Intramedullary rod failure in metastatic breast cancer: Do triple negative cancer patients have more revision surgery?

BACKGROUND: Breast cancer is the most common cancer and second cause of death in women worldwide. Patients with breast cancer are classified into subgroups based on the presence or absence of hormone receptors and the human epidermal growth factor 2-neu (HER-2) marker, the different molecular profiles come with an associated prognosis and variety of possible treatment options. Patients with triple negative cancer have a worse prognosis, a more aggressive behavior, higher likelihood of spreading, a higher risk of recurrence and a poorer outcome overall. Intramedullary rod fixation has proven to provide a good outcome and function in patients with metastatic breast cancer, but no study has addressed the receptor-status potential outcome differences that may affect disease progression at an orthopaedic surgery site. QUESTIONS/PURPOSES: (1) Do patients with triple negative breast cancer have a higher revision rate of intramedullary rod fixation of bone metastases? (2) Do patients with metastatic triple negative breast cancer have a higher revision rate of intramedullary rod fixation due to local disease progression? METHODS: This was a single-center, observational, retrospective cohort study. Fifty-seven patients with a diagnosis of breast cancer metastatic to long bones who underwent surgical fixation with an intramedullary rod for a pathological fracture or an impending fracture due to a bone metastasis with a Mirels’ score equal or above 8 between January 2004 and December 2016 at our institution were included. All implants used were from the same manufacturer (Stryker Corp., Mahwah, NJ, USA). Patients were divided into two groups based on the receptor status of the tumor and were classified either as triple negative, when the tumor lacked progesterone, estrogen and HER-2 receptors, or as receptor-positive when the presence of one or a combination of either three was proven. In the triple-negative tumor group the mean follow up time was 26 months (SD 29) and median follow up time was 16 months. In the receptor-positive tumor group mean follow up was 27 months (SD 24) with a median follow up of 19 months. To assess possible associations between different factors and the outcomes of interest, we used either the chi-square test or Fisher’s exact test for categorical variables and the ANOVA test for continuous variables. For the survival assessment, a Kaplan-Meier analysis was performed and for the cumulative incidence a competing risk analysis was utilized. RESULTS: The intramedullary rod revision rate for patients in the triple-negative tumor group was 17%, while for the receptor-positive group it was 12%, this was not statistically different for our sample size. The mean time for revision of the intramedullary rod in the whole sample was 19 months (SD 11, range 6–40). The causes of revision were disease progression (43%), nonunion (29%) and surgeon error (29%). The cumulative incidence of revision surgery was 6% (CI 95%, 2–14%) at 12 months and 20% (CI 95%, 8–36%) at 60 months. CONCLUSIONS: Intramedullary rodding can be considered for the treatment of long bones metastases in breast cancer patients for an impending or actual pathological fracture. There is no difference in the intramedullary rod revision rate among patients with different receptor-status when comparing triple-negative tumor patients and receptor-positive ones. LEVEL OF EVIDENCE: Level III, therapeutic study.