How Often Should Patients Receive Imaging After Spine SBRT?

TOPLINE:

A new study suggests individualized MRI surveillance of the spine based on patients’ risk for progression after spine stereotactic body radiotherapy (SBRT) can optimize the detection of disease progression.

METHODOLOGY:

• Clear guidance on the frequency of follow-up MRIs after SBRT for spine metastases is lacking. This study aims to develop more accurate surveillance strategies to improve patient outcomes and reduce unnecessary burdens on both patients and the healthcare system.
• Researchers reviewed data from patients who received SBRT for spine metastases between July 2008 and March 2021 and who had at least two follow-up spine MRIs.
• The primary outcome was the cumulative incidence of spine progression, defined as either local progression at the radiated site or the development of new metastasis within the nonradiated spine on follow-up MRIs.
• They also categorized the patients using Recursive Partitioning Analysis for progression and came up with the best follow-up interval for each category.
• The median interval between follow-up MRIs at any point during follow-up was 3.4 months — 3.2 months within the initial 2 years after SBRT and 3.9 months thereafter.

TAKEAWAY:

• The cumulative incidence of spine progression was 19.2% at 1 year, 26.7% at 2 years, 32.8% at 3 years, and 35.3% at 4 years.
• The researchers identified three key variables (epidural disease, paraspinal disease, and stable/unstable Spinal Instability Neoplastic Score category) to categorize patients into low-risk (4-year risk for progression, 23.4%), intermediate-risk (39%), and high-risk (51.8%) groups.
• For the high-risk group, the rate of spine progression was higher during the initial 13.2 months after SBRT, decreasing significantly thereafter (P
• The follow-up frequencies varied according to the expected probability of detecting progression per scan for each risk category. Low-risk patients with a 3.75% probability needed imaging every 6 months, intermediate-risk every 3.1 months, and high-risk every month for 13.2 months, then every 4.4 months. For a 5% probability, high-risk cases required imaging every 1.3 months initially for the first 13.2 months after SBRT and every 5.9 months afterward.

IN PRACTICE:

“In addition to providing guidance in choosing the appropriate surveillance strategy post-SBRT, we believe that the risk stratification model presented in this study can also be used prior to treatment to aid in the clinical decision-making process for the planned course of spine SBRT and potentially for patient counselling,” the authors concluded.

SOURCE:

This study was led by Hanbo Chen from Odette Cancer Centre University of Toronto, Toronto, Ontario, Canada, and published online in the International Journal of Radiation Oncology, Biology, Physics.

LIMITATIONS:

The study did not explicitly consider the interdependence among vertebral segments from the same patient. The impact of systemic therapy was not taken into consideration. Also, the findings were applicable solely to patients without symptomatic progression. Moreover, this study was conducted at a single center.

DISCLOSURES:

This study did not receive any funding. Two authors disclosed financial ties outside this work. Other authors did not report any conflict of interests.