Abstract 308P
Background
This study aimed to compare contrast-enhanced CT (CE-CT) and FDG-PET/CT for response monitoring in metastatic breast cancer (MBC) using the standardized response evaluation criteria RECIST 1.1 and PERCIST. The objective was to analyze if FDG-PET/CT detected progressive disease earlier than CE-CT.
Methods
Women with MBC were enrolled prospectively and monitored using a combined CE-CT and FDG-PET/CT scan every 9-12 weeks to evaluate response to first-line treatment. CE-CT scans and RECIST 1.1 were used for clinical decision-making without access to the FDG-PET/CT scans. At completion, FDG-PET/CT scans were unblinded and assessed according to PERCIST. Visual assessment was used if response criteria could not be applied. Paired comparative analyses for CE-CT vs. FDG-PET/CT were applied. The primary endpoint was the first detection of progression, and the secondary endpoints were time to detection of progression and the number of scans with measurable disease.
Results
A total of 87 women were enrolled in the study with a median of six (range 1-11) follow-up scans. Their distribution according to progression is seen in the table. Progression was detected first by FDG-PET/CT in 43/87 patients (49.4%) while CE-CT detected progression first in 1/87 patients (1.11%) (p < 0.0001). Excluding patients without progression (n=32), progression was seen first by FDG-PET/CT in 78% (43/55). On average, progression was seen in two follow-up scans (range 1-4) earlier on FDG-PET/CT than on CE-CT. Of 87 patients, 76 (87.4%) had measurable disease according to PERCIST and 51 (58.6%) according to RECIST 1.1. Table: 308P
| N (%) | |
| Progression on both modalities simultaneously | 11 (12.6) |
| Progression on both modalities, seen first on FDG-PET/CT | 26 (29.9) |
| Progression on both modalities, seen first on CE/CT | 0 (0.00) |
| Progression on FDG-PET/CT only | 17 (19.5) |
| Progression on CE/CT only | 1 (1.1) |
| No progression on both modalities | 32 (36.8) |
| 87 (100) |
Conclusions
In most patients, FDG-PET/CT detected progression earlier than CE-CT, FDG-PET-CT being later only in one. Using FDG-PET/CT offers the opportunity to optimize treatment planning allowing earlier termination of ineffective toxic treatments for MBC. The question about the magnitude of the final benefit for patients is a perspective for future research.
Clinical trial identification
NCT03358589.
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Qvesehls grant Mrs. Astrid Thaysens grant The Independent Research Fund Denmark (DFF – 7016-00359) University of Southern Denmark (Ph.D. grant) Odense University Hospital (Ph.D. grant) Center for Personalized Response Monitoring in Oncology (PREMIO), Odense University Hospital, Odense, Denmark.
Disclosure
All authors have declared no conflicts of interest.