Hepatic sinusoidal obstruction syndrome (SOS) is a rare fatal clinical entity seen following hematopoietic stem cell transplant (HSCT). It is more commonly reported to occur following allogeneic HSCT compared to autologous HSCT. Historically, it is known as hepatitis following HSCT. It is thought that endothelial damage to the hepatic venules leading to occlusion of the terminal hepatic venules and hepatic sinusoids is the trigger for the development of SOS. Several risk factors have been associated with this condition. Some of these risk factors are patient related while others are transplant process related. Given the high mortality of this condition, early identification of high-risk patients with severe disease is of utmost importance. The management of SOS varies depending on the severity of the disease. Mild to moderate disease has a good outcome with supportive measures alone, while severe presentation of the disease requires a more aggressive management. Defibrotide is the only Food and Drug Administration-approved therapy and it is reserved for severe cases of SOS. The role of defibrotide as a prophylactic therapy remains under investigation.

e12623 Background: Hematologic markers have been looked at as potential prognostic biomarkers in a variety of cancers. Ni and colleagues (2014) have shown that an elevated pre-treatment lymphocyte-to-monocyte ratio (LMR) was significantly associated with improved disease-free survival (DFS) in patients with locally advanced breast cancer receiving neoadjuvant chemotherapy (NACT). Given the prognostic implications of hematologic inflammatory parameters, we sought to understand if such biomarkers will predict response to neoadjuvant chemotherapy (NACT) in patients with breast cancer. Methods: We conducted a retrospective review of breast cancer patients treated with NACT at our institution (2008-2018). Data on patient characteristics, stage, pathologic characteristics, and blood counts were collected. Blood parameters prior to NACT were used to calculate LMR and neutrophil-to-lymphocyte ratio (NLR). To test the impact of LMR and NLR on pathologic response, a two sample mean test was used first as univariate analysis. Next, logistic regression was employed for multivariate analysis controlling for patient characteristics with interaction of LMR and NLR with ER, PR and HER2 status. Results: A total of 50 patients were included. 38% of patients achieved a pathologic complete response (pCR). The mean LMR was 3.69 (1.4-12.5), and the mean NLR was 2.55 (0.66 – 9.31). On univariate analysis, a high NLR was associated with a higher likelihood of achieving a pCR (OR = 1.64, 95% CI = 1.01-2.63). A high LMR was associated with a higher likelihood of pCR; however, this was not statistically significant (OR = 1.08, 95% CI = 0.78-1.47). On multivariate analysis, patients with HER-2 positive disease with a high LMR had a significantly higher chance of having a pCR (OR = 1.72, 95% CI = 1.06-2.78). Conclusions: Our study showed that NLR was a predictor of pCR in breast cancer patients receiving neoadjuvant chemotherapy. A high NLR was associated with achieving a pCR on univariate analysis. Multivariate analysis suggested that HER-2 positive disease with a high LMR had a significantly higher chance of achieving a pCR. The results of this cohort correlate with previous reports by others showing that pre-NACT LMR and NLR provide prognostic information in patients with breast cancer. Although limited by sample size, this adds to the growing body of literature supporting peripheral blood counts as a biomarker for outcomes in breast cancer.

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