99mTc-MIBI SPECT/CT in Breast Malignancy

Overview

99mTc-SestaMIBI mammoscintigraphy (MMS) may be used in patients with locally advanced breast cancer (LABC) scheduled for neoadjuvant chemotherapy. MMS may be performed for 1) nodal staging of axillary lymph node metastases, 2) prediction of chemosensitivity or Pgp/MDR-1 mediated chemoresistance, and 3) evaluation of efficacy to chemotherapy and radiation therapy. MMS is routinely performed with planar/SPECT imaging according to the Society of Nuclear Medicine and European Association of Nuclear Medicine guidelines. In this pilot study, an optimised acquisition protocol will be setup with SPECT/low-dose multislice CT in addition to planar imaging.

99mTc-SestaMIBI is a lipophylic cation as many cytotoxic chemotherapy drugs (i.e. anthracyclines, inhibitor of topoisomerase II, antimicrotubule, vinca alkaloids, inhibitors of DNA replication) accumulating in the mitochondria of tumour cells. MIBI tumour uptake is related to viability and proliferation due to increased perfusion and increased energy-dependent metabolism. 99mTc-SestaMIBI is a substrate for the glycoprotein P (Pgp) pump encoded by the multidrug resistance gene -1 (MDR-1). MIBI tumour uptake with no significant wash-out over time (\<45% at 3H) predicts a chemosensitivity with no Pgp/MDR-1 overexpression. MIBI efflux with no significant tumour uptake predicts efflux of chemotherapy drugs from the tumour cells related to Pgp/MDR-1 overexpression or to anti-apoptotic Bcl-2 overexpression. Early MIBI efflux (\< 1H) may also be related to pro-apoptotic Bax overexpression. SPECT/CT will be used for anatomic localisation and and attenuation correction. CT from SPECT/CT is a low-dose (\< 2 mSv) multislice CT (4 slice). SPECT/CT will also be used for correction of image-degrading factors including collimator-detector-response compensation for resolution recovery, and scatter correction. SPECT/CT based absolute semi-quantification of MIBI uptake into primary tumour and lymph nodes (i.e. standardised uptake value or SUV) will also be performed. SPECT/CT optimised imaging will be compared to planar/SPECT conventional nuclear imaging for 1) detection of MIBI-avid primary breast tumour and lymph node metastases, 2) semi-quantification of MIBI uptake (T/B, SUV, and %wash-out) into primary breast tumour and lymph node metastases, 3) prediction of chemosensitivity at baseline, 3) Evaluation of chemotherapy efficacy after the first course of chemotherapy (after 2 weeks) compared to clinical response and histo-pathological response. SPECT/CT mammoscintigraphy findings will be compared to clinical findings (palpation), radiological findings (mammography, US, MRI), and histo-pathological findings (Pgp/MDR-1 expression) into tumours after surgery.