Evaluating tumor response with FDG PET: updates on PERCIST, comparison with EORTC criteria and clues to future developments

Abstract

Eighteen years ago, the EORTC PET criteria standardized for the first time response assessment by FDG PET. Response assessment by FDG PET has been further developed and refined by PERCIST (PET response criteria in solid tumors). This review describes the data underlying these two systems for assessing tumor response on FDG PET/CT. It also summarizes recent clinical studies that have compared EORTC criteria and PERCIST with each other as well as with the anatomically based "response criteria in solid tumors" (RECIST). These studies have shown that response assessment by EORTC criteria and PERCIST leads to very similar response classifications. In contrast, there are significant differences between response assessment by PERCIST and RECIST. Preliminary data also suggest that response assessment by PERCIST is better correlated with patient outcome and may be a better predictor for the effectiveness of new anti-cancer therapies than RECIST. If correct, this could have a significant impact on oncologic drug development. However, confirmation of the better predictive value of response assessment by PERCIST by data from randomized trials is still lacking.

Keywords: EORTC criteria; FDG PET; Oncology; PERCIST; Treatment monitoring.

Conflict of interest statement

Conflict of Interest: Author Katja Pinker declares that she has no conflict of interest. Author Christopher C Riedl declares that he has no conflict of interest. Author Wolfgang A Weber declares that he has no conflict of interest.

Figures

Figure 1

Lesion selection for response assessment by PERCIST. Images show MIP projection of FDG PET/CT images of a woman with right breast cancer and contralateral lymph node metastases. On the baseline images (A) the primary tumor shows the highest FDG uptake and is used as the target lesion (red arrow). On the follow-up study the highest FDG uptake is seen in the contralateral lymph node metastasis (red arrow) which is the target lesion for the follow-up scan (B). The change in tumor FDG uptake is calculated as (SULpeak(lymph node - SULpeak(breast)) / SULpeak(breast)

Figure 2

Differences in response assessment depending on the number of lesions analyzed. The liver metastasis (red arrow) is the lesion with the highest uptake on the baseline (a) and follow-up scan (b). It showed no significant change in FDG uptake, SULpeak 11.4 and 9.9, respectively (−12%). However, if five lesions are selected as target lesions (green arrows) the sum of these five lesions decreases by 32%. -

Figure 3

Prediction of tumor survival by tumor response. Survival of patients with metastatic breast cancer undergoing dose intensified (experimental group) or standard chemotherapy (control) from a meta-analysis of 10 randomized trials including a total of 2126 patients. On a patient level (a) survival is clearly better for responders (R) than for nonresponders (NR). However, on a trial level (b) there is only a weak correlation between the improvement in response rate (shown on the x-axis) and the improvement in survival (shown on the y-axis) Figure 3 from Bruzzi et al. [35], edited. Arrows indicate studies that showed no improved survival despite an improvement in response rate.