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e21567 Background: Merkel Cell Carcinoma (MCC) is a cutaneous malignancy with neuroendocrine differentiation, linked to infection with polyomavirus (MCPyV) in 80% of cases. PD1 inhibitors have recently been approved for this indication with ORR, 33-56%; CR, 11-24%; PFS, about 17 months; OS, about 12 months. Nivolumab was tested in the neoadjuvant setting with similar responses with pathological CR, 47%. Methods: Adjuvant pilot study (NCT03798639) with two immunotherapy regimens administered for one year to patients with completely resected MCC at high risk of recurrence (primary lesion of 2 cm or greater, positive or close margins ( < 2 cm), perineural or lymphovascular invasion, mitotic index ≥ 20 mitotic figures per mm2, lymph node involvement (stage pIIIA or pIIIB) with or without extracapsular extension, or completely resected stage IV disease). Arm 1, nivolumab 480 mg q 4 wks and radiation therapy (RT) 50-60 Gy in 25-30 fractions, per standard of care. Arm 2, nivolumab 240 mg q 2 wks and ipilimumab 1 mg/kg q 6 wks. Primary objective was feasibility and completion of treatment in this population. Safety profile (CTCAE v5.0) and recurrence-free survival (RFS) after 18 months were secondary endpoints. Patients were randomly allocated 1:1. Results: Ten patients were screened from January 2019 until April 2020, when COVID put the study on hold and the sponsor discontinued the free drug supply. Seven were enrolled. Four were allocated to Arm 1 and three to Arm 2. Patient characteristics in Table. All patients have completed treatment and are in follow-up. Arm 1: all four patients completed radiation therapy and immunotherapy with no dose modifications or delays. Arm 2: one patient had nivolumab delayed 2 weeks for cellulitis, and another missed the last four last doses of nivolumab for cholecystitis and pancreatitis requiring surgery, unrelated to the immunotherapy. Adverse events (AE) were as expected. Arm1 caused more grade 2 and 3 AEs then Arm2 (no grade 3). One patient each discontinued treatment, in Arm 1 for progression and Arm 2 for immunotoxicity (temporal arteritis grade 2). One recurrence was observed in Arm 1 and none in Arm 2. Conclusions: The number of patients expected to recur at 1 year is 20%. Our observed data is insufficient to establish efficacy. However with no patient recurring in the ipilimumab arm after 18 months of follow-up and lower observed side effects, we would favor this regimen for the next trial. Clinical trial information: NCT03798639. [Table: see text]

1554 Background: Medically underserved women bear a disproportionate burden of breast cancer (BC) mortality. Early detection is vital for reducing BC deaths. Cancer genetic risk assessment (CGRA) provides an opportunity to identify women at highest risk so that risk-adapted screening can be implemented. The effect of CGRA on mammography adherence among underserved women is unknown. Methods: We conducted a study to test the feasibility of performing cancer genetic risk assessment (CGRA) as part of standard primary healthcare at two Federally Qualified Health Centers in Chicago, IL. Racial/ethnically diverse women age 25-69 without a personal history of BC underwent CGRA at the time of an annual well-visit and received the result from their PCP. Medical record review provided data on mammography adherence. Demographic data and measures of perceived BC risk, BC cultural beliefs, fatalism, and BC worry were collected with an enrollment survey. McNemar’s test compared the rate of adherence to screening mammography before and after implementation of CGRA, defined as completing a screening mammogram within 18 months prior to or following CGRA, resp., among women eligible for screening (age > 40 at study enrollment). Logistic regression models tested for associations between mammography adherence and demographic characteristics/health beliefs. Results: Data was available for 90 participants with increased BC risk (IR) who were eligible for screening and 98 eligible, average risk (AR) participants (in total, 61% black and 37% Latina). Overall, adherence improved from 38% at baseline to 49% following CGRA (p = 0.03). Adherence increased from 35% to 51% among IR participants (p = 0.04), and from 40% to 47% among AR participants (p = 0.39). Data on predictors of adherence will be presented. Conclusions: Implementing CGRA as a standard component of primary healthcare improved adherence to screening mammography among racial/ethnically diverse underserved women. The effect was seen primarily in those with increased risk. This intervention could be used to improve uptake of mammography in the subgroup of underserved women who benefit the most from screening.

e18201 Background: Neutrophil to Lymphocyte Ratio (NLR) is prognostic for cancer patients treated with immune checkpoint inhibitors (ICI). We showed the change in NLR early during treatment to be a stronger, curvilinear predictor, i.e. patients with an intermediate change in NLR performed better than those with large decreases or increases. This led us to re-examine whether NLR is an optimal predictor of overall survival (OS). Methods: A retrospective review of 467 patients with advanced cancer who received ICIs from 2011 to 2017 at the Ohio State University was performed with IRB approval. NLR was collected at the initiation of ICI and on-treatment (median 21, IQR 8 days) and calculated as ratio of absolute neutrophil to lymphocyte counts. Variable selection machine-learning algorithms included fast and frugal decision trees and random forest, performed in R. Results: The machine-learning algorithm fast and frugal decision trees identified the ratio of NLR on treatment to baseline NLR, the NLR on treatment, the change in NLR and the cubic change in NLR to be the most informative predictors of survival at 12 months. A random forest algorithm identified the same four variables as the most important for prediction accuracy. Age, sex and cancer type were the least informative predictors in the model, suggesting the on-treatment NLR variables are of value across wide range of demographics. Conclusions: NLR measured during treatment, and its derivative values of the ratio to baseline, change from baseline, and the cubic change from baseline, hold more predictive value than NLR measured at baseline. Common control variables such as age, and sex showed little effect on the model, suggesting on-treatment NLR is useful across wide demographic space. [Table: see text]

2587Background: Pazopanib is a multi - kinase inhibitor that inhibits angiogenesis. Alisertib is a highly selective inhibitor of mitotic Aurora A Kinase that has been shown to disrupt chromosome se...