Once upon a time, cancer patients could only undergo one course of radiation treatment for their disease — and if the cancer returned, they were left with few other options.
Times have changed.
At City of Hope, patients already treated with radiotherapy for head and neck cancer may be eligible to receive radiotherapy again, through a clinical trial run by radiation oncologist Yi-Jen Chen, M.D., Ph.D.
“With the sharp-shooting we’re able to accomplish today, we can make sure to target only areas that are able to tolerate additional radiation doses,” said Chen.
Called re-irradiation, the technique depends on the body’s ability to renew and repair certain tissues rapidly, Chen explained.
Scientists recognize that some tissues in the body respond rapidly and effectively to radiation’s effects and recover quickly. These so-called early responding tissues include skin and mucous membranes. But other tissues, called late-responding tissues, feel lasting effects from radiation and heal slowly. These include bone, nerve and certain soft organ tissues.
“Every time we treat a patient with radiation, we have to respect tissue tolerance,” Chen said. “We know that tissue can only absorb a certain amount safely. We believe that in head and neck cancers, we have early responding tissues that can tolerate an additional dose.”
Chen first began exploring re-irradiation in the late 1990s while at UC Irvine, where he reported on a small series of cases using intensity modulated radiation therapy, known as IMRT. This type of therapy allows radiation oncologists to better control a varying radiation dose administered to the tumor site.
Results were good enough for physicians to continue studying re-irradiation in the head and neck, as well as selected other sites.
Today, City of Hope’s advanced TomoTherapy systems take IMRT a step further because they enable physicians to sculpt radiation doses even more precisely to tumors, allowing them to better avoid healthy-but-vulnerable structures such as the spine. That is especially critical during re-irradiation, because late-responding tissues must avoid extra radiation exposure.
The technique is an important option because oncologists need more tools to fight head and neck cancers. Besides surgery, radiation is often the first-choice treatment for this cancer, and frequently cures the disease when given as front-line therapy.
But sometimes the cancers come back. These tend to return in the same area as the original tumor — and many are in structurally difficult locations that make surgery impossible. “Only about 10 percent of these patients are even suitable for surgery,” Chen said. “And only 10 to 20 percent of patients respond to chemotherapy.”
It is no wonder that the median survival for such patients is only five to six months, he noted.
Oncologists may be able to use brachytherapy (radioactive “seeds” implanted at the site) for recurrent cancer, but that is more invasive than TomoTherapy, Chen said.
Patients in the phase I trial receive radiation therapy once a day, five times a week for up to five-and-a-half weeks. They also receive an infusion of oxaliplatin, a type of chemotherapy, every two weeks to make the cancer more sensitive to radiation’s cell-killing effects. The study includes head and neck cancer patients (except those with nasopharyngeal cancer) with squamous cell carcinoma not suitable for surgery.
Chen’s collaborating investigator on the study is Stephen Shibata, M.D., associate professor of medical oncology and director of the Gastrointestinal Cancer Program.