CABOSUN: a phase II trial of CABOMETYX® (cabozantinib) in treatment-naïve advanced RCC

In the pivotal, phase II, CABOSUN study, the efficacy and safety of cabozantinib was compared with sunitinib in the first-line treatment of advanced RCC.1, 7, 8

View the CABOSUN study publication

Study design

CABOSUN was a randomised, open-label multicenter phase II trial supported by grants from the National Institutes of Health and run independently of Ipsen. The study compared the efficacy and safety of cabozantinib with sunitinib as initial targeted therapy in adult patients with metastatic RCC of intermediate or poor risk, as defined by International Metastatic RCC Database Consortium (IMDC) criteria.1,7

Patients (n=157) were randomised 1:1 to receive either cabozantinib 60 mg/day (n=79) or sunitinib 50 mg/day, 4 weeks on, 2 weeks off (n=78). Random assignment to treatment was stratified by IMDC risk category (intermediate or poor) and presence of bone metastases (yes or no) using the dynamic allocation method.1,7

The primary endpoint of the CABOSUN trial was investigator-assessed PFS. Secondary endpoints were overall survival (OS), investigator-assessed objective response rate (ORR) and safety. PFS, ORR and best change in tumour target lesions by independent review were post-hoc retrospective analyses which were initiated after analysis of the primary endpoint.1,7

Design of the CABOSUN phase II trial

IMDC, International Metastatic RCC Database Consortium; ORR, objective response rate; OS, overall survival; PFS, progression-free survival; RCC, renal cell carcinoma

Adapted from SmPCand Choueiri TK, et al. 20177

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Study design

Patient population

Eligible patients were:

  • Age ≥18 years
  • Advanced or metastatic RCC with a clear-cell component
  • Measurable disease as defined by RECIST v1.1
  • No prior systemic treatment
  • Classified as intermediate or poor risk by IMDC criteria
  • ECOG performance status of 0 to 2
  • Adequate organ and marrow function

The patient demographic and baseline characteristics were similar between the cabozantinib and sunitinib treatment arms.1

Patient demographic and baseline characteristics in the CABOSUN phase II trial






Gender, n (%)
Male 66 (84) 57 (73)
Female 13 (16) 21 (27)
Age, years
Median 63 64
Range 56-69 57-71
IMDC risk group, n (%)
Intermediate 64 (81) 63 (81)
Poor 15 (19) 15 (19)
Bone metastases, n (%)
Yes 29 (37) 28 (36)
No 50 (63) 50 (64)
Prior nephrectomy
Yes 57 (72) 60 (77)
No 22 (28) 18 (23)
0 36 (46) 36 (46)
1 33 (42) 32 (41)
2 10 (13) 10 (13)

ECOG PS, Eastern Cooperative Oncology Group performance score; IMDC, International Metastatic Renal Cell Carcinoma Database Consortium

Adapted from Choueiri TK, et al. 20177

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Patient population

Key efficacy results

Primary endpoint: investigator-assessed PFS

Cabozantinib demonstrated significantly improved median PFS vs. sunitinib: 8.3 months for cabozantinib vs. 5.4 months for sunitinib (adjusted HR for progression or death: 0.56; 95% CI: 0.37-0.83; p=0.0042).1

A statistically significant improvement in PFS as retrospectively assessed by a blinded Independent Radiology Committee (IRC) was demonstrated for cabozantinib compared to sunitinib (8.6 months for cabozantinib vs 5.3 months for sunitinib). Aadjusted HR for progression or death: 0.48; 95% CI: 0.32-0.73; p=0.0005.1

The primary endpoint was investigator-assessed PFS. Secondary efficacy endpoints were objective response rate (ORR) and overall survival (OS). Tumor assessments were conducted every 12 weeks.

IRC-assessed PFS in the CABOSUN phase II trial (exploratory)*

This was a retrospective, exploratory analysis conducted by an independent radiology review committee involving all 157 randomised patients.

Adapted from SmPC1

PFS results for the prespecified subgroups of IMDC risk groups and presence or absence of bone metastases were consistent with those of the overall population.7


The study was not powered for the OS analysis and the data are immature. Cabozantinib treatment was associated with a trend for longer survival compared to sunitinib: 30.3 vs 21.0 months, adjusted HR: 0.74; 95% CI: 0.47-1.14).


A greater number of patients had an investigator-assessed ORR when treated with cabozantinib (n=79) compared with sunitinib (n=78): 33% (n=26) for cabozantinib vs. 12% (n=9) for sunitinib.1

Similar ORR results were reported in a retrospective, exploratory analysis conducted by the IRC; 20% (n=16) for cabozantinib vs. 9% (n=7) for sunitinib.1

ORR in the CABOSUN phase II trial

IRC, Independent radiology review committee; ORR, objective response rate

Adapted from SmPC1

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Key efficacy results

Safety results

Please see the ‘What are the adverse events of CABOMETYX®?’ and ‘What are the dosing recommendations for CABOMETYX®?’ sections of this website.

Please also refer to the CABOMETYX® Summary of Product Characteristics for a full list of adverse events and dose reduction recommendations.

For further information on the CABOSUN trial, please refer to full published clinical papers.7,8

View References →

Safety results

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