Inclusion Criteria:
* Patients willing to participate and provide written consent
* Patients 18 years of age and older
* Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤2
* Biopsy confirmed RCC \> 4.0 cm and no renal vein or IVC involvement (T1b or T2 disease)
* Not suitable for or declining standard of care nephrectomy or partial nephrectomy
* Adequate hepatic function, defined by the following laboratory results:
* Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × upper limit of normal (ULN) (or ≤5 × ULN if presence of liver metastases)
* Total bilirubin ≤3 × ULN
* Serum albumin ≥3.0 g/dL unless prothrombin time (PT) is within the normal range
* Adequate hematologic function, defined by the following laboratory results:
* Hemoglobin concentration ≥8.0 g/dL
* Absolute neutrophil count (ANC) ≥1000 cells/µL (≥1000 cells/mm3 )
* Platelets \>50 × 109 /L (100 × 103 /mm3 )
* For women of childbearing potential (WOCBP):
* Negative serum pregnancy test within 48 hours prior to the first dose of study treatment
* Agreement to use barrier contraception and a second form of highly effective contraception (Clinical Trials Facilitation Group \[CTFG\] 2020) while receiving study treatment and for 7 months following their last dose of study treatment. Alternatively, total abstinence is also considered a highly effective contraception method when this is in line with the preferred and usual lifestyle of the subject. Periodic abstinence (e.g., calendar, ovulation, symptothermal, post-ovulation methods) and withdrawal are not acceptable methods of contraception.
* Sexually active male subjects must use a condom during intercourse while receiving treatment and for at least 120 days after the last dose of the study treatment and should not father a child during this period.
* Male study subjects whose sexual partners are WOCBP must also agree to use a second form of highly effective contraception (CTFG 2020) while receiving 90Y and for at least 4 months following their last dose. Alternatively, total abstinence is also considered a highly effective contraception method when this is in line with the preferred and usual lifestyle of the subject.
* Vasectomized men are also required to use a condom during intercourse, including with a male partner, to prevent delivery of the drug via seminal fluid.
Exclusion Criteria:
* Evidence of metastatic disease on CT or MRI
* Severely impaired renal function (GFR ≤ 30 mL/min/1.73m²) and not on dialysis
* Bilateral RCC without plan for definitive therapy of the contralateral lesion
* RCC that is locally recurrent at prior surgery or ablation site (new location in same or contralateral kidney is permitted)
* Prior or concurrent kidney radiation therapy or systemic immunotherapy/TKI
* Lung shunt with estimated lung radiation dose \> 30 Gy for single dose or \> 50 Gy total.
* Planning angiogram cone beam CT from all accessible feeding arteries shows lack of perfusion to all or portions of the RCC tumour such that, in the investigator's opinion, Y-90 radioembolization would result in substantial RCC tumour being untreated or receive an inadequate dose.
* Contraindication to arterial renal angiogram, or both CT and MRI contrast medium
* History of severe allergy to CT contrast medium or any study product ingredients that cannot be managed medically
* History of chronic lung disease with baseline oxygen saturation \< 90% or requiring home oxygen therapy.
* Congestive heart failure with ejection fraction \< 40%
* Presence of active infection, defined by the investigator as clinically significant.
* Any chronic condition that is severe or unstable and, in the opinion of the investigator, would put the patient at unacceptable risk of adverse event related to the Y-90 radioembolization procedure. Such conditions include but are not limited to: unstable angina, congestive heart failure, interstitial lung disease, severe gastrointestinal disease with diarrhea.
* Life expectancy \> 1 year
* Pregnant or breast-feeding patient
