Predictors and prognostic implication of pathologic fracture (PF), spinal cord compression (SCC), and bone surgery (BS) following diagnosis of metastatic prostate cancer (PCa).

Abstract

133 Background: Information is limited about the predictors of PF, SCC, or BS and their relationship with PCa mortality in older men diagnosed with metastatic PCa. Methods: We analyzed patients aged 66 or older from the linked Surveillance, Epidemiology, and End Results & Medicare (SEER-Medicare) database. Cases were diagnosed with M1 PCa between 2000 and 2007. Patients surviving at least 30 days post-diagnosis were identified and followed until death or censoring in December, 2009. Post-diagnosis occurrence of PF, SCC, and BS was identified using Medicare claims. (Multinomial) logistic and Cox proportional hazards regression models controlled for demographic characteristics, preventive service use, comorbidity status, and performance status proxies. Survival models were estimated in the full sample (FS) and in a propensity-score matched sample (PSMS). The survival requirement was relaxed and patients diagnosed with stage M1b were considered in sensitivity analyses. Results: Application of inclusion criteria resulted in 7,062 patients in FS (2,398 in PSMS). PCa-specific and all-cause mortality were 54% and 80% at a median (mean; min; max) follow up of 609 days (837; 30; 3,653). The average age for the sample was 78 yrs and 14% were non-Hispanic African American. The proportion with any event, SCC, PF, and BS were: 17%; 10%; 5%; 3%. Race, marital status, comorbid conditions, and health services use related to bone metastases were correlated with the likelihood of sustaining a PF, SCC, or BS, with differences based on the type of event. In the PCa mortality model the HR associated with each event was as follows using FS: [SCC] HR 1.12, 1.01 – 1.24; [PF] HR 1.14, 1.00 – 1.31; [BS] 0.61, 0.50 – 0.75. Results using PSMS were: [SCC] HR 1.04, 0.92 – 1.17; [PF] HR 1.11, 0.96 – 1.28; [BS] 0.58, 0.47 – 0.72. Relaxing the assumption of a minimum survival requirement did not change qualitative results. Conclusions: Patient demographics and clinical comorbid conditions correlate with the likelihood of sustaining PF, SCC or BS. Compared to fractures and spinal cord compression, the relationship between bone surgery and PCa-specific survival is more favorable.