Definition and Diagnosis of Oligometastatic Bladder Cancer: A Delphi Consensus Study Endorsed by the European Association of Urology, European Society for Radiotherapy and Oncology, and European Society of Medical Oncology Genitourinary Faculty

Background: In contrast to other cancers, the concept of oligometastatic disease (OMD) has not been investigated in bladder cancer (BC). Objective: To develop an acceptable definition, classification, and staging recommendations for oligometastatic BC (OMBC) spanning the issues of patient selection and the roles of systemic therapy and ablative local therapy. Design, setting, and participants: A European consensus group of 29 experts, led by the European Association of Urology (EAU), the European Society for Radiotherapy and Oncology (ESTRO), and the European Society of Medical Oncology (ESMO), and including members from all other relevant European societies, was established. Outcome measurements and statistical analysis: A modified Delphi method was used. A systematic review was used to build consensus questions. Consensus statements were extracted from two consecutive surveys. The statements were formulated during two consensus meetings. Agreement levels were measured to determine if consensus was achieved (≥75% agreement). Results and limitations: The first survey included 14 questions and the second survey had 12. Owing to a considerable lack of evidence, which was the major limitation, definition was limited in the context of de novo OMBC, which was further classified as synchronous OMD, oligorecurrence, and oligoprogression. A maximum of three metastatic sites, all resectable or amenable to stereotactic therapy, was proposed as the definition of OMBC. Pelvic lymph nodes represented the only “organ” not included in the definition of OMBC. For staging, no consensus on the role of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography was reached. A favourable response to systemic treatment was proposed as the criterion for selection of patients for metastasis-directed therapy. Conclusions: A consensus statement on the definition and staging of OMBC has been formulated. This statement will help to standardise inclusion criteria in future trials, potentiate research on aspects of OMBC for which consensus was not achieved, and hopefully will lead to the development of guidelines on optimal management of OMBC. Patient summary: As an intermediate state between localised cancer and disease with extensive metastasis, oligometastatic bladder cancer (OMBC) might benefit from a combination of systemic treatment and local therapy. We report the first consensus statements on OMBC drawn up by an international expert group. These statements can provide a basis for standardisation of future research, which will lead to high-quality evidence in the field.