Though it’s common practice, imaging hepatocellular carcinoma (HCC) patients one month after selective internal radiation therapy (SIRT) rarely changes case management, a team from Minneapolis, Minnesota, reported in Diagnostic and Interventional Imaging this month.
Selective internal radiation therapy has been around for about two decades, corresponding author Shamar Young, MD, and colleagues said, and since has been employed to treat countless primary and secondary tumors. But, despite its utility to liver cancer patients, early imaging findings from SIRT studies are typically difficult to interpret.
“The mechanism of treatment for SIRT is different than other locoregional therapies of the liver,” Young, an assistant professor in the Department of Radiology at the University of Minnesota, and co-authors wrote. “Unlike transarterial chemoembolization (TACE) and ablation, SIRT induces tumor death via intra-arterial beta radiation.”
While tumor responses to TACE and ablation therapies can be reliably calculated with imaging around the one-month mark, SIRT results are more difficult to read, meaning physicians have to wait around three months before they can ensure an accurate response determination, they said. A recent survey from the Society of Interventional Radiology found just 35 percent of radiologists preferred the first round of imaging after treatment to be at one month; 43 percent preferred to wait three months.
“Because tumor response cannot be reliably determined at one month, the only remaining reason to image at this time point is if it will affect the treatment course,” Young et al. wrote. “This raises the question as to whether there is any clinical utility of imaging SIRT patients at one month.”
The researchers evaluated 85 patients around 60 years old during a four-year period for their study. The patients, who were a majority men, underwent a total of 109 SIRT treatments for either primary or secondary hepatic malignancies, and Young’s team tracked one-month post-treatment imaging findings for each participant.
The findings were significant enough to trigger management changes in 9.2 percent of cases, the authors wrote, but not all results were statistically significant.
“An imaging study which significantly alters management in nearly 1 out of 10 patients would arguably be of meaningful value,” Young and co-authors said. “However, when the treatment groups were divided into HCC and non-HCC cohorts, imaging was found to be clinically significant in two of 61 HCC treatments and eight of 48 non-HCC treatments.”
That suggests patients with HCC are highly unlikely to benefit from 30-day imaging, they wrote, while non-HCC patients might see more good come from it.
Young and colleagues said even physicians attempting to push up post-SIRT imaging to one month in an attempt to detect treatment complications won’t see much benefit from the early bird approach. The most common adverse events after SIRT are increases in hepatic-related laboratory markers and abdominal pain—both conditions that are managed conservatively, without any need for imaging.
“In this study, patients who undergo treatment of HCC with SIRT rarely gain clinically relevant data from their one-month post-treatment imaging, suggesting it is not warranted,” the authors wrote. “Conversely, those with non-HCC disease are significantly more likely to gain clinically relevant information from one month post-treatment imaging, and it is likely warranted in this population.”