Abstract P6-02-09: Diagnostic performance of dedicated breast PET for the prediction of pathological response after neoadjuvant chemotherapy

Abstract

Abstract Background: Neoadjuvant chemotherapy (NAC) is a standard treatment for operable breast cancer. However, imaging methods for evaluating treatment response have not been established. Previous studies reported that ring-type dedicated breast positron emission tomography (DbPET) detected residual tumors following NAC more accurately than whole-body PET/CT. This study assessed DbPET parameters for predicting pathological complete response (pCR) in patients with breast cancer. Patients and Methods: Among patients with breast cancer who underwent surgery after NAC, 61 were examined using ring-type DbPET before and after NAC. The maximum standardized uptake values (SUVmax) and tumor-to-normal-tissue ratio (TNR) were calculated before and after NAC (pre-SUVmax, pre-TNR, post-SUVmax and post-TNR, respectively). Moreover, the reduction rates (ΔSUVmax and ΔTNR) were determined. pCR was defined as complete remission of breast cancer. Results: The median patient age was 52 years. Forty patients (65.6%) were estrogen receptor (ER)-positive, whereas 25 patients (41.0%) were HER2-positive. Fifteen patients (24.6%) achieved pCR after NAC. The calculated values for the parameters of DbPET are summarized in Table 1. The most promising parameters for predicting pCR were ΔSUVmax (area under the curve [AUC]: 0.506) and post-TNR (AUC: 0.640). Although neither of these two parameters reflected the pathological response to NAC in patients with ER-positive disease, post-TNR showed the highest AUC (i.e., AUC: 0.750) for pCR in patients with ER-negative disease. The sensitivity and specificity of post-TNR in the ER-positive group were 85.7% and 39.4%, respectively. In the ER-negative group, these values were 100% and 58.3%, respectively [Table 2] Table 1.Diagnostic performance of dedicated breast positron-emission tomography for the prediction of pathological complete response after neoadjuvant chemotherapyParameterspCR Median (IQR)Non-pCR Median (IQR)PAUC (95% CI)Pre-SUVmax14.8 (9.2–17.7)14.4 (10.7–19.8)0.6040.454 (0.285–0.624)Post-SUVmax1.8(1.5–2.1)2.0 (1.6–3.4)0.2370.603 (0.460–0.746)ΔSUVmax (%)87.32 (81.5–91.8)88.6(82.8–91.8)0.9540.506 (0.329–0.682)Pre-TNR8.0 (5.3–9.2)7.3(5.9–10.2)0.7570.472 (0.297–0.647)Post-TNR1.7(1.0–1.1)1.2 (1.0–2.4)0.0980.640 (0.506–0.774)ΔTNR (%)87.3 (78.3–89.1)79.8 (62.7–86.7)0.1130.638 (0.472–0.803)pCR, pathological complete response; IQR, interquartile range; AUC, area under the curve; CI, confidence interval, SUV, standardized uptake value; TNR, tumor-to-normal-tissue ratio.Table 2.Diagnostic accuracy of post-TNR according to estrogen receptor status Sensitivity (%)Specificity (%)Accuracy (%)PPV (%)NPV (%)ER-positive85.739.447.523.192.9ER-negative10058.375.061.5100TNR, tumor-to-normal-tissue ratio; ER, estrogen receptor; PPV, positive predictive value; NPV, negative predictive value Conclusion: In DbPET, ΔSUVmax and post-TNR were shown to be promising parameters for predicting pathological response to NAC. Post-TNR provided the highest sensitivity for predicting pCR in patients with ER-negative breast cancer. Citation Format: Suzuki E, Sasada S, Sueoka S, Masumoto N, Goda N, Kajitani K, Emi A, Haruta R, Kadoya T, Kataoka T, Okada M. Diagnostic performance of dedicated breast PET for the prediction of pathological response after neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-02-09.