Abstract 668P
Background
Radium-223 (Ra-223) improves overall survival (OS) in men with mCRPC with predominantly bone metastases. Apart from the presence of bone only metastases, no validated prognostic clinical factors are widely used to select patients for treatment with Ra-223.
Methods
We conducted a retrospective study of men with mCRPC treated with Ra-223 at the Princess Margaret Cancer Centre. Clinical and disease characteristics were reviewed. OS was estimated by the Kaplan-Meier method. Uni- (UVA) and multi-variate (MVA) analyses (Cox-regression) were used to evaluate potential prognostic factors.
Results
Between May 2015 and July 2018, 150 men received Ra-223. The median age was 74 years (52-93), and the median number of doses received was 6 (94 [62.7%] received >4 doses, 56 [37.3%] received ≤4 doses). 58% had 6-20 bone metastases and 28% had > 20. The following baseline factors had a median (range) of: ECOG 1 (0-3), ALP 110 U/L (35-1633), Hb 120 g/L (69-160), PSA 49 ug/L (0.83-7238), LDH 230 U/L (82-1426), Albumin (ALB) 39 g/L (24-47), PSADT 2.4 months (-27-218). The median OS for the overall cohort was 14.5 months (95% CI: 11.2-18). UVA and MVA results are presented in the table. A prognostic index model based on the MVA, which assigned 1 point for each factor (ECOG 2-3, PSA>80 ug/L, ALP >150 U/L, ALB <35 g/L), identified three distinct prognostic groups. Median OS for the good risk (≤1 factor) (n=103), intermediate risk (2 factors) (n=30), and poor risk (≥3 factors) (n=17) was 19.4 (95% CI 17.4-21.8), 10.0 (95% CI 6.1-13.9), and 3.1 months (95% CI 1.2-5.1), respectively (P<0.001). Table: 668P
| Baseline Factor | UVA | MVA | ||
| HR (95% CI) | P value | HR (95% CI) | P value | |
| ALB <35 g/L | 2.5 (1.6-4.0) | <0.001 | 2.0 (1.2-3.2) | 0.005 |
| ALP > 150 U/L | 2.2 (1.6-3.3) | <0.001 | 1.8 (1.3-2.7) | 0.002 |
| ECOG (2-3) | 2.4 (1.5-4.0) | <0.001 | 3.0 (2.0-4.7) | <0.001 |
| Hb < 120 g/L | 2.0 (1.4-2.9) | <0.001 | 1.5 (1.0-2.2) | 0.052 |
| LDH > 220 U/L | 1.8 (1.3-2.6) | 0.001 | 1.4 (0.9-2.0) | 0.102 |
| PSA > 80 ug/L | 2.0 (1.5-3.0) | <0.001 | 1.7 (1.2-2.5) | 0.006 |
| PSADT< 3months | 1.5 (1.0-2.2) | 0.026 | 1.3 (0.9-1.8) | 0.22 |
Conclusions
Baseline ECOG, ALP, PSA and ALB were independently associated with OS and could be used to identify patients most likely to benefit from Ra-223. Validation in an independent dataset should be encouraged.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Aaron Hansen.
Funding
Has not received any funding.
Disclosure
A. Sacher: Honoraria (institution), Advisory/Consultancy: AstraZeneca; Honoraria (institution), Advisory/Consultancy: Bayer; Honoraria (institution): Genentech-Roche; Honoraria (institution): Merck. A. Zlotta: Advisory/Consultancy: Sanofi; Advisory/Consultancy: Ferring; Advisory/Consultancy: Janssen. A. Hansen: Advisory/Consultancy, Research grant/Funding (institution): Genentech/Roche; Advisory/Consultancy, Research grant/Funding (self): Merck; Advisory/Consultancy, Research grant/Funding (self): Boston Biomedical; Advisory/Consultancy, Research grant/Funding (self): GSK; Advisory/Consultancy, Research grant/Funding (institution): BoehringerIngelheim; Advisory/Consultancy, Research grant/Funding (institution): AstraZeneca; Advisory/Consultancy, Research grant/Funding (institution): Medimmune; Advisory/Consultancy, Research grant/Funding (institution): Bristol-Myers Squibb; Advisory/Consultancy, Research grant/Funding (institution): Novartis. All other authors have declared no conflicts of interest.