CHICAGO—Stereotactic body radiation therapy should now be considered a standard treatment for patients with inoperable early-stage lung cancer, according to researchers who found that the technique was associated with a 98% rate of local control in such patients at three years.
Speaking here at the American Society for Radiation Oncology (ASTRO) Annual Meeting, lead author Robert D. Timmerman, MD, said, “Stereotactic body radiation therapy is strikingly better than conventional radiotherapy.”
Based on historical data, “one would expect a local control rate of only 30% to 50% for patients with inoperable lung cancer treated with conventional radiotherapy,” said Dr. Timmerman, the Effie Marie Cain Distinguished Chair in Cancer Therapy Research and Professor of Radiation Oncology at the University of Texas Southwestern Medical Center in Dallas.
Comorbidities Preclude Surgery
Dr. Timmerman presented the results of the 55-patient, Phase II Radiation Therapy Oncology Group 0236 study, the first North American cooperative group trial to use stereotactic body radiation therapy.
The patients, who were enrolled from May 2004 to October 2006, had to have Stage T1 or T2 lung cancer with a primary tumor mass of 5 cm or less, or a Stage T3 tumor in the chest wall of 5 cm or less.
All patients also had comorbidities, such as emphysema, cancer, heart disease, or diabetes, that disqualified them from surgery.
Radiation therapy consisted of three 20 Gy fractions, for a total dose of 60 Gy, delivered over the course of one week. After correction for tissue heterogeneity, patients received an actual total dose of 54 Gy.
At a median follow-up of 48.1 months, only one of the 55 patients suffered a failure in local control, defined as an increase in lesion size of at least 20% on CT, followed by either a confirmatory biopsy or PET scan.
The three-year disease-free survival rate was 48%, and the overall survival rate was 56%. This compares favorably with the 30% to 50% three-year survival rate associated with conventional radiation, Dr. Timmerman said.
Eighteen percent of the patients died of metastatic lung cancer, but there were no treatment-related deaths.
Grade 3 and 4 adverse events occurred in seven (13%) and two (4%) patients, respectively. The most common severe adverse events were pulmonary/upper respiratory and musculoskeletal.
1 Week vs 6–7 Weeks of Treatments
In addition to its efficacy, an advantage of stereotactic radiation is that treatment takes place in three sessions over one week, compared with the six or seven weeks of sessions required of conventional radiation, he said.
“This is probably the first significant change in these patients in 50 years,” Dr. Timmerman said.
Past ASTRO Program Chair Stephen M. Hahn, MD, Chairman of Radiation Oncology at the University of Pennsylvania School of Medicine, said he agrees the findings are practice-changing.
Patients with inoperable lung cancer do poorly precisely because they cannot undergo surgery, he explained. “This approach gives us a high chance of controlling their cancer.
“Sometimes a Phase II trial is so outstanding that doing a Phase III trial [becomes problematic]. It would be an ethical dilemma to treat these patients with conventional radiation and not offer them stereotactic radiation,” he said.
Nevertheless, Dr. Timmerman said a trial comparing stereotactic with conventional radiation is under way in Scandinavia and another is planned in Australia.
Cautions from ASTRO President
ASTRO 2009–2010 President Anthony L. Zietman, MD, the Jenot W. and William U. Shipley Professor of Radiation Oncology at Harvard Medical School, was less enthusiastic.
“This technique has been aggressively pushed by manufacturers, and it has established itself as an effective way to treat brain metastases. What about other cancers? In my view, most lung tumors are not suited for this treatment, which is best for smaller peripheral lung cancers,” he said.
Dr. Timmerman agreed the technique will not “unseat” surgery for operable lung cancers—“It is for medically frail patients,” he said, estimating that of the approximately 215,000 cases of lung cancer in the US each year, about 25% are Stage 1, and about 20% of that group have inoperable disease.
Cancer centers often call the treatments by the brand names of the manufacturers, including Axesse, CyberKnife, Gamma Knife, Novalis, Primatom, Synergy, X-Knife, TomoTherapy, and Trilogy, according to a statement from ASTRO.
Obesity Risk Factor for Pain
In a second study presented at the meeting, researchers reported that obesity was the number-one predictor of whether early-stage lung cancer patients would develop chest wall pain after stereotactic body radiation therapy.
The retrospective study involved 256 patients with tumors within 2.5 cm of the chest wall that had been treated with stereotactic body radiation therapy between August 2004 and August 2008.
Overall, 39% of patients developed skin toxicity, 6% developed acute pain, and 22% developed chronic pain.
Patients who received a high radiation dose of 35 Gy had an elevated risk for skin reactions and pain, compared with those who received a lower dose.
“But to our surprise, obesity was an even greater predictor of adverse reactions,” said lead author James Welsh, MD, Assistant Professor in the Department of Radiation Oncology at the University of Texas M. D. Anderson Cancer Center.
Specifically, obese patients were more than twice as likely to develop chronic pain compared with those of normal body weight, he said. Obese patients who were diabetic were over three times more likely to develop chest wall pain, compared with patients who do not have diabetes, he added.
“For the most part, this treatment is well tolerated. This study points us to steps we can take to further reduce the risk of side effects”