Discussion
The role of oesophagoscopy in HNSCC had been debatable in the literature. Amongst North American studies, the rate of synchronous malignancies in oesophagus ranged from 0-8% in most studies in the 1980s. However, in a review by Mcgarey et al14, there had not been a single synchronous oesophagealmalignancy detected on staging oesophagoscopy for patients with HNSCC since 2000 in North American studies. In contrast, most studies fromTaiwan and Hong Kong however had found significant rates of synchronous oesophagealmalignancies among patients with HNSCCs. Chow et al15 reported a rate of 10% for clinically important oesophageal lesions found among 118 HNSCC patients undergoing oesophagoscopy for workup. Chung et al6 and Huang et al16 reported 23.3% and 14.8% synchronous oesophagealmalignancies among patients with HNSCCs respectively in their studies. These findings could be explained by the relatively higher prevalence rate of oesophagealmalignancies in Asia17and the high prevalence of habits of chewing betel nuts in Taiwan16,18, which is a common carcinogen for both oesophagealmalignancies and HNSCCs.
In our study, the rate of occurrence of synchronousoesophagealmalignancies was 5.8% (41/702) and out of these 41 lesions, 14 of them were onlydetectable by oesophagoscopy, i.e. these malignancies would be otherwise missed by other means of investigation (e.g. CT/PET-CT). 4 of these 14 patients were asymptomatic. In addition, most of these malignancies (13/14) found were of early stage (stage 1 cancers). The overall survival and disease-free survival of patients with malignancies exclusively detectable with oesophagoscopy were significantly better when comparing with other synchronousoesophagealmalignancies not exclusively detectable with oesophagoscopy (P = 0.028).This had highlighted the importance of staging oesophagoscopy in screening out synchronous oesophagealmalignancies. It is also effective in screening out early stage disease and potentially benefit patient’s survival.
Inour study, the risk factors associated with development of synchronousoesophagealmalignancies included male gender, smoker/drinker status and primary hypopharyngeal cancer.Anatomically, the hypopharynx and oesophagus are structures connected continuously and there had been proven association between malignancies from both structures16,18-21. Huang et al16evaluated 248 patients with hypopharyngeal cancers prospectively and reported a rate of 14.8% of synchronous oesophageal cancers and 9.4% of oesophageal dysplasia among the patients. The French ENT society concluded in their 2012 guideline that oesophagoscopy was indicated as staging procedure for patients with hypopharyngeal cancers22.
As the field cancerization theory2 suggested, alcohol consumption and tobacco use are risk factors for development of synchronous malignancies in the upper aerodigestive tract. Lower rates of synchronous malignancy development among non-smokers or non-drinkers was found in studies23,24. Alcohol drinking was reported to be associated with increased risk of oesophagealmalignancy in a study for patients with HNSCCs6 (OR:5.90, P = 0.020), as well as an independent risk factor for development of oesophagealcancerous or dysplastic lesions in hypopharyngeal cancer patients16 (OR: 6.95, P<0.05). The French ENT society suggested that oesophagoscopy should be indicated for patients with chronic alcohol intoxication as it increased the risk of development of synchronous oesophagealmalignancies22.
Bronchoscopy had been less utilized as a routine screening procedure for synchronous lung malignancies in patients with HNSCC when comparing with oesophagoscopy. This could be due to the availability of other non-invasive means of screening modalities such as chest x-ray, CT scan of the thorax and PET-CT imaging. There was also a low yield of bronchoscopy in the literature as a screening modality for HNSCC patients, ranging from 0-1%21. In our study, the rate of synchronouslung malignancies was at 0.6%, comparable with the literature. Amongst them, non-of them is exclusively detectable with bronchoscopy and all of them can be detectable on PET-CT, suggesting that bronchoscopy can be potentially replaced by other investigative modalities.