Value of ¹⁸F-FDG PET-CT Metabolic tumor volume in evaluating neoadjuvant chemotherapy efficacy in breast cancer

Objectives To determine the value of applicating ¹⁸F-FDG PET/CT metabolic tumor volume(MTV) early predict the efficacy of neoadjuvant chemotherapy(NAC) in breast cancer. By comparing the efficiency on prediction of NAC between MTV and maximum standard uptake value (SUVmax), to select the most suitable index and the specific values to evaluate the therapeutic effect

Methods In a prospevtive study, ¹⁸F-FDG PET-CT scans were performed in 57 women with primary breast cancer before NAC, after the first and the second cycle of NAC respectively. We’ve selected SUV=1.5 and 2.5 as the boundary respectively as the background subtraction, and calculated the change rate of MTV in different cycles of NAC. All patients was divided into two groups: tumor diameter < 2.5cm group, and tumor diameter ≥2.5cm group, and compared the change rate of MTV and SUVmax between them respectively.Pathological classification have been done according to the Miller and Panye grading system to NAC in breast cancer.

Results ⊿SUV_max1%(t=3.440, p=0.002), ⊿SUV_max2% (t=2.764, p=0.013) and ⊿MTV₂₂% when SUV=2.5 as the boundary (t=4.912, p=0.000) after the second cycle of NAC were statistically significant differences between effective group and ineffective group. The area under curve (AUC) of ⊿SUV_max2% (0.876) > AUC of ⊿SUV_max1% (0.756) > AUC of ⊿MTV₂₂% (0.740). In the tumor diameter < 2.5cm group, there were statistically significant differences between ⊿MTV₁₂% when SUV=1.5 as the boundary (p=0.033) in effective group and ineffective group. The area under curve (AUC) of ⊿SUV_max2% (0.969) > AUC of ⊿SUV_max1% (0.854) > AUC of ⊿MTV₁₂% (0.781).

Conclusions MTV can predict pathological response of breast cancer to NAC, but ⊿MTV% don’t have advantages in prediction evaluation of NAC in breast cancer compared to ⊿SUV_max%.