Background: Breast cancer (BC) is the most diagnosed cancer and the leading cause of cancer death among women in Puerto Rico (PR). Inflammatory breast cancer (IBC) is considered the most aggressive BC subtype. This study characterized the IBC population of Hispanic women living in Puerto Rico and aimed to estimate the IBC survival rate using data from the Puerto Rico Central Cancer Registry (PRCCR). Methods: This is a retrospective, population-based study using the PRCCR database and the Health Insurance Linkage Database (PRCCR-HILD). We analyzed data from patients that were diagnosed with IBC from January 1, 2008 to December 31, 2018. Patients were identified using the International Classification of Diseases for Oncology, 3rd edition (ICD-O-3) site codes C50.0-C50.9 and histology code 8530. Variables such as age at diagnosis, marital status, health insurance, geographic area of residence, staging variables, tumor receptor subtypes, treatment received, and overall survival (OS) were studied. Statistical analysis methods were employed to describe the population, estimate survival curves and examine the risk of dying. Results: The data of 51 patients were included. The mean age at diagnosis of IBC in the current study was 59 years old. A total of 62.8% of patients had no metastases at diagnosis and 64.7% were diagnosed with stage III disease. Most tumors presented with ER+/PR+/Her2-(21.6%), or a triple negative (ER-/PR-/Her2-, 15.7%) tumor concordance. The OS during the first year was 66% (90% CI: 0.54-0.76), whereas 36 months post-diagnosis was at a low 39% (90% CI: 0.27-0.59). The triple-negative subtype had the worst survival at 36 months (36% [90% CI: 0.11-0.62]). This study revealed through Cox regression analysis that women with stage IV disease and those with ER-/PR-tumor subtype have a higher risk of dying (HR 4.99;] and HR 4.74; [90% CI: 1.88-11.95]), respectively. Conclusions: Our results suggest that the Puerto Rican IBC patient population presents unique characteristics. This is the first research to describe the patient profile and characteristics of women diagnosed with IBC in PR. This research increases awareness about this lethal disease in PR.

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Inflammatory breast cancer (IBC) is an uncommon although highly lethal form of breast cancer. Existing IBC research focuses mainly on United States or European populations, limiting current knowledge of patient profiles in Hispanic populations. Given the unique genetic admixture that exists in PR, we are interested in characterizing IBC within this population to broaden understanding of this disease. We designed a retrospective study which was deemed exempt by the UCC-IRB. A sample of breast cancer patient charts were reviewed at Manatí Medical Center and Pavia Hospital. Of these, 18 eligible subjects with a new primary diagnosis of IBC between 2012-2019 were identified and data was collected from oncologist and pathologist reports. On review, 78% of patients were negative for HER-2/neu receptor overexpression and there was a difference, although not statistically significant (p=0.09) compared to other receptor status. This result differs from other studied populations which place HER-2/neu positivity in the range of 36-60% for IBC. Interestingly, 36.4% expressed the particular signature (ER+, PR+, HER2/neu-) and 36.4% presented as triple negative for tumor markers (ER-, PR-, HER-2/neu-) on pathology review. Our data suggests that within the context of the population studied, IBC is less likely to express HER-2/neu receptor compared to IBC in other populations, and we identified two specific signatures that comprise the majority of the cases studied. To improve patient outcomes for IBC it is critical to have foundational understanding of the disease characteristics and course within a diverse group of patients. This study aims to set such a foundation within the population of PR. With this knowledge, further treatments can be tailored to meet the needs of unique or minority populations such as this one. Citation Format: Zoe C Underill, Mayra Rivera, Michelle M Martinez. Unique hormone receptor signatures of inflammatory breast cancer in a cohort of Puerto Rican women [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B113.