Abstract P2-12-23: Changes in 18F-FDG-PET uptake after the first course of DTX reflect response to preoperative chemotherapy and prognosis in breast cancer

Abstract [Purpose] It is important to make early decisions about treatment changes in treatment-resistant groups. The aim of this study is to extract non-responders among preoperative chemotherapy using 18F-fluorodeoxyglucose positron-emission tomography (18F-FDG PET) in primary breast cancer. We hypothesized that early evaluation of FDG PET after the first course of docetaxel (DTX) would predict treatment resistant group by the relationship between changes on FDG accumulation and tumor diameter on magnetic resonance imaging (MRI). [Patients and Methods] Thirty-seven of 41 patients were evaluated. Clinical stage was T1-4, N0-3, and M0 between August 2007 and December 2010. Four courses of DTX were administered followed by 4 courses of fluorouracil/epirubicin/cyclophosphamide (FEC) followed by surgery. FDG-PET evaluation was performed by the maximum standardized uptake value (SUVmax). FDG-PET scans were performed at baseline, at 15 days after the first course of DTX (C1D15), and at 15 days after 4 courses of DTX (C4D15). Tumor reduction rate was measured on MRI at baseline and at C4D15 according to Response Evaluation Criteria in Solid Tumors (RECIST). ROC analysis was performed by between SUVmax of C1D15 and MRI of C4D15. Changes of SUVmax C1D15 were divided into high and low group by ROC analysis. Core needle biopsy (CNB) was performed to evaluate the treatment effect pathologically after 4 courses of DTX (C4CNB). The pathological treatment effect of surgical specimens after 4 courses of FEC (C4FEC) was also examined. The difference in progression-free survival (PFS) rate or overall survival (OS) rate between the low and high SUVmax of C1D15 change rate was calculated using Kaplan-Meier survival curves and compared by log-rank test. The protocol of the study was approved by the Ethics Committee of the Gunma Prefectural Cancer Center (ECGPCC), and all patients gave their written informed consent before enrollment (No. 19011). The observational study was also approved by ECGPCC (No. 30087). [Results] There were ER+HER2-:17, ER+HER2+:4, ER-HER2-:11, and ER-HER2+:5 cases. SUVmax change rate C1D15 correlated with the SUVmax change rate C4D15 and tumor shrinkage rate on MRI C4D15 in univariate (SUVmax C4D15: γ=.567, p<.001, MRI C4D15: γ=.748, p<.001) and in multivariate analysis (SUVmax C4D15: γ=414, p=.002, MRI C4D15: γ=.616, p<.001). The SUVmax change rate C1D15 correlated with pathological effect of C4CNB (γ=.392, p=.032) and of surgical specimen C4FEC (γ=.440, p=.006) in univariate analysis. From ROC analysis based on SUVmax C1D15 and MRI C4D15 (AUC=.924, 95% CI: .828-1.000, p<.001), the SUVmax C1D15 were divided into two groups with high and low SUVmax changes. The mean SUVmax in the low group (<30%) (n=15) was 15.8% (±9.7). The mean SUVmax in the high group (≥30%) (n=22) was 50.8% (±11.7). The mean of MRI change rate of C4D15 was 20.4% (±5.4) in the low SUVmax change group and 69.2% (±5.8) in the high SUVmax change group, showing a significant difference between the two groups (p<.001). The low SUVmax change group showed shorter PFS than the high SUVmax group (median 80.9 vs 93.7 months, p=.050), but there was no difference in OS (p=.719). [Conclusion] Changes less than 30% of 18F-FDG uptake after the first course of DTX may reflect the treatment resistance and poor prognosis in primary breast cancer. Citation Format: Tomoko Hirakata, Yasuhiro Yanagita, Tomomi Fujisawa, Teruhiko Kinoshita, Hiroyuki Horikoshi, Nariyuki Oya, Tsukasa Akiyoshi, Misa Iijima, Takeshi Miyamoto, Keiko Yanai, Hiroshi Matsumoto, Kenichi Inoue, Rie Horii, Takaaki Fujii, Ken Shirabe. Changes in 18F-FDG-PET uptake after the first course of DTX reflect response to preoperative chemotherapy and prognosis in breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-12-23.