Collecting Long-Term Outcomes in Population-Based Cancer Registry Data: The Case of Breast Cancer Recurrence.

Cancer recurrence is an important long-term outcome of cancer survivors that is often not routinely collected and recorded by population-based registries. In this study, we review population-based studies to determine the current availability, landscape, and infrastructure of long-term outcomes, particularly metastatic recurrence, in women initially diagnosed with nonmetastatic breast cancer (MBC). We reviewed the literature to identify studies that used population-based registry data to examine the distribution of metastatic recurrence in women diagnosed with non-MBC. Data on outcomes and methods of ascertainment were extracted. Registry infrastructure including sources and funding was also reviewed. A total of 23 studies from 11 registries in eight countries spanning Europe, North America, and Oceania were identified and included in the review. Most studies were retrospective in nature and collected recurrence data only for ad hoc studies rather than as part of their routine registration. Definition of recurrence and data sources varied considerably across studies: the cancer-free time interval between the start of follow-up and risk window ranged from the diagnosis of primary tumor (n = 7) to 6 months from diagnosis (n = 1); the start of follow-up differed between initial diagnosis (n = 16) and treatment (n = 7). Cancer surveillance should encompass outcomes among survivors for research and monitoring. Studies are underway, but more are needed. Cancer registries should be supported to routinely collect recurrence data to allow complete evaluation of MBC as an outcome to be conducted and inform health care providers and researchers of the prognosis of both nonmetastatic and metastatic patients with breast cancer.