Dear Editor,

It is generally accepted that women with breast cancer (BC) have an increased risk of venous thromboembolism (VTE) compared with age-matched women without cancer. Metastatic disease, chemotherapy (Chavez-MacGregor et al. 2011) and tamoxifen treatment (Pritchard et al. 1996) are all risk factors for increased VTE risk. Particularly, a 6% annual VTE incidence while undergoing chemotherapy, and up to 1 month after, has been recently reported in a cohort study, showing that VTE risk was markedly higher in the 3 months after initiation of tamoxifen, but not aromatase inhibitors (Walker et al. 2016).

As BC is the most common female cancer, treatment-related VTE poses serious concerns in terms of both patient care and health costs, while thromboprophylaxis could provide an opportunity to substantially improve BC management. Nonetheless, consensus guidelines do not recommend routine prophylaxis for the primary prevention of VTE in cancer outpatients receiving chemotherapy, except for selected high-risk patients (Khorana et al. 2014). To guide the oncologist community in VTE risk assessment, the International Society for Thrombosis and Haemostasis has recently proposed the adoption of the Khorana score (Khorana et al. 2014).

In this context, the PTV Bio.Ca.Re. (Policlinico Tor Vergata Biospecimen Cancer Repository) and the Interinstitutional Multidisciplinary Biobank of the IRCCS San Raffaele Pisana (SR-BioBIM) are actively involved in the recruitment of BC outpatients undergoing chemotherapy, who are prospectively followed under appropriate Institutional ethics approvals, as part of a clinical database and biobanking project. Among them, 390 patients with primary (84%) or relapsing (16%) BC completed the clinical assessment for VTE. As expected, VTE incidence was lower in BC compared with other cancer types, with only 9 (2.3%) events recorded during treatment, mostly in advanced/metastatic stages. Nonetheless, since BC is considered a low-risk tumour in the Khorana score (Khorana et al. …