The value of serial [⁶⁸Ga]Ga-FAPI-04 PET/CT in predicting pathological response and evaluating therapeutic efficacy to neoadjuvant chemotherapy in breast cancer

Abstract

Objective: To investigate the clinical utility of serial [⁶⁸Ga]Ga-FAPI-04 PET/CT for predicting pathological response and evaluating therapeutic efficacy in breast cancer (BC) patients receiving neoadjuvant chemotherapy (NAC).

Methods: A total of 64 biopsy-confirmed patients with BC were retrospectively included. Serial [⁶⁸Ga]Ga-FAPI-04 PET/CT scans were conducted at three time points: prior to NAC (baseline, PET₁), after two cycles of NAC (interim, PET₂), and before surgery (pre-surgery, PET₃). PET/CT parameters derived from the primary BC lesions were recorded before and after NAC. The changes in these parameters were compared between the pathological complete response (pCR) and the non-pCR group. Logistic regression was used to assess the predictive value of [⁶⁸Ga]Ga-FAPI-04 PET/CT parameters for predicting pCR. Receiver operating characteristic (ROC) curve analysis was employed to determine the optimal cutoff values for predicting pCR. DeLong's test was applied to statistically assess differences in the area under the ROC curves (AUC).

Results: Significant reductions in [⁶⁸Ga]Ga-FAPI-04 PET/CT parameters (ΔSUVmax, ΔSUVmean, ΔFTV, ΔTLF) were observed among all patients, with significantly greater decreases in the pCR group compared to the non-pCR group (all P < 0.001). In the non-pCR group, the total FTV (ΔtFTV_1-2 and ΔtFTV_1-3) of primary breast lesions and metastatic lymph nodes showed moderate correlation with the residual cancer burden (RCB) score. Multivariate logistic regression identified ΔSUVmean_1-2 (P = 0.027), ΔFTV_1-2 (P = 0.006), ΔSUVmean_1-3 (P = 0.032), and ΔFTV_1-3 (P = 0.010) as independent predictors for predicting pCR. On the basis of the ROC curve analysis, ΔSUVmean_1-3 (AUC = 0.848) and ΔFTV_1-3 (AUC = 0.906) showed slightly higher predictive performance than ΔSUVmean_1-2 (AUC = 0.825) and ΔFTV_1-2 (AUC = 0.869), respectively, but the difference was not statistically significant (P > 0.05).

Conclusion: This study demonstrates that serial [⁶⁸Ga]Ga-FAPI-04 PET/CT facilitates early prediction of pathological response to neoadjuvant chemotherapy in breast cancer, as well as assessment of therapeutic efficacy. Prospective studies with larger samples are needed.

Keywords: Breast neoplasm; Neoadjuvant chemotherapy; PET/CT; Pathological response; [68Ga]Ga-FAPI-04.