Tumor Dose Response in Yttrium-90 Resin Microsphere Embolization for Neuroendocrine Liver Metastases: A Tumor-Specific Analysis with Dose Estimation Using SPECT-CT.

PURPOSE: To evaluate dose-response relationship in yttrium-90 (90Y) resin microsphere radioembolization for neuroendocrine tumor (NET) liver metastases using a tumor-specific dose estimation based on technetium-99m-labeled macroaggregated albumin (99mTc MAA) single photon emission computed tomography (SPECT)-CT. MATERIALS AND METHODS: Fifty-five tumors (mean size 3.9 cm) in 15 patients (10 women; mean age 57 y) were evaluated. Tumor-specific absorbed dose was estimated using a partition model. Initial (median 2.3 months) follow-up data were available for all tumors; last (median 7.6 months) follow-up data were available for 45 tumors. Tumor response was evaluated using Modified Response Evaluation Criteria in Solid Tumors (mRECIST) on follow-up CT. Tumors with complete or partial response were considered responders. Mean tumor absorbed dose was 231.4 Gy ± 184.3, and mean nontumor liver absorbed dose was 39.0 Gy ± 18.0. RESULTS: Thirty-six (65.5%) and 30 (66.7%) tumors showed response at initial and last follow-up, respectively. Mean absorbed doses in responders and nonresponders at initial and last follow-up were 285.8 Gy ± 191.1 and 128.1 Gy ± 117.1 (P = .0004) and 314.3 Gy ± 195.8 and 115.7 Gy ± 117.4 (P = .0001). Cutoff value of ≥ 191.3 Gy for tumor-specific absorbed dose predicted tumor response with 93% specificity, whereas < 72.8 Gy predicted nonresponse with 100% specificity at last follow-up. Estimated mean absorbed tumor dose per patient was significantly higher in responders versus nonresponders over the follow-up period (224.5 Gy ± 90.3 vs 70.0 Gy ± 28.0; P = .007). CONCLUSIONS: Tumor-specific absorbed dose, estimated with a partition model, was significantly associated with tumor response in NET liver metastases. An estimated dose ≥ 191.3 Gy predicted treatment response with high sensitivity and specificity.

Radiation-induced liver disease as a mimic of liver metastases at serial PET/CT during neoadjuvant chemoradiation of distal esophageal cancer.

PURPOSE: To determine the frequency and appearance of radiation-induced liver disease on PET/CT in patients undergoing serial imaging during neoadjuvant chemoradiation of distal esophageal cancer. MATERIALS AND METHODS: In this IRB-approved, HIPAA-compliant retrospective analysis, we identified 112 patients with distal esophageal cancer treated by neoadjuvant chemoradiation who had serial PET/CT imaging available for review. Two readers reviewed all studies in consensus and recorded those cases where new foci of visually detectable increased FDG avidity appeared in the liver during therapy. The etiology of such foci was determined from corresponding findings at CT or MRI, by hepatic biopsy during surgery, by characteristic evolution on post-operative imaging, or by a combination of these methods. RESULTS: New foci of FDG avidity developed in the liver during neoadjuvant therapy in 10 of 112 (9%) patients, of whom nine (8%) were determined to have radiation-induced liver disease based on further imaging and/or biopsy and one of whom had developed interval metastatic disease based on biopsy. In the cases of radiation-induced liver disease, the abnormal foci were found only in the caudate and left hepatic lobes, near the primary tumor, while the patient who developed interval metastatic disease had involvement of the inferior right hepatic lobe, remote from the radiation therapy field. CONCLUSION: New foci of increased FDG avidity are commonly seen in the caudate and left hepatic lobes of the liver during neoadjuvant chemoradiation of distal esophageal cancer, and these findings generally reflect radiation-induced liver disease rather than metastatic disease.

Relationship between elevated serum troponin values in end-stage renal disease patients and abnormal isotopic cardiac scans following stress.

One hundred asymptomatic high-risk renal transplant candidates were screened for asymptomatic coronary artery disease using stress cardiac isotopic imaging. The cardiac markers, serum cTnT, cTnI, and CKMB, were collected pre and post stress testing. Of the 99 patients whose cardiac scans were technically satisfactory, 32 were normal, 49 had a definite imaging abnormality and the scan was indeterminate in the remaining 18 patients. Based on these results, patients were stratified into either normal, indeterminate or abnormal scan groups. They then were analyzed to detect any correlations between cardiac perfusion defects and either elevated pre-stress cardiac markers or consistent changes 24h after stress testing. While the mean pre-stress serum values for both cardiac troponin T (0.117 +/- 0.12 microgram/L) and cardiac troponin I (0.235 +/- 0.89 microgram/L) were increased in the abnormal cardiac scan group, only the cTnT value proved to differ significantly from the normal group (p < 0.01). For the indeterminate group neither marker was different from the normal scan group. Only an elevated serum cTnT > 0.1 microgram/L (OR 3.042, p = 0.030) proved to discriminate an abnormal scan in this population. It is concluded that the increase in pre-stress serum cTnT encountered in patients with chronic renal failure, with or without evidence of overt, symptomatic coronary artery disease, may represent a combination of subclinical myocardial damage and a prolonged half-life of the marker in the serum. Because of the frequency of elevated serum concentrations of cTnT and, to a lesser degree cTnI, the physician should exercise caution when interpreting a single elevated Troponin value during the evaluation of chest pain in patients with end-stage renal disease. A cTnT > 0.1 microgram/L increases the likelihood of finding significant coronary artery disease three fold in high-risk ESRD patients being evaluated for renal transplantation.