Response Prediction to Neoadjuvnat Chemotherapy in Locally Advanced Breast Cancer with Scintimammography

Objectives: To measure Retention index (RI) at 120 minutes through scintimammography technique and to determine its relationship with mammographic results and Multi Drug Resistant-1 Messenger Ribonucleic Acid (MDR-1 mRNA) expression. Place and Duration: Data collected at Nuclear Medicine Department of Nuclear Medicine, Oncology and Radiotherapy Institute (NORI), Islamabad for 6 months (February to August 2012) Study Design: Prospective cross-sectional study. Material and Methods: 20 patients with locally advanced breast cancer, candidates for NACT with no previous history of mastectomy or chemotherapy were included. All underwent mammograms of the diseased breast before and after NACT to measure the size of the lesion according to the response evaluation criteria in solid tumors (RECIST). All the patients then underwent scintimammography with 740 MBq Technetium 99m Sestamibi (Tc- 99m-MIBI). Two sets of images acquired at 15 and 120 minutes after the injection of Tc-99m- MIBI. RI as a fraction of initial uptake (15 min) at 120 min was calculated. MDR-1 mRNA levels of all patients were measured with Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) method. The patients then underwent three cycles of anthracycline based NACT. The patients with 30% reduction in tumor size on final mammographic image were labeled as responders (R) and rest as non-responders (NR) to NACT. Results: The results showed 11 (55%) responders and 9 (45%) non responders. RI at 120 min showed significant association with mammographic results and MDR-1 mRNA expression (P 0.05). Conclusions: Response to neo-adjuvant chemotherapy for LABC can be predicted by scintimammography as it is linked with high retention index (P=0.017) and weak MDR-1 mRNA expression (P=0.018).