RETROSPECTIVE ANALYSIS OF XOFIGO TREATMENTS

2041 Introduction: Radium-223 dichloride is a relatively new radionuclide therapy for patients with castrate resistant prostate cancer (CRPC) metastatic to bone. This alpha emitter offers palliation of pain and extends life by 3.6 months per the ALSYMPCA trial’s updated analysis, but is a lengthy treatment course (up to 6 months) and is significantly more expensive than its purely palliative counterparts such as Sm-153 EDTMP. Objectives: Analyze patient data to determine: • If patients are being referred for radium therapy too late in the course of disease • Frequency and causes of incomplete treatment plans • If alkaline phosphatase (ALP) is a better indicator of treatment response than prostate specific antigen (PSA). Methods: Retrospective chart review of all patients in the Kaiser Permanente Northern California Region who underwent treatment with radium-223 dichloride between 10/2013 and 4/2018. Data included patient’s age, date of initial prostate cancer diagnosis, date of prostate cancer recurrence, Gleason score, number and date of completed radium-223 dichloride injections, lab parameters (CBC, PSA and ALP) before, during, and after treatment, and reason(s) for discontinuation of treatment before completion (if applicable). Results: A total of 67 patients (average age 73 years) received at least 1 treatment with radium-223 dichloride between 10/2013 and 4/2018. 30 (45%) patients completed the entire 6-dose regimen. 37 (55%) patients did not complete all 6 injections (mean number of received injections was 3): reasons for treatment discontinuation included patient death (37.8%), rising PSA levels (29.7%), bone marrow suppression (13.5%), worsening pain (8.1%), development of visceral metastases (5.4%) and clinician or patient choice (5.4%). Of those who died during treatment, the mean number of received injections was 2.7, with 5 patients only receiving 1 injection and 2 patients only receiving 2 injections. Out of all 67 patients, 41 had more than 3 injections and lab values for both consistent PSA and ALP throughout treatment. 7 of these patients had declining PSA, while 30 had declining ALP. Conclusions: Less than half of the patients in this study completed the full series of 6 injections, with patient death being the leading cause for premature termination of treatment. Furthermore, half the patients that died during treatment received 2 injections or less. These findings suggests that referrals for this treatment may be coming too late in the course of the patient’s disease course. Rising PSA levels was the second most common cause for treatment discontinuation. In patients who had both PSA and ALP levels monitored during treatment, PSA remained stable or increased in 83% of the patients who completed 3 or more injections while 73% had decreasing ALP levels. This suggests that ALP levels could potentially be a better marker of treatment response than PSA; however, no definitive conclusion can be drawn due to small size of this study. These findings are of relevance because the clinical (survival, etc.) benefit of less than 6 injections has not been established, and incomplete treatment could potentially lead to more harm than benefit.