Abstract P6-15-05: Demographics and survival in metastatic inflammatory breast cancer. SEER data analysis

Abstract

Abstract Background: Inflammatory breast cancer (IBC) is a rare and aggressive malignancy, distinguished by characteristic skin changes with/without breast mass. While new therapies have improved the survival of IBC, the prognosis of metastatic disease (stage IV) remains poorly described. The current analysis is aimed at investigating the demographics of metastatic IBC and the impact of chemotherapy use and tumor subtype on survival. Methods: Using ICD-O-3 histology code 8530/3 in the Surveillance Epidemiology and End Results database (SEER), demographics and survival data on metastatic IBC diagnosed between 2010 and 2015 were abstracted. JMP 14 statistical software was used for data analysis. The SEER database does not record specific age above 85 years and these cases were excluded. Results: Over five years, 378 patients were diagnosed with metastatic IBC. All were women and most were Caucasian (282, 75%). Mean age was 60±14 years. During the observation period 284 (75%) patients died and of which 218 deaths were attributable to IBC. Cancer subtype was unknown in 61 patients; for the rest, Luminal A was the most common (121, 38%), followed by triple negative (74, 23%), HER2 enriched (62, 20%) and luminal B (60, 19%). Median overall survival (OS) was 18 months (95% CI 14-20), with a survival rate of 39% at 24 months from diagnosis. In unadjusted analyses, patients receiving chemotherapy (n=191) had increased survival at every time point compared to those who did not (n=93), (median OS 22 (95% CI 18-26) vs 5 months (95% CI 2-11), p<0.0001; 24 month survival rate 46% vs 22%). Stratification by cancer subtype showed worst median OS for triple negative breast cancer (11 months, 95% CI 6-13), similar survival for HER2 enriched and luminal A (20 [95% CI 17-29] and 22 [95% CI 17-34] months, respectively) and best OS for luminal B (42 months [95% CI 26-61]). These differences were statistically significant (log rank p<0.0001). A proportional hazards model including age, ethnicity, tumor subtype and treatment identified Caucasian race (HR 0.72 [95% CI 0.53-0.98], p=0.03) and use of chemotherapy (HR 0.49 [95% CI 0.34-0.71], p=0.0002) as predictors of improved survival. Patients with tumor subtype Luminal B had the best OS; by comparison, Luminal A (HR 1.43 [95% CI 0.94-2.22], p=0.09), HER2 enriched (HR 1.7 [95% CI 1.06-2.7], p=0.02) and triple negative breast cancer (HR 3.7 [95% CI 2.4-5.8], p<0.0001) had excess mortality. Interestingly, increasing age at diagnosis was not significantly associated with a poor prognosis (HR 1.007 [95% CI 99.7-1.01], p=0.18). Conclusion: From our data, IBC is common in Caucasian women in their 7th decade of life. Luminal B was the least common cancer subtype and had the best overall survival. Chemotherapy appears to play an important part in increasing survival; but ethnicity and tumor subtype are also important predictors of mortality. Keywords: Inflammatory breast cancer, Metastatic, Survival, Demographics Citation Format: Nwabundo Anusim, Filip Ionescu, John Khoury, Anish Konde, Ishmael Jaiyesimi. Demographics and survival in metastatic inflammatory breast cancer. SEER data analysis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-15-05.