TheraSphere® For Treatment of Metastases in Liver

Feasibility of a Personalized Dosimetry-based Treatment Planning for Radioembolization in the Treatment of Unresectable Colorectal Metastases in Liver

To investigate whether the dose predicted by pre-therapy 99mTc MAA SPECT predicts the dose to the liver from the 90Y microspheres as assessed by post-therapy 90Y SPECT/CT or positron emission tomography (PET)/CT.

This study will acquire imaging information from 3-5 patients that will demonstrate feasibility of future implementation of personal dosimetry-based treatment planning for Trans-arterial Radio-embolization (TARE). TARE therapy of liver neoplasia using 90Y-theraspheres has a long history. The device is FDA approved for the treatment of hepatocellular carcinoma, but has been used extensively for treatment of secondary liver neoplasia, including metastatic colorectal lesions under Humanitarian Device Exemption protocols such as this one. As a targeted radioactive therapy, the current TARE implementation suffers from a lack of efficiency characteristic of radiopharmaceutical therapy (RPT) in general; namely, that the activity determined to treat the patient is not optimized according to normal organ tolerated absorbed dose and tumor efficacy thresholds. The amount of activity to be administered is determined from volumetrics established from associated imaging, either MRI or X-ray CT, where the total volume of irradiated tissue is considered as irrigated by the artery selected for administration, including both tumor and normal organ tissue. From this volume determination, the activity necessary to deliver an average pre-determined safe absorbed dose (120 Gy) to the entire irradiated region is calculated and administered. In RPT, in the theranostic paradigm, a pre-therapeutic, or surrogate, quantity of activity is administered to the patient; 3D imaging (SPECT/CT or PET/CT) is then acquired at several time points and the individual patient's pharmacokinetics are determined, the normal organ and tumor dosimetry are performed and the optimal administered activity calculated that will deliver safe and efficacious treatment for the individual patient is determined, generally limited by the normal organ at risk maximum tolerated dose. TARE presents a number of unique characteristics that enable a simpler version of this approach than is typical for most RPT. The method of administration means that only the normal liver and lungs need to be considered as potential organs at risk as the microspheres embolize and do not circulate systemically; the lack of associated photons in the 90Y decay chain means that a simple activity-to-dose-rate conversion can be used; the embolization means that only a single imaging time point is necessary as there is no redistribution of activity over time and the dose rate is converted to absorbed dose using the physical decay parameters of 90Y. These natural simplifications are already exploited in the current volumetric paradigm, where a 99mTc-macro albumin aggregate (MAA) surrogate and planar imaging are used to determine the fraction of total activity that is shunted to the lung and where a derived conversion factor is used to convert activity to absorbed dose. The technical complication in TARE is that the surrogate (99mTc-MAA) has a different nature from the therapeutic device (90Y-theraspheres), and thus the reliability of the predictive quality of the surrogate is disputed. However, with precise and advanced imaging reconstruction and dosimetry the investigators have shown the ability to accurately and precisely predict normal liver and tumor average 90Y-therasphere uptake and absorbed dose from 99mTc-MAA. This protocol seeks to acquire the imaging information from 3-5 patients that will demonstrate feasibility of future implementation of personal dosimetry-based treatment planning for TARE. In addition to the clinical standard of care assessments: 1. a single SPECT/CT instead of the current planar image will be acquired of the surrogate 99mTc-MAA; 2. An additional single 3D image (either SPECT/CT or PET/CT, depending on machine availability) will be acquired up to 6 hours post-administration of the therapeutic 90Y-microspheres for comparison. Informed consent will be obtained.

To investigate whether the dose predicted by pre-therapy 99mTc MAA SPECT predicts the dose to the liver from the 90Y microspheres as assessed by post-therapy 90Y SPECT/CT or PET/CT.

TheraSphere is a radiotherapy treatment for primary and secondary liver neoplasia. This is an imaging study that will examine 3-5 patients who have been treated for metastatic colorectal cancer in the liver using TheraSphere®. Participation in the study involves an additional post-treatment SPECT/CT or PET/CT scan at (0-6) hours.

Number of Patients That Met the Criterion That the Dose Estimated With Tc-99m MAA SPECT Was Within 15% of the Dose Estimated From Y-90 SPECT

Change in dose estimates of radioactivity from Therasphere treatment to liver tumor target, measured in Gray, will be compared at pre-treatment and up to 6 hours post-treatment. Reported as number of patients that met the criterion that the dose estimated with Tc-99m MAA SPECT was within 15% of the dose estimated from Y-90 SPECT

Inclusion Criteria: The Diagnosis of metastatic colorectal cancer to the liver Patients with a diagnosis of metastatic colorectal cancer to the liver Liver metastases are unresectable Tumors are hypervascular based on visual estimation by the Investigator Target tumors are measurable using standard imaging techniques Performance Status Score 0 - 2 Age ≥18 years Life expectancy ≥3 months >4 weeks since prior radiation, surgery or chemotherapy Able to comprehend and provide written informed consent in accordance with institutional and federal guidelines At least one month has elapsed since most recent prior cancer therapy with the following exception: Patient is willing to participate in the study and has signed the study informed consent Exclusion Criteria: Patients may not be treated with TheraSphere® if patients have any of the following exclusions: Any pre-treatment laboratory findings within 15 days of treatment demonstrating liver dysfunction: Blood test result levels outside of the normal range Any history of hepatic encephalopathy Any contraindications to angiography and hepatic artery catheterization such as: History of severe allergy or intolerance to any contrast media, narcotics, sedatives or atropine that cannot be corrected or premedicated Bleeding diathesis, not correctable by usual forms of therapy Severe peripheral vascular disease that would preclude catheterization. Evidence of pulmonary insufficiency Significant extrahepatic disease representing an imminent life-threatening outcome Active uncontrolled infection Significant underlying medical or psychiatric illness Co-morbid disease or condition that would preclude safe delivery of TheraSphere® treatment or, in the judgment of the physician, place the patient at undue risk Pregnancy Special Categories of Patients: Not applicable Research in Mentally Disabled People: No. All participants or legal guardians will be fully able to give informed consent.