Blood Test Predicts Effectiveness of HPV-Positive Throat Cancer Treatment

June 24, 2021 - A team of researchers at the University of Michigan Rogel Cancer Center are working on a promising new blood test that they say will be able to predict if patients with metastatic HPV-positive throat cancer will respond to treatment months earlier than standard imaging scans. Findings from this study were published in Oncotarget.

If the blood test works, doctors will be able to determine if a specific treatment is effective sooner. This will allow doctors to switch the treatment plan in a timely fashion if they are not seeing positive results, saving the patient months of needless toxic side effects.

"Currently, the only way doctors know if a treatment is working is for the patient to get an imaging scan every few months to see whether their tumors are shrinking," oncologist Paul Swiecicki, MD, one of the study's senior authors said in a press release.

"And this isn't fully accurate since some cancers show what we call pseudoprogression, where a successful treatment actually makes the tumors bigger before it shrinks them. Our goal was to develop a test that could tell us whether a treatment is likely to work after a single cycle,"Swiecicki said.

This research is coming as cases of throat cancer caused by human papillomavirus infections are on the rise. Once the cancer has spread within the body, the individual will typically live for only a year. Additionally, many of the available treatments work less than 20 percent of the time and have significant side effects.

The new test is done in the form of liquid biopsy. By using a method called digital droplet PCR, the test looks for DNA shed by cancer cells in the individual’s bloodstream.

The test development was led by co-first authors Catherine Haring, MD, an otolaryngology resident, and Chandan Bhambhani, PhD, a postdoctoral research fellow in the lab of senior study author Muneesh Tewari, MD, PhD.

"We can actually identify DNA from a small tumor at the back of the throat circulating throughout the entire bloodstream," Haring said in a press release.

"From a single tube of blood, this technology can isolate a single copy of tumor DNA," Bhambhani said in a press release. "And quantifying the number of copies can tell us whether a patient's cancer is responding to treatment."

The study looked at over 100 samples taken from 16 patients over the course of two years. These patients had advanced cancer that was positive for HPV 16. Seven of the patients were treated with immunotherapy regimens, while the other eleven patients underwent treatment that included chemotherapy.

"In the future, the idea is that the test would give us a window of time -- about 100 days in this example -- to find alternative therapies or a clinical trial," Swiecicki said. "And this particular patient did have significant toxicities from the therapy, some of which potentially could have been avoided once it became clear the cancer was no longer responding to the treatment."

Researchers indicated that the blood testing may also be helpful in early detection of recurrence before the cancer is incurable. Prior to treatment, patients had high levels of tumor DNA circulating in their bloodstream. In the months following their treatment, patients saw these levels drop to nearly zero. However, after six months, the levels of circulating DNA tumors in their blood began to rise again.

"Yet we weren't able to detect clinical signs of recurrence until after the two-year time point," senior study author Chad Brenner, PhD, an associate professor in the Department of Otolaryngology-Head and Neck Surgery said in a press release. "So, our test was able to detect the first signals of recurrence a year and a half before it was evident on imaging scans."

While the team is working to further optimize and validate the test, they are also teaming up with other academic medical institutions to study the relations between HPV-positive circulating tumor DNA and clinical outcomes in additional patients.