Patients with spinal metastases achieved greater pain relief with fewer and higher doses of stereotactic body radiation therapy (SBRT) than did a matched set of patients given conventional radiation therapy, researchers reported at the ASTRO 2020 Annual Meeting (Abstract LBA 2). A Phase II/III study in 225 patients with spinal metastases found that more than two times more individuals reported an enduring, complete reduction in pain compared to their counterparts treated with conventional radiation.
"This is the first Phase III randomized trial that has shown an improvement with dose escalation for painful spinal lesions," said lead author Arjun Sahgal, MD, Professor and Deputy Chief of Radiation Oncology at the Sunnybrook Health Sciences Centre, University of Toronto. "Patients with painful spinal metastases who meet the eligibility criteria should be offered this treatment."
Cancer can spread to any part of the body, but two-thirds of cancer patients will experience bone metastases, most often in the spine, Sahgal said.
"In fact, research has shown that 70 percent of individuals with terminal cancer will develop spinal metastases before they die. And once cancer has spread to the spine, it is rarely considered curable, although there are treatment options to help patients live longer with less pain.
Radiation therapy is the standard of care used to relieve such pain because radiation can shrink tumors and reduce inflammatory cell activity. It is delivered through multiple fractions of lower-dose, conventional radiation (CRT), or through SBRT, which allows radiation oncologists to precisely target tumors with very high doses of radiation in fewer fractions. To date, there is no definitive standard-of-care dose for radiation therapy to treat such metastases, Sahgal noted.
In the trial from the Canadian Cancer Trials Group, researchers randomized patients whose primary tumors-primarily breast, urinary tract, or lung cancers-had metastasized to painful spinal lesions. Patients were treated with either two SBRT fractions for a total dose of 24 Gy, or five CRT fractions for a total dose 20 Gy.
Subjects reported initial pain scores of greater than 2 on a scale of 1-10 (with a median score of 5). Pain scores were measured again at 3 and 6 months.
Patients in both treatment groups experienced reductions in pain. After 3 months, 35 percent of the SBRT patients in the SBRT arm reported a complete response, or no remaining pain, compared to 14 percent of those in the CRT arm. Patients continued pain free for up to 6 months, when the study concluded, with 32 percent of SBRT subjects reporting no pain versus 16 percent of those in the CRT group.
"This was not just, 'Oh, I feel a little bit better,'" said Sahgal. Patients experienced pain reduction without increasing the use of pain medications, and multivariable analyses confirmed that the type of radiation was the independent factor driving pain response, not characteristics such as the patient's age, performance status, or type of primary cancer.
"We applied a very stringent trial design to focus on the impact of radiation," said Sahgal. "It was the radiation treatment that led to the improvement."
Patient Satisfaction Greater
No difference was observed between the study arms in radiation site-specific progression-free survival or in overall survival, and after 3 months, 92 percent of SBRT patients and 86 percent of those in the CRT arm were cancer-free at the treated site. Rates at 6 months were 75 percent and 69 percent, respectively.
In terms of adverse events, both treatments were safe with respect to fractures and there was no radiation damage to the spinal cord in either group. Overall, both arms had low rates of serious adverse events and none were fatal.
Patients in the SBRT arm also reported greater satisfaction in quality-of-life measures related to financial considerations, although other quality-of-life measures did not differ between the two groups.
"Patients felt they were in a financially better position coming to the hospital and getting two treatments, rather than five," said Sahgal said. "Even though the complexity of the treatment was greater, it was better for the patient."
At the group's 2019 conference, a different group of researchers found no difference in pain reduction between patients treated for spinal metastases with SBRT and those treated with conventional radiation. In the new study, patients received a higher dose of radiation, an SBRT dose of 24 Gy in two fractions, compared to the earlier trial's dose of 16/18 Gy in a single fraction.
Sahgal said he was motivated to conduct this research out of frustration over the years with being unable to adequately relieve the suffering of patients with advanced stage cancer.
"We saw we were getting improvements in pain, but our patients were not pain-free. With the development of SBRT, and spinal SBRT in particular, we started to wonder if we could do better. With these new research results, we think we can."
Kurt Samson is a contributing writer.