Evaluation of response to multikinase inhibitor in metastatic renal cell carcinoma by FDG PET/contrast-enhanced CT.

Objective: Multikinase inhibitor (MKI) is a promising drug for treatment of metastatic renal cell carcinoma (mRCC). We explained the usefulness of [¹⁸F]-2-fluoro-2-deoxyglucose positron emission tomography/contrast-enhanced computed tomography (FDG PET/CECT) for mRCC in evaluating the early response to MKI and in predicting progression-free survival (PFS).

Methods: Patients who planned MKI treatment for mRCC were included in this prospective study. FDG PET/CECT was performed before MKI treatment and after one cycle of MKI treatment. Evaluation of the response to MKI was assessed by PET according to the European Organization for Research and Treatment of Cancer, by CT according to the Response Evaluation Criteria in Solid Tumors and appearance of central hypoattenuation (CHA).

Results: Twelve patients were enrolled in the study. Equality of response evaluation between PET and CT was in 8 patients (partial response [PR]: 1, stable disease [SD]: 6, progressive disease [PD]: 1). Among the other 4 patients, PET showed 2 patients with PR and 2 patients with PD, in contrast to the CT finding of SD in all 4 patients. PFS according to PET response showed a statistically significant difference between PR and SD (P < 0.05) and between PR and PD (P < 0.05), but not between PR and SD (P = 0.083). Positive CHA in metastatic lesions after MKI treatment was confirmed in 8 patients. PFS with positive CHA was 233.8 days, while that without CHA was 75.0 days (P < 0.05).

Conclusions: FDG PET/CECT shows potential for evaluating early treatment response to MKI in mRCC and for predicting PFS.