Patterns of progression in bone and soft tissue following treatment with Ra-223 in metastatic castrate resistant prostate cancer (mCRPC).

Abstract

222 Background: Bone scans were not obtained in the phase 3 ALSYMPCA trial, and retrospective series have reported varying rates of development of new lesions and resolution of existing lesions, following treatment with Radium-223 (Ra-223). Methods: We performed a retrospective chart review of all men with mCRPC who received at least one dose of Ra-223 at Duke Cancer Institute from June 1, 2013 to June 1, 2015, in order to specifically describe radiographic changes on bone scan and CT during and following treatment. Radionuclide bone scans were reviewed by two radiologists prior to, during, and following Ra-223 treatment. The automated bone scan index (aBSI) was generated at each time point using EXINI boneBSI v. 2. Results: We identified 61 men with mCRPC (72% white, 28% black, median age 70) who received ≥ 1 dose of Ra-223 (median 5 doses, range 1-6). Prior treatments included: abiraterone (71%), enzalutamide (71%), sipuleucel-T (59%), docetaxel (56%), and cabazitaxel (18%). At baseline, 46% of men had nodal metastases, 3% had liver metastases, and 3% had lung metastases. Post-treatment bone scans demonstrated 0, 1-4, 5-9, 10-20, and > 20 new bone lesions in 15%, 10%, 8%, 8%, and 18%, respectively; 10% had resolution of 1-4 bone lesions. Median aBSI was 2.56 at baseline and 3.07 post-treatment. Progression in soft tissue included lymph node (31%), liver (23%), lung (5%), and epidural (8%). Of men with available imaging during treatment, 10 of 14 (71%) had new lesions on bone scan, 15 of 27 (56%) progressed on CT, and 3 of 14 (21%) progressed on both bone scan and CT; these proportions were 44%, 16%, and 24% following treatment, respectively. Men with prior chemotherapy (n = 33) had higher rates of progression on CT during (73%) and after treatment (40%), compared to men with no prior chemotherapy (36% and 25%, respectively). Conclusions: In a heavily treated population of men with mCRPC, radiographic progression in bone and/or soft tissue is common during and shortly after completion of Ra-223 treatment. Patients with prior chemotherapy have higher rates of non-bone progression, compared to patients with no prior chemotherapy. Bone scan and CT imaging are recommended during and after Ra-223.