The incidence and risk factors predictive of bone metastases at initial diagnosis of malignancy.

e18816 Background: Bone metastases are associated with increased morbidity and decreased quality of life in patients with solid tumors. We report here the incidence and predictive factors for bone metastases at initial diagnosis in a large population-based dataset. Methods: The Surveillance, Epidemiology, and End Results (SEER) database was used to identify patients 18 years-old or older and with solid cancers of all stages diagnosed from 2010 to 2019. We calculated the incidence and predictive factors for bone metastases according to demographic and tumor characteristics. Results: Among the 1,132,154 patients identified, 1,075,069 (94.96%) had known bone metastasis status and were eligible for the study. Bone metastases were detected in 55,903 (4.9%) patients. Among patients with bone metastases, the most common primary tumors were lung (44.4%), prostate (19.3%), breast (12.4%), kidney (4.0%), colorectal (2.24%) and pancreas (2.23%). The percentage of bone metastases in patients with non-small cell lung cancer (NSCLC), prostate adenocarcinoma, infiltrating ductal carcinoma of the breast (IDC), and colorectal adenocarcinoma (CRC) was 18.04% (18,123 out of 100,447), 5.92% (9,071 out of 153,325), 2.9% (4,490 out of 154,626), and 1.17% (1,043 out of 89,510) respectively. In addition to T and N stage, independent risk factors by multivariable analysis for bone metastases included female sex and non-squamous histology in NSCLC, black race, hormonal and HER2 status in breast cancer, Gleason score and PSA in prostate cancer, male sex, black race, rectal location, liver metastases and lung metastases in CRC. In univariate analysis, the strongest predictors for bone metastases were N2/3 (28.3%) and T3/4 (24.9%) in NSCLC, T3/4 (15.8%), N2/3 (10.6%), N1 (5.9%) and HER2 positive (4.9%) in IDC, N1 (38.1%), Gleason score 9/10 (22.8%), PSA 98 or higher (19.5%) and PSA 20-97 (16.8%) in prostate cancer, and rectal or rectosigmoid location (1.43% vs 1.05% in colon cancer, p < 0.001) in CRC. Conclusions: Approximately 5% of patients with solid tumors have bone metastases at presentation. In addition to T and N stage, there are several risk factors for bone metastases according to the primary tumor site.