Combined positron emission tomography/computed tomography in sunitinib therapy assessment of patients with metastatic renal cell carcinoma

Aim

To assess the clinical benefit of combined functional imaging with [¹⁸F]2-fluoro-2-deoxy-d-glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) in patients with metastatic renal cell carcinoma (mRCC) treated with the tyrosine kinase inhibitor sunitinib.

Materials and methods

Fourteen patients with mRCC were prospectively enrolled in this study. All patients underwent PET/CT before receiving at least two cycles of sunitinib treatment. Three months after the onset of sunitinib treatment, a second PET/CT was carried out. The metabolic response evaluated from the PET (standard uptake value; SUV) was compared with the CT component of the PET/CT. The Response Evaluation Criteria in Solid Tumours criteria were used to assess the CT response and modified European Organization for Research and Treatment of Cancer criteria were used to assess the PET response.

Results

Three main results were obtained: (1) Patients with relatively low 18F-FDG uptake before treatment (SUV < 5) had a longer progression-free survival than those with a relatively high 18F-FDG uptake (P = 0.006). (2) Patients with a partial metabolic response or stable metabolic disease after two courses of sunitinib had improved prognosis as compared with those with progressive metabolic disease (P = 0.031). (3) There was a clear discrepancy between PET and CT as a tool for the evaluation of treatment response after two courses of sunitinib. PET indicated progressive disease in three patients, a partial response in six patients and stable disease in four patients. In contrast, CT concluded with progression in only one patient and stable disease in all other patients.

Conclusion

In patients with mRCC, a high baseline 18F-FDG uptake indicates aggressive disease, and the degree of reduction in 18F-FDG uptake after sunitinib treatment adds valuable prognostic information. Hence, the inclusion of PET results seems to improve the clinical counselling of patients with mRCC. Larger studies are needed to confirm these findings.