THERASPHERE VS SIR-SPHERES:
WHICH Y-90 PLATFORM IS USED FOR YOUR CASE?
The two commercially available Y-90 microsphere platforms differ in composition, physical properties, dosimetry approach, and approved indications. This guide explains what distinguishes them and how the treating team selects between them.
analyticsAt a Glance
- check_circleTheraSphere uses glass microspheres; SIR-Spheres uses resin microspheres โ different physics, different clinical behaviour
- check_circleGlass spheres are smaller and more radioactive per sphere; resin spheres are larger with greater embolic effect
- check_circlePlatform selection is driven by indication, lung shunting fraction, liver function, and institutional expertise
- check_circleBoth platforms deliver Y-90 beta radiation โ clinical outcomes are broadly similar across most indications
TheraSphere vs SIR-Spheres: Head-to-Head Comparison
A structured technical comparison of the two commercially available Y-90 platforms across the properties most relevant to clinical decision-making.
| Parameter | TheraSphere (Glass) | SIR-Spheres (Resin) |
|---|---|---|
| Manufacturer | BTG / Boston Scientific | Sirtex Medical |
| Microsphere material | Borosilicate glass | Biocompatible ion-exchange resin |
| Microsphere diameter | 20โ30 ยตm | 20โ60 ยตm (mean ~32 ยตm) |
| Activity per microsphere | ~2,500 Bq (high activity) | ~50 Bq (low activity) |
| Spheres per typical dose | ~1โ8 million | ~40โ80 million |
| Embolic effect | Minimal (radiation dominant) | Significant (dual: radiation + embolization) |
| Dosimetry approach | MIRD, partition model, BSA method | BSA method; partition model also used |
| Regulatory approval (USA) | FDA HDE โ primary/secondary liver tumours | FDA PMA โ colorectal liver metastases |
| Regulatory approval (EU/China) | CE mark / NMPA approval | CE mark / NMPA approval |
| Post-implant imaging | Bremsstrahlung SPECT/CT; Y-90 PET | Bremsstrahlung SPECT/CT; Y-90 PET |
| Primary clinical evidence base | HCC (SARAH; retrospective TheraSphere data) | CRLM (SIRFLOX, FOXFIRE, FOXFIRE Global); HCC (SIRveNIB) |
Glass vs Resin โ Clinical Implications
The physical differences between glass and resin microspheres translate into distinct clinical behaviour and different situations where each platform performs best.
TheraSphere (Glass) โ Strengths
- Preferred in portal vein thrombosisLower sphere count per dose means less embolic effect โ preserving residual portal flow in patients where hepatic artery is the dominant blood supply due to PVT.
- Dose escalation is practicalHigh activity per sphere makes it technically feasible to deliver very high ablative doses (>200 Gy) to small, isolated HCC nodules โ a strategy particularly relevant in radiation lobectomy/segmentectomy.
- Radiation segmentectomy and lobectomyTheraSphere's high-dose-per-sphere profile is preferred for radiation segmentectomy (selective ablation of a tumour-bearing segment) and radiation lobectomy (inducing contralateral liver hypertrophy before surgery).
- Better for patients with compromised liver functionMinimal embolic effect reduces acute post-procedural liver injury โ important in Child-Pugh B HCC patients where additional hepatic insult is more consequential.
SIR-Spheres (Resin) โ Strengths
- Primary evidence base for CRLMSIR-Spheres has the largest randomised trial base in colorectal liver metastases โ SIRFLOX and FOXFIRE Global are the pivotal Phase III CRLM trials and both used SIR-Spheres.
- Greater embolic contribution to tumour killThe higher sphere count provides meaningful tumor devascularization on top of radiation โ potentially advantageous in hypervascular tumour types where embolization alone can achieve partial response.
- Wider vascular distributionLarger sphere count means wider distribution across the tumour vasculature โ potentially providing more homogeneous coverage in large or heterogeneously vascularised tumours.
- Longer established supply chainSIR-Spheres has a longer global commercial history and supply infrastructure โ available at a broader range of international centres outside specialist Y-90 programmes.
Key Trial Evidence by Platform and Indication
The major randomised clinical trials that define the evidence base for each platform โ TheraSphere and SIR-Spheres have different primary evidence bases across indications.
HCC โ SARAH Trial (TheraSphere vs Sorafenib)
TheraSphere Y-90 vs sorafenib in advanced HCC. No significant OS difference, but meaningful quality of life advantage for Y-90 and better tolerability. Source: Vilgrain et al., Lancet Oncol 2017.
