HPV tumor status did not determine radiotherapy outcomes in head and neck cancer

HPV tumor status does not appear to prognostically affect the outcome of radiotherapy treatment among patients with non-oropharyngeal carcinoma head and neck cancer, according to findings reported at the Congress of the European Society of Radiology and Oncology.

In the analysis, researchers identified for study 1,606 patients from the DAHANCA database. All selected patients had stage III to IV larynx and pharynx carcinoma and underwent a regimen of primary radiotherapy, aimed to be curative, between 1999 and 2012.

Immunohistochemistry was used to evaluate pretreatment tumor blocks for expression of HPV-associated p16. They were categorized as positive in the event of strong and confluent cytoplasmic and nuclear staining in less than 70% of tumor cells.

The investigators found that 646 (40%) of the tumors were p16-positive, and the prevalence of p16 positivity was significantly higher in patients with oropharyngeal carcinoma (57%) than in non-oropharyngeal carcinoma patients (13%; P<.0001).

Among patients with oropharyngeal carcinoma, researchers noted a significant, positive correlation between p16 positivity and improved locoregional tumor control (5-year actuarial values, 81% vs. 55%; adjusted HR=0.44; 95% CI, 0.34-0.59), disease-specific survival (89% vs. 54%; HR=0.29; 95% CI, 0.21-0.4) and OS (82% vs. 38%; HR=0.32; 95% CI, 0.25-0.42) vs. p16-negativity.

In patients without oropharyngeal carcinoma, p16 positivity was not related to any prognostic effect locoregional tumor control, disease-specific survival or OS.

Study investigator Pernille Lassen, MD,of the Aarhus University Hospital in Denmark, said these findings were unexpected in terms of the previous understanding of HPV-positive tumor cells.

“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,” Lassen said in a press release. “However, these data indicate that this is not the case, and at present we do not understand why this should be, though it probably can be ascribed to other biological/genetic differences between the tumors rather than the HPV status. We would now like to try to elucidate the underlying mechanisms behind these different outcomes.”

For more information:

Lassen P. Presented at: European Society for Radiotherapy and Oncology (ESTRO) 33 Conference; April 4-8, 2014; Vienna.

Disclosure: The researchers report no relevant financial disclosures.