Response of malignant breast tumours to neoadjuvant chemotherapy evaluated with Tc-99m MIBI

The aim of this study was to assess the efficacy of Tc-99m sestamibi scintimammography in the prediction and evaluation of tumour response to neoadjuvant chemotherapy in patients with locally advanced breast cancer.

The subjects consisted of 14 female patients with unilateral locally advanced breast cancer eligible for anthracycline-based neoadjuvant chemotherapy followed by surgery. The patients underwent mastectomies with pathologic evaluation of the residual tumour size. The early and delayed static imaging were undertaken in all subjects at 10 and 120 minutes after intravenous injection with 720-1080 MBq of Tc-99m MIBI. Patients lay prone on the scintimammographic pad (provided by the IAEA). The acquisition included three positions: both lateral prone and anterior supine. Early, delayed tumour to background ratios (TBR) and washout rate (WOR) were calculated. Three sets of scintimammography images were obtained: baseline study (BL), the first follow-up study (FF) after two cycles of chemotherapy and the second follow-up (SF) scan on completion of chemotherapy and prior to surgery. Clinical response was evaluated following WHO criteria and classified as complete response (CR), partial response (PR), stable disease (StD) and progressive disease (PD). All patients underwent BS, seven of them FF and eight completed the study with SF.

The only statistically significant differences in Student's t-test for matched pairs were found between mean values of TBR10 and TBR120 in BL and FF study however in the SF study it was not significant. Other differences between the mean values of TBR10, TBR120 and WOR in BL/FF, BL/SF and FF/SF studies were not statistically significant.

The results obtained are encouraging, but further investigations are needed.