The Precision of Hepatic Arterial Infusion Scintigraphy as a Quantitative Biomarker of Tumor Microvasculature.

OBJECTIVE: Optimal clinical development of new cancer therapies targeting tumor vasculature requires new target-specific response assays. This clinical study examined the test-retest repeatability of SPECT as an in vivo assay of angiogenic hepatic tumor microvasculature using an intraarterial infusion of 99m Tc-macroaggregated albumin (MAA) delivered via a hepatic artery infusion (HAI) pump.

MATERIALS AND METHODS: Patients with primary or secondary cancerous liver tumors with HAI pump-catheter implants placed for HAI chemotherapy underwent hepatic SPECT after separate arterial infusions of 37 and 185 MBq of 99m Tc-MAA via an HAI pump. Quantitative measures of hepatic tumor MAA uptake were obtained from paired test-retest SPECT datasets. Repeatability was defined by quotients of paired measurands with 95% CIs and coefficients of repeatability (CRs).

RESULTS: Test-retest HAI pump SPECT yielded highly repeatable measurements in quantitative indexes of tumor microvasculature. Variability in repeat test-retest measurements was small relative to the range of observed measurements between different tumors. The total hepatic tumor microvascular MAA accumulation (percentage injected dose) proved most repeatable, with test-retest value quotients near unity (quotients: median, 1.10 ± 0.09 [SD]; range, 1.03-1.32; 95% CI, 1.07-1.19) and 1.6% CR. Tumor MAA uptake values ranged from 5% to 18% injected dose.

CONCLUSION: This article describes the precision of HAI SPECT as a quantitative biomarker of tumor microvasculature under conditions of repeatability. The results support clinical testing of HAI SPECT as a radiologic response biomarker for angiotropic tumor therapy.