May 12, 2008 -- Researchers have discovered that throat cancers linked to the human papillomavirus (HPV) respond better to cancer treatments than cancers not associated with HPV, a finding that's being lauded as a promising step toward tailored treatment.
Thomas Carey, PhD, professor and distinguished research scientist at the University of Michigan Kresge Hearing Research Institute and co-director of the head and neck oncology program at the University of Michigan Comprehensive Cancer Center, and colleagues published their results in two papers in the May 12 online issue of Journal of Clinical Oncology.
Most throat cancers, or oropharyngeal cancers, occur in people who smoke or chew tobacco. However, certain strains of HPV, including one known to cause cervical cancer, play a role in the development of some throat cancers. According to the American Cancer Society, people with throat cancers linked to HPV are less likely to smoke and drink, and generally have better survival rates.
"The biggest challenge is how best to treat patients with tumors that stem from tobacco and alcohol use as opposed to tumors linked to HPV. We now know they're two different cancers," study researcher Francis Worden, MD, assistant professor of internal medicine at the University of Michigan Medical School, says in a news release.
Scientists blame HPV infection for a recent rise in throat cancer cases, particularly among younger patients, according to background information in the journal article.
The current study involved 66 patients with advanced throat cancer. Each study participant received an initial round of chemotherapy to determine how well the tumor responded to the cancer-killing medication. If the treatment reduced the tumor by more than half its original size, the patient received radiation and a full course of chemotherapy.
The first round of chemotherapy successfully shrank the tumor in 54 patients, and most of these patients went on to receive additional chemotherapy with radiation. After four years, 62% of those patients were still alive. Most of the patients had surgical treatment of their cancers if their tumor did not respond to the first round of chemotherapy. Only four of the 11 patients who did not respond to the first round of chemotherapy survived.
The researchers' next step was to determine why chemoradiation failed to work in a subset of patients. They looked at tissue samples taken from patients before treatment and found that 64% tested positive for a high-risk strain of HPV (HPV 16). The team's analysis showed that most of the HPV-positive tumors responded to the first round of chemotherapy. Only four patients with HPV-negative tumors survived.
The experiments also revealed that patients with tumors that give off high levels of a certain growth factor receptor called EGFR had the poorest survival rates.
"The combination of markers was an important indicator. Patients whose tumors expressed high levels of EGFR did poorly. But those who had high EGFR and were also HPV-positive had some protection. Patients with high EGFR and low HPV fared the worst," Bhavna Kumar, a research laboratory specialist and study co-author, says in a news release.
Study authors say their findings have large implications for therapy.
"The chemotherapy and radiation therapy we use to treat this type of cancer is very aggressive. If we can identify those patients most likely to respond, we could reduce the intensity of the therapy for those likely to have the best outcomes. At the same time, we hope to identify new treatments that specifically target those tumors that we know are not responding to current therapies," Carey says.