Patients with throat cancer who are positive for the human papillomavirus (HPV) have a good prognosis, but until now the effect of being HPV-positive on the prognosis of other head and neck cancers (HNC) was unknown.
Danish researchers have shown that HPV status appears to have no prognostic effect on the outcome of primary radiotherapy in HNCs outside the oropharynx, according to a study presented at European Society for Radiotherapy and Oncology (ESTRO) meeting, being held in Vienna, Austria.
Researcher Pernille Lassen, MD, PhD, from Aarhus University Hospital in Denmark, said HNCs located outside the oropharynx should probably not be treated with the less intensive treatment strategies that are currently being investigated in clinical trials for HPV-positive oropharyngeal tumors.
"HPV status has a very potent prognostic impact in radiotherapy for oropharyngeal cancer, and DNA from HPV has been found in all types of head and neck cancer, although it is far more common in oropharyngeal tumors," Dr. Lassen said.
The researchers investigated the impact of HPV status in nonoropharyngeal cancers in a database of Danish HNC patients. The study group included patients with locally advanced cancers who had been treated primarily with radiotherapy, and the researchers identified 1,606 patients with larynx and pharynx carcinomas. Overall, 40% of the tumors were HPV-positive, and the frequency was significantly higher in oropharyngeal cancer (57%) than in nonoropharyngeal (13%).
Being HPV-positive significantly improved tumor control (81% versus 55%), as well as survival from the cancer (89% and 55%, respectively) and death from any cause (82% and 38% respectively) after five years.
"In nonoropharyngeal cancers, we found no prognostic impact of being HPV-positive in any of these end points," Dr. Lassen said. "This indicates that HPV status does not help us in predicting response to treatment, and hence the outcome of these cancers."
"We know from laboratory studies that HPV-positive tumor cells are much more sensitive to radiation therapy than HPV-negative cells, so until now we believed that they would behave similarly irrespective of site," Dr. Lassen explained. "However, these data indicate that this is not the case, and at present we do not understand why this should be."
There could be biological and/or genetic differences other than HPV status between the tumors, the researchers said. For example, they could result from genetic changes caused by smoking tobacco, differences due to tumors of mixed makeup (for example, a combination of HPV and tobacco), or perhaps simply differences due to the site.
"We have started following up our work by analyzing all the tumor samples using polymerase chain reaction, a way of amplifying DNA in order to be able to analyze changes in genetic information. We hope this will enable us to understand more about why the role of HPV in nonoropharyngeal tumors is so different. There are few data available on this subject at present, so finding out will be an important step toward optimizing treatment for these patients."
ESTRO President Vincenzo Valentini, MD, a radiation oncologist at the Policlinico Universitario A. Gemelli in Rome, said the findings will have an important impact on the treatment of HPV-positive HNCs and will likely lead to changes in current treatment.
