NPC are rare, it is also possible that the elective coverage of level two, retropharyngeal and retrostyloid nodes will result in a dose wash through the nasopharynx which might be sufficient to eradicate microscopic disease.
International consensus guidelines on radiotherapy target volumes exist for both NPC and OPC. There are however, no guidelines on the optimal management of synchronous p16+ primary HNC. While OPC cases are typically treated with isometric expansions (5+5mm) from gross disease with elective coverage of nodal volumes, NPC treatment paradigms are largely based on outcomes from EBV+ cases, mandating widespread elective coverage of the base of skull. Whether this wide field coverage is necessary in HPV+ NPC cases is not currently known, but warrants further investigations.
In conclusion, we reported a unique case of synchronous p16+ SCC involving both the BOT and nasopharynx. In the setting of a relatively normal appearing nasopharynx on MRI, PET/CT may be useful in detecting occult p16+ SCC in the nasopharynx and should guide more extensive sampling, which may include adenoidectomy in selected patients.