CHICAGO – Lower-dose radiation therapy may be safe for some patients with human papillomavirus (HPV)-positive oropharyngeal cancer, decreasing the risk of often long-term side effects, such as trouble swallowing, dry mouth, loss of taste, neck stiffness, and thyroid problems, investigators reported at the annual meeting of the American Society of Clinical Oncology.
Two-year overall survival and progression-free survival were 93% and 80%, respectively, among 62 patients with operable stage III/IVA HPV-positive oropharyngeal squamous carcinoma who received lower-dose intensity-modulated radiation therapy (IMRT) after clinical complete response to induction chemotherapy, reported Dr. Anthony Cmelak, professor of radiation oncology at Vanderbilt University, Nashville, Tenn., and medical director of the Vanderbilt-Ingram Cancer Center at Franklin.
Laura Nikolaides/Frontline Medical News
Dr. Anthony Cmelak
Overall, the phase II study enrolled 90 patients, median age 57 years, who all received induction chemotherapy with paclitaxel, cisplatin, and cetuximab. The response to induction chemotherapy determined IMRT dose. The 62 patients who had a complete clinical response received a reduced dose (54 Gy) of IMRT, and the rest of the patients received standard dose IMRT (70 Gy). All patients received standard cetuximab along with radiation.
Two-year overall survival and progression-free survival for the higher-risk patients who received the standard dose of IMRT were 87% and 65% respectively. Among those patients receiving low-dose IMRT, survival was slightly higher for those with less than 10 pack-years of smoking and earlier-stage disease; in those patients 2-year progression-free and overall survival were 92% and 97%, respectively.
However, Dr. Cmelak does not yet recommend modifying regimens for patients with HPV-positive disease. "I don’t recommend using lower doses now, off study. Ultimately, we will need a large randomized trial," he said. "This study represents one more piece of evidence that we need to look at the optimal regimen for both chemotherapy and radiation technique and dosage to minimize toxicities," he added.
"We are not at the point where we know exactly how to treat patients with HPV-positive cancers. What we do know now is that there is a different biology to their tumors," commented Dr. Gregory A. Masters, of the Helen F. Graham Cancer Center, Newark, Del., who attended the briefing but was not involved with the study. However, the study represents progress toward precision medicine, he said. "Most of what we have been doing over the last 49 years in oncology is escalating dosages. This is not necessarily always the right answer," he added.
The research was supported by the National Institutes of Health. Dr. Cmelak reported a consultancy role and honoraria from Bristol-Myers Squibb. Dr. Masters reported no disclosures.
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