- Median OS: TheraSphere Y-908.0 months
- Median OS: sorafenib9.9 months
- Quality of Life advantageY-90 significantly better
CRLM โ SIRFLOX Trial (SIR-Spheres + FOLFOX vs FOLFOX)
SIR-Spheres + mFOLFOX6 vs mFOLFOX6 alone in first-line colorectal liver metastases. Source: van Hazel et al., JCO 2016.
- Median PFS at liver (SIR-Spheres + FOLFOX)20.5 months
- Median PFS at liver (FOLFOX alone)12.6 months
How Your Treating Team Selects the Platform
Platform selection in clinical practice is rarely a binary patient choice โ it is primarily determined by the treating team based on indication, available dosimetry expertise, and institutional experience. These are the factors that guide the decision.
- 1
Clinical Indication
For CRLM, SIR-Spheres has the definitive Phase III trial evidence base. For HCC radiation segmentectomy or lobectomy, TheraSphere is preferred for its high-dose capability. For NET liver metastases and iCCA, both platforms are used โ institutional preference dominates.
- 2
Portal Vein Thrombosis Status
Patients with significant portal vein thrombosis are generally better served by TheraSphere (lower embolic load) โ additional hepatic artery embolization in the context of PVT carries higher ischaemic risk.
- 3
Liver Function (Child-Pugh)
Child-Pugh B patients tolerate the embolic component of SIR-Spheres less well โ TheraSphere's minimal embolic effect makes it safer in patients with marginal liver reserve.
- 4
Treatment Intent
Ablative intent (radiation segmentectomy, high-dose tumour kill) favours TheraSphere. Combination with chemotherapy for CRLM favours SIR-Spheres based on trial evidence.
- 5
Institutional Availability and Expertise
Many centres specialise in one platform โ dosimetry protocols, activity ordering logistics, and operator familiarity all influence outcomes. The best outcomes at a given centre come from the platform that centre uses most.
TheraSphere vs SIR-Spheres โ Key Physical Comparison Numbers
The most important quantitative differences between the two platforms.
- ~2,500 Bq vs ~50 BqActivity per microsphere: TheraSphere vs SIR-SpheresTheraSphere carries 50ร more radioactivity per sphere โ enabling high-dose ablation with far fewer spheres; SIR-Spheres achieves dose through volume.
- 20โ30 ยตm vs 20โ60 ยตmSphere diameter: TheraSphere vs SIR-SpheresSmaller TheraSphere spheres penetrate further into tumour microvasculature; larger SIR-Spheres produce a more pronounced embolic effect at arteriolar level.
- Both: ~64 hrsY-90 half-life โ same for both platformsDespite different physical properties, both platforms use yttrium-90 with the same physical half-life โ dose delivery kinetics are identical.
More from the TARE / Y-90 Resource Library
Continue exploring Y-90 radioembolization โ from the patient introduction and physics to pre-treatment workup and dosimetry calculation.
Frequently Asked Questions: TheraSphere vs SIR-Spheres
Can I request a specific platform for my treatment?
Patients can express a preference, and a well-informed discussion with your interventional radiologist about platform rationale is entirely appropriate. However, the treating team's final decision should be clinically driven โ the platform used by the treating centre with the greatest expertise and best outcomes for your specific indication is the right choice. If a centre only uses one platform and you have concerns about whether it is appropriate for your case, CancerFax can identify centres in China and India that have experience with both TheraSphere and SIR-Spheres and can review which is more suitable for your tumour profile.
Is TheraSphere or SIR-Spheres better for HCC?
Neither platform has demonstrated a definitive clinical superiority over the other in HCC โ both SARAH (TheraSphere) and SIRveNIB (SIR-Spheres) showed comparable OS to sorafenib without superiority in Phase III trials. The choice for HCC in clinical practice is driven by: TheraSphere for radiation segmentectomy, high-dose ablation, and Child-Pugh B patients; SIR-Spheres for standard BCLC B lobar treatment at centres with SIR-Spheres expertise. In most retrospective comparative analyses, outcomes are similar when dosimetry is performed correctly for either platform.
Which platform is used in China?
Both TheraSphere and SIR-Spheres hold NMPA approval in China and are available at major interventional oncology centres. The most experienced Chinese centres โ including those in Beijing, Shanghai, and Guangzhou โ work with both platforms and select based on clinical indication and dosimetry approach. CancerFax confirms platform availability at the recommended Chinese centre as part of the pre-treatment coordination process.
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Wondering Which Y-90 Platform Is Right for Your Liver Cancer?
CancerFax reviews your liver tumour records and connects you with interventional oncology specialists at Chinese and Indian centres who use both TheraSphere and SIR-Spheres โ ensuring platform selection is clinically driven.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified interventional radiologist before making treatment decisions.