Sinonasal malignancies make up <5% of all head and neck neoplasms, with an incidence of 0.5–1.0 per 100,000. The outcome of these rare malignancies has been poor, whereas significant progress has been made in the management of other cancers. The objective of the current review was to describe the incidence, causes, presentation, diagnosis, treatment, and recent developments of malignancies of the sinonasal tract. The diagnoses covered in this review included sinonasal undifferentiated carcinoma, sinonasal adenocarcinoma, sinonasal squamous cell carcinoma, and esthesioneuroblastoma, which are exclusive to the sinonasal tract. In addition, the authors covered malignances that are likely to be encountered in the sinonasal tract—primary mucosal melanoma, NUT (nuclear protein of the testis) carcinoma, and extranodal natural killer cell/T‐cell lymphoma. For the purpose of keeping this review as concise and focused as possible, sarcomas and malignancies that can be classified as salivary gland neoplasms were excluded.

Purpose Cyclin‐dependent kinase (CDK) 4/6 inhibitors are integral treatment for advanced hormone receptor positive breast cancer; however, venous thromboembolic events (VTE) occurred in 1%‐5% of clinical trial patients. Thrombosis rates in the real‐world setting remain unclear. We aimed to define the rate of thromboembolic events, risk factors for thrombosis on CDK 4/6 inhibitors and evaluate the Khorana VTE risk score as a predictive tool for VTE in patients on CDK 4/6 therapy. Methods Multicenter retrospective analysis of adult breast cancer patients prescribed palbociclib, ribociclib, or abemaciclib. The primary endpoint was thrombosis during treatment or within 30 days of CDK inhibitor discontinuation. Cox regression was used to model time‐to‐thrombosis, starting from a patient's initiation of CDK 4/6 therapy. The extended Kaplan‐Meier method and Cox modeling were used to assess the effect of time‐varying thrombosis status on overall survival. Results Two hundred and sixty‐six patients were included (89% on palbociclib, 14% on abemaciclib, 7% on ribociclib). Twenty‐nine thrombotic events occurred in 26 (9.8%) women. Of these events, 72% were venous and 34% were arterial. The 1‐year incidence of thrombosis was 10.4% overall, 10.9% on palbociclib, 8.3% on ribociclib, and 4.8% on abemaciclib. Hemoglobin less than 10 g/dL was a statistically significant predictor of thrombosis (HR 3.53, P: .014). Khorana score ranged from 0‐3, with the majority between 0 and 1 and was not predictive of VTE. Thrombosis was associated with reduced overall survival (HR 1.28, P: .128, median 7.3 months) compared to not having a CDK‐associated clot (median 35.7 months). Discussion VTE in our analysis is higher than reported in clinical trials and arterial thrombosis comprised over one‐third of events. The highest incidence was with palbociclib, followed by ribociclib. Khorana score did not predict VTE risk. Larger, real‐world studies are needed. The role for prophylactic anticoagulation is yet to be defined in this patient population.

Angiosarcomas are rare vascular connective tissue tumors originating from the tunica intima, media, or adventitia and may arise in large vessels. Here two cases of primary angiosarcoma of the aorta are described that highlight initial manifestations and unique complications from diffuse arterial tumor emboli, which led to delayed cancer diagnosis. In patients with aortic lesions, imaging characteristics must be thoughtfully reconciled with clinical scenarios, particularly in patients with no additional evidence of atherosclerosis or vasculitis.

e13030 Background: CDKi with endocrine therapy (ET) is approved treatment of metastatic HR+/HER2- breast cancer based on PFS benefit vs ET alone. Outcomes data following CDKi discontinuation (dc) is limited, with trials ongoing in this setting. The reported phenomenon of rapid progression within 4 months of CDKi dc raises concern over CDKi impact on HR+/HER2- MBC biology. This study aims to define outcomes after CDKi dc and identify predictors of progression. Methods: This is a retrospective review of women ≥18 years with HR+/HER2- MBC who received CDKi between 4/1/14 and 12/1/19. Patient and tumor characteristics, pre and post CDKi tx, and reason for CDKi dc were collected. Time to event outcomes from date of CDKi dc (primary = PFS, secondary = Overall Survival, OS) were analyzed with Kaplan Meier estimators and Cox regression. Results: Analysis included 140 patients (median age 65 years), with most MBC (84%) arising from earlier stage disease. 51% of MBCs had visceral disease, and 66% received tx prior to CDKi. The most common CDKi was palbociclib (93%); and most common ET were letrozole (52%) and fulvestrant (40%). Median CDKi tx duration was 9 months (3.5 – 17.4) with 80% dc due to progression. Post CDKi txs included chemotherapy (44%), ET (24%), targeted tx (21%), no further tx (7%) and CDKi tx (4%). Median follow up was 12 months. mPFS post CDKi dc were 6.5 months (95% CI: 5.0 – 7.9) and 11.3 months (95% CI: 4.6 – 23.7) in patients who dc CDKi due to progression or other reasons, respectively (HR 1.77, 95%CI: 1.10-2.85). Among 112 patients who progressed on CDKi, estimated 4-month incidence of post CDKi progression or death was 31% (Table ). mOS post CDKi dc was 15.4 months (95%CI: 13.3-19.0) and mOS post CDKi initiation was 26.5 months (95% CI: 23.3 – 34.3). Visceral disease (HR 1.45, 95%CI: 1.01-2.08) and progression as reason for CDKi dc (HR 1.77, 95%CI: 1.1-2.85) were predictors of PFS (p < 0.05). Receiving fulvestrant with CDKi (HR 1.42, 95%CI: 0.96-1.0), prior chemotherapy in the metastatic setting (HR = 1.39, 95% CI: 0.90 – 2.14), and shorter CDKi duration were associated with non-significant increased risk of PFS. Conclusions: Rapid progression or death at 4 months occurred in 31% of MBCs following CDKi dc due to progression. Ongoing studies to define clinical and molecular characteristics of rapidly progressing tumors are underway to develop targeted tx approaches and improve outcomes.[Table: see text]