Patients with SCCs of the upper aerodigestive tract are at high risk of developing a second primary tumour (SPT) at a separate anatomic site from the index (first) tumour. The SPT is synchronous if it is diagnosed within 6 months after the index tumour, or metachro-nous if it is diagnosed more than 6 months after the index tumour. Synchronous tumours are simultaneous if they are discovered at the same time as the index tumour.
The median prevalence of SPT in patients with an index tumour in the upper aerodigestive tract is 9% [149, 291, 337]. The site of the SPT is affected by the site of the index tumour. In patients with an index tumour in the oral cavity, pharynx and oesophagus, the SPT tends to arise in the same location. In patients with index tumours in the larynx, the SPT tends to be located in the lungs .
The risk of developing an SPT closely correlates with the use of tobacco and alcohol abuse, and is more than doubled in patients who smoke and drink compared with those who do not smoke and drink . Moreover, there is a direct dose-dependent relationship between tobacco and alcohol exposure and the risk of SPT.
It is now accepted that long-term exposure to tobacco and/or alcohol causes extensive and diffuse DNA changes leading to widespread genetic damage or "field cance-risation" of the whole respiratory tract and the upper digestive tract .
The prognosis for patients with SPTs is poor, being worse for synchronous SPTs than for metachronous tumours. They generally present with a more advanced T stage, and have a much lower 5-year survival than the index tumour .
It is therefore imperative for a panendoscopy to be performed at the time of diagnosis of the index tumour, not only as a part of the staging procedure, but also to look for an SPT .
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