Distant metastasis in head and neck cancer—specifically head and neck squamous cell carcinoma (HNSCC)—is an ominous sign. While patients with certain cancer types who have distant metastases can live a long life (well-differentiated thyroid cancer, some adenoid cystic salivary gland carcinomas), many others will have complications related to the cancer. In general, the goal of managing distant metastasis is to try to prevent the tumour from growing and causing complications.
Certain tumour types are more likely than others to develop distant metastases. This includes adenoid cystic carcinoma, basaloid squamous cell carcinoma and neuroendocrine carcinomas (such as Merkel Cell carcinoma).
The exact incidence of distant metastases in head and neck cancer is difficult to determine. Historically, there was a long-standing belief that the lymph nodes in the neck were a barrier preventing cancer from spreading throughout the rest of the body. This was based on autopsy studies of patients who died with HNSCC; in over 4000 autopsies, the rate of distant metastasis was less than 1 percent. Whether the lymph nodes in the neck are a necessary step prior to cancer getting to distant sites is a matter of debate, and newer studies have shown that the rate of distant metastases can be as high as 25 to 50 percent in autopsy studies of patients with HNSCC.
According to a thorough analysis of information over many years, the following trends in stage at diagnosis of a few different types of head and neck cancers showed the following:
|Site||Percentage of patients with distant metastasis at diagnosis 1974 to 1999|
Over the past few decades, doctors have made big advancements in eliminating the main tumour and spread to lymph nodes in the neck, which is called locoregional control. However, long-term survival has not changed significantly. One possible reason for this is while locoregional control has gotten better, the rate of distant spread of the cancer has not changed (or may have even increased as patients with locoregional control live longer). As it stands, while local and regional control of head and neck cancer is necessary to achieve a cure, it is not enough. There is something inherent tumours that makes them more likely to spread throughout the body.