Utility of bone scintigraphy during the course of radium-223 treatment in mCRPC patients

Ziel/Aim Only a few studies describe imaging response to radium-223 (Ra-223) treatment by evaluating bone scintigraphy, particularly with respect to therapy associated flare. We evaluated the value of Tc-99 m-DPD bone scintigraphy during the course of radium-treatment in a single center.

Methodik/Methods A total of 113 mCRPC patients were included in this retrospective analysis of whom 33  % (n = 37/113) received one to four injections (Gr. A) and 67  % (n = 76/113) five to six injections (Gr. B). Laboratory parameters including differential blood count, PSA, ALP and LDH were noted. Bone scan was performed in all patients prior to Ra-223 and was available in 72 patients after 3 injections and in 64 patients 8 weeks after the sixth Ra-223 injection. Bone scans were evaluated using an automated BSI software (EXINI) and calculation of total tumor burden in SPECT, if available.

Ergebnisse/Results In Gr. A eight patients received bone imaging after three injections, remaining patients stopped Ra-223 treatment prior to interim staging due to clinical disease progression. Five patients (62,5  %) showed increasing uptake pattern in bone scan. In these patients mean PSA increased from 10,60 ng/ml at baseline to 111,65 ng/ml (+ 953,30  %), whereas AP decreased from 117,0 U/l to 89 U/l (−23,93  %). In Gr. B interim staging was performed in 45 patients (59  %). 12 patients (27  %) presented increasing uptake pattern in bone scan, whereas 33 patients (73  %) showed treatment response with decreasing tracer uptake. In Gr. B PSA moderately increased from 25,95 ng/ml at baseline to 27,9 ng/ml (+ 7,51  %), AP deceased from 100 U/l to 75 U/l (−25  %), LDH slightly decreased from 253,0 U/l baseline to 238,5 U/l (−5,73  %). Bone scan after six Ra-223 injections was available in 61 patients (90  %) with 15 (25  %) presenting increasing tracer uptake and 46 (75  %) treatment response. PSA decreased by 39,11  %, AP by 29  % and LDH by 4,55  %.

Schlussfolgerungen/Conclusions Despite the occurrence of flare phenomenon bone scintigraphy can be used to identify patients profiting from Ra-223 treatment even after three injections and could be used to predict treatment response. A correlation of imaging results and patient’s survival is currently being performed.