The potential clinical value of FDG-PET for recurrent renal cell carcinoma

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Abstract

Purpose

The clinical value of positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) for follow-up or suspected recurrence of renal cell carcinoma (RCC) has not been fully evaluated. The purpose of this study was to assess the diagnostic performance of FDG-PET for postoperative assessment in patients with RCC.

Methods

We reviewed 28 scans in 23 patients who had undergone FDG-PET scans after surgery for RCC. Diagnostic accuracy of visually interpreted PET was evaluated based on final diagnoses obtained histologically or by clinical follow-up at least 6 months. Also, additional information over CT, influence on treatment decisions, and the accuracy of FDG uptake as a predictor of survival were assessed.

Results

Recurrence of renal carcinoma was histologically (n = 15) or clinically (n = 6) confirmed in 21 of 28 cases. Overall, the sensitivity, specificity, and diagnostic accuracy using FDG-PET were 81%, 71%, and 79%, respectively. In papillary RCC, the sensitivity was 100%; however, that was 75% in clear cell RCC in patient-basis. PET correctly detected local recurrence and metastases in all cases in the peritoneum, bone, muscle and adrenal gland. Additional information was obtained from scans in 6 cases (21%), which influenced therapeutic management in 3 cases (11%). Cumulative survival rates over 5 years in the PET-positive vs. the PET-negative group were 46% vs. 83%, respectively (p = 0.17).

Conclusions

FDG-PET would be useful for postoperative surveillance in patients with RCC, although its impact on treatment decisions may be limited. Further investigations are necessary to conclude whether PET has a prognostic value.

Introduction

Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) has been widely used in clinical oncology as an established modality for imaging cancer. FDG-PET is applicable especially for staging or re-staging, and monitoring therapeutic response in several cancers. As for renal cell carcinoma (RCC), Wahl et al. reported the feasibility of metabolic imaging using FDG, as well as morphological imaging for primary and metastatic tumors in their pilot study in 1991 [1], followed by reports describing high accuracy of FDG-PET for the diagnosis of RCC [2], [3], [4]. Conversely, other reports have indicated higher false-negative rates [5], [6]. Kang et al. examined 90 PET scans in 66 patients, and concluded that the role of FDG-PET in the detection of RCC was limited due to its low sensitivity and that, with superior specificity; PET might have a complementary role as a problem-solving tool in cases that were equivocal using conventional imaging [7]. Thus, the clinical role of FDG-PET for RCC remains controversial, but has not been considered helpful for the evaluation of primary RCC.

Meanwhile, the role of FDG-PET for follow-up or suspected recurrence of RCC has been reported to be favorable [8], [9], [10]. Clinical courses in patients with recurrent RCC following nephrectomy vary, with a survival benefit associated with sufficient metastasectomy [11], [12], [13], [14], [15]. More accurate diagnosis of recurrent RCC is important, but morphological imaging modalities, such as computed tomography (CT), have certain limitations for exact evaluation of recurrent RCC. Hence, metabolic imaging, including FDG-PET, is expected to demonstrate increased accuracy, but not much has been reported yet on the efficacy of PET in the diagnosis of recurrent RCC.

In the present study, to elucidate the clinical value of FDG-PET for recurrence and distant metastases of RCC, we assessed diagnostic performance of FDG-PET for postoperative survey in patients with RCC. Furthermore, we assessed whether FDG uptake could be a predictor of survival in patients with recurrent RCC.

Section snippets

Patients

Between August 2000 and January 2008, 39 patients underwent 45 FDG-PET scans at our institute in order to investigate RCC. Among them, 8 patients (undergoing 8 scans) did not histologically prove to have RCC because they did not undergo surgery or biopsy, 1 patient (undergoing 1 scan) had bilateral renal tumors, one of which was not histologically proven, and 6 patients (undergoing 7 scans) had synchronous double cancer. These patients were excluded in our study. In this retrospective study, we

Results

We evaluated a total of 28 PET scans in 23 patients and excluded 1 patient (using the Advance scanner) without definite final diagnosis. The patients’ profile and their clinical outcome are shown in Table 1. Of 28 cases, 21 were finally confirmed to be in recurrence via surgery (n = 7), biopsy (n = 8), and clinical follow-up (n = 6), i.e. the tumor had increased in size. The remaining 7 cases were considered negative for recurrence. Histopathology demonstrated that the type of recurrent cases were

Discussion

The overall diagnostic performance of FDG-PET for recurrent RCC after nephrectomy was reasonably high, with a case-based sensitivity of 81%, specificity of 71%, and accuracy of 79%, which was considered comparable with those for other malignancies. These data indicate that FDG-PET would be a useful tool for postoperative surveillance even in patients with RCC.

The role of FDG-PET for re-staging of RCC was initially examined by Safaei et al., who examined 36 patients and demonstrated the

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