Changes of Skeletal Metastases on Imaging Post Treatment with Radium-223

Objectives To evaluate imaging response of skeletal metastases in patients with castrate resistant prostate cancer treated with radium-223 chloride.

Methods 9 consenting patients were recruited locally for the international multicenter randomized control trial ALSYMPCA. Bone scans and/or MR spine had been acquired at trial baseline for all patients. In the 6 patients who completed all trial treatments, standard of care follow-up imaging was performed within 5 months. Pre- and post-treatment bone scans for 5 patients were retrospectively analyzed; studies were blinded with respect to whether radium-223 or placebo was given, dates removed and order of each study pair randomized, and independently read by one senior and two junior nuclear medicine physicians. Pre- and post-MR spine for one patient where a post-treatment bone scan was not available was evaluated by a board certified radiologist. Changes with each scan pair were assessed as stable, progressed, improved, or mixed response.

Results One control patient who received placebo was assessed as either progression or mixed response on bone scan. Out of 5 patients who received radium-223, bone scan was assessed as improved by all readers in one patient, a mixed response by all readers in one patient, progression or stability in one patient, and no agreement on response in one patient; one patient progressed on MR.

Conclusions There is variability in the short term imaging appearance of skeletal metastases following treatment with radium-223. Improvement can be observed, which warrants further larger scale prospective investigation to evaluate usefulness in predicting clinical response.