Thank you for your comment

Real world data like this is complementary to randomized clinical trials. It's a great starting point to ask relevant questions--are these unusual sites of thromboembolism chance (in this study, cerebral venous thrombosis was only 2 out of 6 events). Rates of VTE with abemaciclib were higher in the randomized phase III trials.

Thanks, [~Albert--Dekker--aldekker@ ] for your insightful comment! Although baseline risk was not explicitly addressed/assessed/documented, the authors did mention the following: "Cerebral venous sinus thrombosis is relatively rare; puerperium, contraception, hyperthyroidism, meningitis, hypercoagulable state,39 meningioma, multiple myeloma, Behcet’s disease, Crohn, ulcerative colitis, and epidural anesthesia are among the known causes, and none were identified in our patients." Is this information useful? Does anybody else recognize limitations in the current study? Please share.

Key Points
• Source: Cancer Management and Research
• Conclusion/Relevance: “In real-world settings, breast cancer patients treated with ribociclib, combined with aromatase inhibitors or fulvestrant, may not be at higher risk for thromboembolic events. However, unusual sites of thrombosis, like CVST [cerebral venous sinus thrombosis], may raise some concerns.”
• In the current study, researchers reviewed the cases of 305 patients with metastatic breast cancer (mBC) treated with ribociclib combined with letrozole or fulvestrant for radiologically confirmed arterial or venous thrombosis. Thromboembolic events (TEE) were deemed ribociclib-related if diagnosed while patients were on the drug, or 4 weeks following the last dose.
• Overall, % of patients had TEE (i.e., 3 pulmonary embolism, 2 CVST, and 1 limb ischemia). All patients were symptomatic. Similar rates of TEE were noted before starting and after ending treatment with ribociclib.
• “Our data, utilizing ribociclib with letrozole or fulvestrant,” wrote the authors, “may not raise significant concerns regarding venous or arterial thrombosis. The few reported TEE are in line with what clinicians usually see in routine daily practice. Additionally, our TEE rates were similar to what patients had encountered prior to, and after stopping CDK4/6 inhibitors. However, the two cases of cerebral venous sinus thrombosis among a total of 6 confirmed cases of TEE, worth emphasis and closer look in future studies. Both patients were on aromatase inhibitors (letrozole), and one of them was also on Gonadotropin Releasing Hormone agonists (GnRHa), too.”
• Limitations of the current study include its retrospective design and lack of randomization which could have excluded some TEE. Furthermore, these findings may not hold with other CDK4/6 inhibitors.

article does not address patients at higher risk at baseline