The Predictive Value of SPECT/CT imaging in colorectal liver metastases response after 90Y-radioembolization

Abstract

The aim of this study was to evaluate a modified method of calculating the 99mTc/90Y tumor-to-normal-liver uptake ratio (mT/N) based on SPECT/CT imaging, for use in predicting the overall response of colorectal liver tumors after radioembolization. A modified phantom-based method of tumor-to-normal-liver ratio calculation was proposed and assessed. In contrast to the traditional method based on data gathered from the whole tumor, gamma counts are collected only from a 2D region of interest delineated in the SPECT/CT section with the longest tumor diameter (as specified in RECIST 1.1). The modified tumor-to-normal-liver ratio (mT/N1) and 90Y predicted tumor absorbed dose (PAD) were obtained based on 99mTc-MAA SPECT/CT, and similarly the modified tumor-to-normal-liver ratio (mT/N2) and 90Y actual tumor absorbed dose (AAD) were calculated after 90Y-SPECT/CT. Tumor response was assessed on follow-up CTs. Using the newly proposed method, a total of 103 liver colorectal metastases in 21 patients who underwent radioembolization (between June 2009 and October 2015) were evaluated in pre-treatment CT scans and 99mTc-MAA-SPECT/CT scans and compared with post-treatment 90Y-SPECT/CT scans and follow-up CT scans. The results showed that the mT/N1 ratio (p = 0.012), PAD (p < 0.001) and AAD (p < 0.001) were predictors of tumor response after radioembolization. The time to progression was significantly lengthened for tumors with mT/N1 higher than 1.7 or PAD higher than 70 Gy. The risk of progression for tumors with mT/N1 lower than 1.7 or PAD below 70 Gy was significantly higher. The mT/N2 ratio had no significant correlation with treatment results.ConclusionThe mT/N1 ratio, PAD, and AAD can be used as predictors of tumor response to SIRT treatment, and SPECT/CT imaging can be used for dosimetric assessment of radioembolization.

Quantitative Imaging Biomarkers for 90Y Distribution on Bremsstrahlung SPECT After Resin-Based Radioembolization

“…Previous studies have shown the feasibility and value of quantitative SPECT for the evaluation of the extra-and intrahepatic distribution of 90 Y and absorbed dose quantifications after TARE (19). More recently, several studies investigating hepatic metastases found CT perfusion imaging and metabolic response assessment using PET predictive of tumor response early after TARE (20).…”

Regorafenib Prior to Selective Internal Radiation Therapy Using 90Y-Resin Microspheres for Refractory Metastatic Colorectal Cancer Liver Metastases: Analysis of Safety, Dosimetry, and Molecular Markers

“…One study noted a strong statistically significant dose-effect of resin Y90 microspheres with improved hepatic tumor PFS and OS, with mean tumor dose of 51 Gy (± 28 Gy), range 7–174 Gy (15). In a prospective study of 21 mCRC patients receiving resin Y90 SIRT employing SPECT/CT for post-SIRT dosimetry, the tumor/normal ratio of absorbed dose was significantly ( p < 0.001) associated with radiographic response (RECIST 1.1), longer PFS and OS in those patients with a T/N ratio of at least 1.7 or tumor dose of 70 Gy (14). Our patients generally received a lower mean tumor dose of Y90 than these studies which might be a factor in the comparatively lower response rate.…”

Yttrium-90 TOF-PET-Based EUD Predicts Response Post Liver Radioembolizations Using Recommended Manufacturer FDG Reconstruction Parameters

“…Thus, the absorbed dose D in each whole sector region, i.e. including rods and plastic, is given by the relation ( 6 ):…”