Uncovering Professional Attitudes Toward Treatment of Rare Carcinomas of the Breast: An International Practice e-Survey Involving 32 Countries

World Health Organization classification has identified a dozen rare subtypes accounting for less than 10% of all breast cancers (BC), generally not taken into account in treatment guidelines. We evaluated professionals' attitudes toward decision-making regarding rare BC and consensus guidelines needs. In this international e-survey, 236 BC experts from all specialties were contacted through email to fill an online questionnaire about their practices. Eighty-six experts from 32 countries participated (36%); 50% medical oncologists, 21% surgeons, 17% pathologists, and 12% radiation oncologists. General BC care decisions were based on consensus guidelines in 77% of expert, whereas routine individual treatment decisions for BC were made by multi-disciplinary boards in 76%. Only 10% strongly considered rare BC should be treated following existing standard guidelines. Interestingly, 50-80% described individualizing treatment for rare BC according to pathologic subtype. More than 90% of experts would welcome international recommendations for rare BC. This large scale international multi-disciplinary survey revealed overarching concerns centered on several key themes: the lack of resources and data to address these less common BC; the heterogeneous management of rare BC depending on geographical location and specialist training; the demand for international consensus guidelines regarding their diagnosis and treatment.