Abstract P1-16-05: Incidence of skeletal-related events in patients suffering of bone metastsis from breast cancer treated with bisphosphonates or denosumab

Abstract

Abstract Background Bone is a frequent site of metastases and typically indicates a short-term prognosis in breast cancer patients. Bone metastasis can rarely be cured, but often it can still be treated to slow down its growth and to improve quality of life. The relative incidence of bone metastases in patients with advanced metastatic breast cancer is 65-75%. Bisphosphonates and the human monoclonal RANKL-antibody Denosumab are the most common medical treatment of bone metastasis. Therefore we investigated their effect on skeletal-related events (SRE) in our patient collective. Materials and methods: A retrospective analysis of 143 patients with histologically proven breast cancer and bone metastasis at the department of Gynaecology and Obstetrics at the University of Saarland (Germany) between October 2009 and October 2013. SREs were defined as a pathological fracture, a bone surgery, a spinal cord compression and a radiation of bone metastasis. Patients were distributed into 5 different groups according to the treatment received. Group 1: bisphosphonate (n=63), Group 2: denosumab (n=55), Group 3: bisphosphonate switch to denosumab (n=16), Group 4: denosumab switch to bisphosphonate (n=4), Group 5: no anti-resorptive therapy (n=5). Progression of the bone metastasis without skeletal-related event (SRE) was defined as progressive disease. Results: At the time of diagnosis of the breast cancer the average age was of 55,2±13,1 years. At the time of data collection n=53 patients were alive, n= 83 had died during follow up, and n= 7 were lost-of follow up. The median follow up from the first diagnosis of the primary breast cancer and the end of data collection was of 88,6 ± 78,5 month. In 103 (72%) patients bone metastases were detected secondarily. 83 patients recieved an anti-resorptive therapy with bisphosphonates (q4w), 75 patients were treated with denosumab (q4w). In the overall collective, an SRE occured in 95 patients. 65.1% of Group 1(bisphosphonate) and 65.5% of Group 2 (densosumab) patients sufferd from an SRE. In the non-treatment Group 2, 5 patients were diagnosed with SRE. The Switch groups showed the most frequent SREs (Group 3: 81,3%), (Group 4: 75,0%) the median duration of treatment prior to the first SRE was 12,33 month in Group 1, 1,5 month in group 2, 38,2 month in Group 3 and 4 month in group 4. 63 of 95 patients received a treatment modification after the first SRE. The time period between the first and second SRE was 31,8 month in Group 1, 10,38 month in group 2, 38.71 month in group 3, 10 month in group 4 and 3 month in group 5. 3,5% of all patients in the overall collective were diagnosed with an osteonecrosis of the Jaw. Conclusion This data suggests that the anti-resorptive therapy with densoumab is equal to the bisphosphonate therapy to prevent the first skeletal-related event in patients with bone metastasis of breast cancer. After the first SRE patients benefit significantly of an anti-resorptive therapy compared to no treatment. In our population the prevention of a second SRE in group 3 (bisphosphonate switch to denosumab)showed the best results. Citation Format: von Heesen A, Nilges K, Radosa J, Gabriel L, Solomayer E-F, Juhasz-Böss I. Incidence of skeletal-related events in patients suffering of bone metastsis from breast cancer treated with bisphosphonates or denosumab [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-16-05.