High-dose radiation therapy may stall tumor growth in patients with advanced lung cancer who are not fully responding to drug therapies, a preliminary study suggests.
The study involved patients whose lung cancer was considered "oligoprogressive."
That means the cancer had spread to other sites in the body, and the patients were having a mixed response to standard systemic treatments -- including targeted drugs, immune system therapies and chemotherapy.
Essentially, the treatments were successfully suppressing growth in some of those distant tumors, but not others.
In the trial, the researchers found that applying high-dose radiation to those drug-resistant sites extended patients' progression-free survival -- the amount of time they remained stable.
Overall, patients who received radiation showed no cancer progression for a median of 44 weeks -- which means half remained progression-free longer, and half for a shorter period.
That was nearly five times longer than the median for patients given standard care, at 9 weeks.
The findings suggest the radiation technique may give these patients "more mileage" out of their systemic drug therapies, said lead researcher Dr. C. Jillian Tsai, a radiation oncologist at Memorial Sloan Kettering Cancer Center in New York City.
Doctors have been occasionally using the approach in practice, on a case-by-case basis, according to Tsai.
Sometimes a patient is doing well on systemic therapy but just a few lesions are no longer responding to the treatment, so doctors may try targeted radiation therapy to control those growths.
Until recently, though, the tactic had not been tested in clinical trials. Three such studies are now ongoing, Tsai said.
More evidence is needed before the approach can become the standard of care, said Dr. Steven Chmura, a radiation oncologist at the University of Chicago who was not involved in the research.
"This is the first study to test this approach formally, asking if we can extend the use of a systemic agent when it's working well in most of the body and only failing in a few spots," Chmura said.
"A phase 3 trial is needed to really change the standard of care and clinical guidelines," he said, referring to the final phase in clinical testing of a new therapy.
Tsai presented the findings Sunday at the annual meeting of the American Society for Radiation Oncology in Chicago. Studies presented at meetings are generally considered preliminary until they are published in a peer-reviewed journal.
The trial involved 58 patients with metastatic lung cancer and 44 with metastatic breast cancer. Metastatic means the initial cancer had spread to other sites in the body. All patients had one to five lesions that were progressing despite systemic therapy.
Tsai's team randomly assigned the patients to have either stereotactic body radiation therapy, also called SBRT, or standard care. SBRT is a widely used technique designed to deliver precise, high doses of radiation to the cancer site and spare surrounding tissue, Tsai explained.
While lung cancer patients who received SBRT remained progression-free for a median of 44 weeks, compared to 9 weeks for those who did not undergo radiation, no such benefit was seen in breast cancer patients.
"It may be because of the different biology of the diseases," Tsai said. She noted that in breast cancer patients, the lesions treated with radiation did respond -- but new ones developed.
More research is needed to fully understand the different results for breast cancer patients, Tsai said. She said her team also wants to figure out which characteristics make individual patients more likely to respond to the radiation therapy.
As for potential side effects of SBRT, they vary depending on where the radiation is given. If it's delivered to the bones, for example, it can cause a temporary pain flare-up, Tsai said. If the radiation is to the lungs, it can cause inflammation.
During the trial, eight patients given radiation had at least a moderately severe side effect.
While phase 3 trials have not been done yet, it is possible for lung cancer patients like those in this study to get radiation therapy.
Chmura said, "I think if a patient with [lung cancer] is doing well on systemic therapy but is told they are progressing in a few small spots, it would be useful for them to know this treatment option exists."
SBRT has been used for about a decade, he noted, and is widely available around the world.