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Noting that pelvic coverage can increase radiation dosing for liver computed tomography (CT) by 29 to 39 percent, researchers found low three-year cumulative rates of incidental pelvic tumors and isolated pelvic metastasis in follow-up liver CT imaging of over 1,100 people treated for hepatocellular carcinoma.
For people treated for hepatocellular carcinoma (HCC), do the findings from pelvic coverage in follow-up liver computed tomography (CT) warrant the risk of increased radiation dosing?
In an attempt to answer that question, researchers performed a retrospective study of 1,122 patients (mean age of 60) treated for HCC and assessed rates of extrahepatic metastasis, isolated pelvic metastasis, and incidental pelvic tumor on follow-up CT imaging. According to the study, recently published in Radiology, the median follow-up periods were 3.7 years for isolated pelvic metastasis and incidental pelvic tumors, and 3.8 years for extrahepatic metastasis. The researchers noted a median of 10 follow-up CT examinations for patients during this time period.
The researchers found three-year cumulative rates of 1.4 percent for isolated pelvic metastasis and 0.5 percent for incidental pelvic tumor. The inclusion of pelvic coverage on follow-up liver CT examinations increased radiation dosing by 29 percent on contrast-enhanced CT and 39 percent on CT scans without contrast enhancement, according to the study authors.
“Although little is known about the effect of radiation from CT in patients with cancer, reducing radiation dose would be meaningful in the ‘as low as reasonably achievable’ principle,” wrote Kyoung Doo Song, M.D., who is affiliated with the Department of Radiology at the Samsung Medical Center at Sungkyunkwan University in Seoul, Korea, and colleagues. “The number of images requiring interpretation affects the time, cost, and burden of reading images. … In this context, excluding the pelvic scan in relevant patients may decrease the workload and allow the radiologists to focus on evaluating more pertinent sites.”
(Editor’s note: For related content, see “Abbreviated MRI and Early-Stage Hepatocellular Carcinoma: What a New Multicenter Study Reveals” and “Study Says Machine Learning MRI Model May Help Predict Recurrence Risk of Hepatocellular Carcinoma.”)
For extrahepatic metastasis, the researchers noted cumulative one-year, two-year and three-year rates of 8.3 percent, 11.8 percent, and 14.4 percent, respectively. Out of the 169 patients in the cohort who had extrahepatic metastasis, Song and colleagues found the most common locations were lung (52 patients), lymph node (39 patients) and peritoneum (36 patients). The study authors added that only 15 of the 25 patients with extrahepatic metastasis had isolated pelvic metastasis.
According to the study, baseline risk factors for an increased risk of extrahepatic metastasis included size of the largest tumor with the researchers noting a 1.8 hazard ratio (HR) for tumors greater than 5 cm in comparison to tumors less than or equal to 3 cm. Song and colleagues also noted HRs of 2.0, 2.7 and 4.2 for T2, T3 and T4 staging, respectively, in comparison to T1 staging.
Acknowledging the inherent limitations of a single center retrospective study, the authors acknowledged that some patients may not have had enough follow-up examinations and there may be variation with cumulative rates of pelvic metastasis and extrahepatic metastasis at different institutions. Song and colleagues also noted the study’s statistical power may have been insufficient to assess associated factors with isolated pelvic metastasis due to a low incidence of the condition in the study cohort.