Greater precision makes re-irradiation an option for recurrent head and
Patients with recurrent or second primary head and neck cancer who previously received radiation therapy to the head and neck region – especially those with unresectable tumors – have typically had a dismal prognosis and limited treatment options.
Although radiation therapy offers high rates of local disease control, re-irradiating the region is usually avoided for fear of damaging previously irradiated healthy tissue, including vital structures such as the carotid arteries and neural structures. But advanced imaging and radiation therapy techniques are now being used to re-irradiate recurrent tumors while sparing nearby critical structures in patients with head and neck cancer.
For previously irradiated patients with recurrent head and neck cancer, surgery is historically considered the only potentially curative option. When these recurrent tumors are unresectable, chemotherapy provides a median survival of only 9-11 months – just a few months longer than with supportive care.
But Phan and colleagues have shown that re-irradiating recurrent tumors, if done safely, can provide local tumor control and relieve symptoms. With the goal of also prolonging patients’ survival, Phan is now leading a clinical trial that explores re-irradiation in patients with unresectable recurrent head and neck cancer.
Overcoming challenges to re-irradiation
In the 1990s, several clinical trials studied re-irradiating recurrent head and neck tumors with conventional two-dimensional and three-dimensional conformal radiation therapy. “It did improve outcomes in a select group of patients, but the side effects were pretty horrendous,” Phan says. The practice was restricted to very high risk cases.
In 2013, believing that advances in technology could improve patient safety, MD Anderson physicians began using stereotactic techniques for re-irradiation in patients with unresectable recurrent head and neck cancers. Phan and colleagues visualize these tumors by creating a composite three-dimensional image from magnetic resonance imaging, computed tomography, and positron emission tomography – computed tomography scans taken with the patient in the treatment position. The composite image is used to plan the delivery of stereotactic body radiation therapy (SBRT) with a linear accelerator or stereotactic radiosurgery with a Gamma Knife.
“We’re at a point now where we can target the tumor with stereotactic precision and avoid the nearby normal, critical tissues,” Phan says. “We previously couldn’t visualize the tumor very well. Advances in radiation therapy are very closely tied to advances in medical imaging.”
Both stereotactic modalities deliver high doses of radiation to the tumor in very few fractions – typically three to five for SBRT and one to three for radiosurgery – with minimal doses to nearby structures. The patient is re-imaged in the treatment position before each treatment session to ensure precise targeting. SBRT is used for most recurrent head and neck tumors, with stereotactic radiosurgery reserved for small skull base tumors.
Clinical benefits of re-irradiation
Patients who previously received radiation therapy to the head and neck region and receive re-irradiation for recurrent head and neck cancer at MD Anderson are enrolled in an observational study. Data from this study are showing that patients benefit from re-irradiation.
“We currently re-irradiate about 100 patients a year – an increase from about 20 patients a year prior to 2011,” Phan says. “Many folks we treated 3-5 years ago with SBRT are still alive and doing well.”
In addition to potentially prolonging survival, re-irradiation can provide symptom relief. Phan and colleagues recently analyzed the outcomes of patients who received stereotactic radiosurgery as a palliative treatment for facial pain from unresectable recurrent skull base tumors. Most patients had significantly lower self-reported pain scores 6 months after treatment. Furthermore, many patients were able to reduce their doses of pain medication, and some patients were able to discontinue their pain medications altogether.
“This was the first study to document a decrease in narcotic use after palliative-intent re-irradiation for patients with pain from recurrent head and neck cancer,” Phan says. “And in our current clinical trial, re-irradiation with SBRT is being done with the goal of long-term cancer control.”
A composite image created from magnetic resonance imaging, computed
tomography and positron emission tomography is used to plan the delivery
of stereotactic body radiation therapy. photo by Adolfo Chavez III