TECHNITIUM-99m-SESTAMIBI SCANNING (MIBI) CORRELATES WITH DISEASE ACTIVITY IN PATIENTS (PTS) WITH MULTIPLE MYELOMA UNDERGOING AUTOLOGOUS PERIPHERAL BLOOD STEM CELL TRANSPLANTATION (PBSCT).

Traditional radiographs are often used to establish a diagnosis of MM, as over 80% of patients will have some form of bone disease, including osteolysis and osteopenia. However, radiographs offer incomplete and sometimes misleading information regarding an individual patient’s progress. Pace et al (Eur J Nuc Med, 1998) initially reported the use of MIBI scans to examine bone disease in pts with MM. We hypothesized that MIBI scans could provide a convenient, reproducible method to track pts with MM. We therefore investigated the ability of MIBI scans, in comparison with radiographs and dual energy x-ray absorptiometry (DEXA) to diagnose and follow MM disease progression, as assessed by clinical criteria.

Methods: Patients were subjects enrolled in an autologous PBSCT protocol using escalating doses of busulfan and melphalan. Pts received a complete bone survey, DEXA scanning and MIBI scanning prior to PBSCT. Pts able to return for follow up received all 3 tests at various time intervals. MIBI scans consisted of the injection of 30 mCi of technietium-99m-sestamibi followed by immediate scanning with a dual headed gamma camera to produce whole body images. Spot films were made of areas of increased activity. Two radiologists blinded to clinical outcomes reviewed and scored the MIBI films based on scan intensity rated as 0–4 in each of five areas. Scores were averaged, then summed and reported as a total score for each pt. Interrater reliability was determined by using Cohen’s kappa statistic.

Results: 31 pts were enrolled on the PBSCT protocol, with 29 pts receiving baseline MIBI scanning. The initial total MIBI scores ranged from 2.5 to 16.5 with a mean score of 11 out of a possible 20. Of note, pts categorized as having either a complete remission (CR) or near complete remission (nCR) (n=4, mean score 6.1) had significantly lower (p=.02) MIBI scores in comparison to pts graded as either stable or progressive disease (n=12, mean score 11.5) prior to PBSCT . Eleven pts had serial scans performed at intervals of 6 to 12 months. Of these, 6 pts with stable/progressive disease had pre PBSCT MIBI scores ranging from 9 to 16.5 with a median score of 12. The single pt with nCR had a MIBI score of 5.5. At the first follow up, pts in stable/PD group had MIBI scores that significantly improved, ranging from 1.5 to 5.5 (median=3.3) with concomitant laboratory and marrow improvement (near CR-3, PR-3) but no change in their xray or DEXA scans. The pt with a nCR also showed improvement in protein and marrow findings to a CR with follow up MIBI score of 1.5. Two of 11 pts classified before PBSCT as "non secretory" MM with negative bone marrow biopsies had prePBSCT MIBI scores of 10.5 and 12, which improved post PBSCT to 3 and 6, respectively and corresponded to subjective improvement in bone pain and anemia. With median follow up of 30 mos for these 11 patients, 2 pts have relapsed by standard criteria, with corresponding increase in MIBI score, but no new lytic lesions documented by radiographs or DEXA.

Conclusions: Technitium-99m-sestamibi scans provide a simple, inexpensive method (average cost per MIBI $175) to follow the clinical course of MM patients, especially those with nonsecretory disease, and may prove more cost effective and accurate than other imaging methods for tracking total disease burden. We believe that further investigation of MIBI scanning for this indication is warranted.