Early prediction of response to neoadjuvant chemotherapy in breast cancer patients: comparison of single-voxel ¹H-magnetic resonance spectroscopy and ¹⁸F-fluorodeoxyglucose positron emission tomography

Objectives: To prospectively compare performances of single-voxel proton magnetic resonance spectroscopy (¹H-MRS) and ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in predicting pathologic response to neoadjuvant chemotherapy (NAC) in breast cancer patients. Methods: Thirty-five breast cancer patients who received NAC and subsequent surgery were prospectively enrolled. MRS and FDG-PET were performed before and after the 1st NAC cycle. Percentage changes of total choline-containing compounds (tCho) via MRS, and maximum and peak standardized uptake values (SUV_max, SUV_peak) and total lesion glycolysis (TLG) via FDG-PET were measured, and their performances in predicting pathologic complete response (pCR) were compared. Results: Of the 35 patients, 6 showed pCR and 29 showed non-pCR. Mean % reductions of tCho, SUV_max, SUV_peak, and TLG of the pCR group were larger than those of the non-pCR group (-80.3 ± 13.9 % vs. -32.1 ± 49.4 %, P = 0.025; -54.7 ± 22.1 % vs. -26.3 ± 33.7 %, P = 0.058; -60.7 ± 18.3 % vs. -32.3 ± 23.3 %, P = 0.009; -89.5 ± 8.5 % vs. -52.6 ± 36.2 %, P = 0.020). Diagnostic accuracy (area under ROC curve; Az, 0.911) of the % reduction of tCho was comparable to those of %SUV_max (0.822), SUV_peak (0.862), and TLG (0.879) in distinguishing pCR from non-pCR (all P > 0.05). Conclusion: MRS showed comparable performance to FDG-PET in early prediction of pCR in breast cancer patients. Key points: • MRS can predict response to NAC in breast cancer post-1^stcycle. • Changes in tCho and SUV after NAC reflect tumour cellularity changes. • MRS can be an alternative to FDG-PET in predicting response to NAC.