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Internal view of patient's torso demonstrating targeted accuracy of TheraSphere Y-90 Glass Microspheres in liver.

TheraSphere™ Y-90 Glass Microspheres

RASER study

Radiation segmentectomy for curative intent of unresectable very early to early stage hepatocellular carcinoma (RASER): a single-center, single-arm study

First prospective study to assess outcomes after radiation segmentectomy (RS) in patients with very early or early stage hepatocellular carcinoma which showed 100% initial objective response with TheraSphere Y-90 glass microspheres.

Kim E, Sher A, Abboud G, et al. Radiation segmentectomy for curative intent of unresectable very early to early stage hepatocellular carcinoma (RASER): a single-centre, single-arm study [published online ahead of print, 2022 May 23]. Lancet Gastroenterol Hepatol. 2022;S2468-1253(22)00091-7. doi:10.1016/S2468-1253(22)00091-7

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Download RASER data sheet


The aim of this study was to assess the safety and efficacy of RS in patients with unresectable hepatocellular carcinoma (HCC) deemed unfavorable for ablation. The study provides a strong rationale for new randomized trials comparing RS to ablation and supports inclusion of RS in BCLC guidelines.


Primary endpoint: Target tumor response measured by modified RECIST (mRECIST).

Secondary endpoints: Time to progression (TTP) of the target lesion and overall disease, and adverse events using CTCAE version 5.0.

CTCAE = National Cancer Institute Common Terminology Criteria for Adverse Events

Study design and methods


The study included adults (>18 years) with solitary HCC with unfavorable location for ablation, without metastasis or macrovascular invasion. Eligibility criteria included measurable disease ≤ 3 cm in diameter, Child-Pugh score A–B7, an ECOG score of 0, and adequate hematological and organ function. Of the 44 individuals assessed for eligibility, 29 patients were included in the study. Patients were followed up with imaging and office visits for up to 24 months.

Key results

Liver Transplant Necrosis

Graph showing 27% (8/29) liver transplant % and 100% (8/8) pathological necrosis rate of target lesions.

Eight patients received a liver transplant. Pathology results show all eight target lesions had 100% necrosis.

Target lesion response

% of participants (n=29)

Initial objective response100% (29) 
Initial complete response83% (24) 
Partial response
17% (5)
Sustained complete response90% (26)
Median time: 43 days
Median duration: 635 days


Target lesion & overall disease progression

% of participants (n=29)

Target lesion progression10% (3) 
Cumulative incidence of target lesion progressionYear 1: 4%
Year 2: 12%
Actuarial overall survivalYear 1: 96%
Year 2: 96%
Overall progression31% (9) 
Cumulative incidence of overall progressionYear 1: 14%
Year 2: 27%

Low proportion of high-grade adverse events* (AEs)

% of participants (n=29)

Grade 3 Leukopenia14% (4)
Grade 3 Thrombocytopenia7% (2)
Grade 3 Non-laboratory-related adverse events7% (2)

*A complete list of adverse events can be found in Table 2 in the publication

Participant demographics

SexMale: 23/29 (79%)
Female: 6/29 (21%)
Child-PughA5: 14/29 (48%)
A6: 12/29 (41%)
B7: 3/29 (10%)
Mean perfused Liver volume153.6 mL (mean SD 99.2)
Median tumoral dose delivered1004.6 Gy (95% CI [190.8–3730.0])


  • In this study, radiation segmentectomy with TheraSphere Y-90 glass microspheres was shown to be effective, with a low proportion of high-grade adverse events in patients with unresectable very early to early-stage hepatocellular carcinoma with suboptimal location for ablation.
  • Sustained complete response rates and local progression of the target lesion were similar to the previously reported rates after thermal ablation.**
  • Given complete pathological necrosis of the explanted tumors, larger investigative studies on the curative potential of radiation segmentectomy are warranted.

**References results cited in the publication.