Novel approaches to improve the treatment of rare gynecologic cancers: research opportunities and challenges.

More than 50% of all gynecologic cancers can be classified as rare tumors (defined as an incidence of fewer than six per 100,000). Improved understanding of the molecular pathogenesis of tumors increases the proportion of rare tumors and creates challenges in optimizing the design of clinical trials. Novel trial designs are needed to take forward the development of new treatments in rare tumors. This requires international partnerships, harmonization of treatment, and collaboration to overcome the regulatory barriers to conducting international trials. Although randomized trials can be done in many tumor types, there are some for which conducting even single-arm studies may be challenging. For these tumors, robust collection of data through national and/or international registries could lead through audit to improvements in the treatment of rare tumors.