Cleveland Clinic Researchers Develop New Tool for Spine Radiosurgery Decision-Making

By analyzing clinical variables and outcomes from 444 patients who underwent spine radiosurgery (SRS) for metastases, Cleveland Clinic researchers have developed a new prognostic index that should help identify patients most likely to benefit from this treatment. The analysis found significant variability in survival after SRS and identified several key factors that were predictive of better overall survival.

Cleveland Clinic Cancer Center radiation oncologist Samuel Chao, MD, presented the team’s findings at the 2016 annual meeting of the American Society for Radiation Oncology (ASTRO) in Boston.

SRS: An effective but resource-intensive treatment

Spinal metastasis is common in many cancers. Targeted therapies have extended patients’ survival, increasing the need for improved tumor control and effective, durable palliation for patients with spine metastases, especially those with limited metastatic burden.

In the last decade, SRS has emerged as an important treatment modality for primary spine tumors and spinal metastases. “Spine radiosurgery is extremely effective in providing local control as well as palliation of pain and neurologic symptoms in a wide variety of patients, in a single radiotherapy session,” says Ehsan Balagamwala, MD, a resident physician at Cleveland Clinic Cancer Center and a member of the research team.

However, SRS requires a significant amount of dedicated resources and involves a lengthier, more elaborate treatment planning process than conventional radiotherapy. Appropriate patient selection is important to ensure that SRS is properly utilized. The Cleveland Clinic researchers sought to create a prognostic index to improve clinicians’ selection of SRS patients.

Risk stratification in patients with spine metastases

The researchers performed a recursive partitioning analysis (RPA) of all patients treated with SRS at Cleveland Clinic (2006-2015) to identify clinical characteristics that would predict overall survival (OS) and allow patients to be classified into distinct risk groups.

Their analysis showed that Karnofsky Performance Status (KPS), systemic disease status, visceral metastasis and age were the most important prognostic factors. KPS > 70, controlled systemic disease, single-level spinal disease, absence of visceral metastases and time from primary diagnosis were predictive of better OS.

RPA yielded three distinct patient classes with differing survival statistics:

The case for conventional radiotherapy for Class 3 patients

For patients in Class 1 or 2, Dr. Balagamwala says the analysis shows that SRS can be utilized either in the upfront setting or as salvage after conventional radiotherapy.

The treatment choice for Class 3 patients is more challenging. “Patients in Class 3 have significantly worse survival compared to Class 1 and 2 patients, and as a result may be better candidates for conventional radiotherapy,” Dr. Balagamwala says. “If Class 3 patients have not received in-field spine radiotherapy, then conventional radiotherapy is likely the best option. If they have received prior radiotherapy, then a multidisciplinary discussion between the radiation and medical oncologist as well as neurosurgeon is warranted to select the best treatment option.”

SRS can be demanding for patients, as it is more time-intensive than conventional radiotherapy at each stage, Dr. Balagamwala says. The simulation process for SRS can last as long as one hour, compared to 20 minutes for conventional radiotherapy. Similarly, the treatment itself can last 30 to 40 minutes, compared to five to 10 minutes for conventional radiotherapy. SRS treatment planning takes approximately seven days (although it can be expedited to four or five days if necessary), while conventional radiotherapy can be started the same day as simulation in urgent/emergent cases. Cleveland Clinic Cancer Center’s Department of Radiation Oncology is also working to decrease the time from simulation to treatment for spine stereotactic body radiotherapy.

When recommending a particular radiation treatment for an individual patient, a physician must take these technical details into account, Dr. Balagamwala says. For instance, a patient in Class 3 might be in significant pain and unable to tolerate SRS’ longer simulation and treatment times. That patient may also require rapid initiation of radiotherapy, which would be difficult to achieve with SRS and therefore may be better suited for conventional radiotherapy.

Although this study is the largest spine radiotherapy RPA reported to date, Dr. Balagamwala says it will be important to independently verify the results. The research team is initiating collaboration with several institutions to conduct validation studies, he says.