Background
The number of breast cancer survivors is increasing, and more women are living with a previous diagnosis of this common cancer (Figure 1). Cancer recurrence is an important long-term outcome that is not often routinely collected or reported by population-based registries. In the case of breast cancer, one of the most important long-term outcomes is metastatic recurrence, which is responsible for the vast majority of breast cancer deaths. This review examines the landscape and (infra)structural needs of population-based studies investigating metastatic recurrence in women diagnosed with breast cancer to inform how this can be achieved in other settings.
Figure 1.
Estimated Number of Prevalent Cases (5-Year) as a Proportion in 2020, Breast, All Ages
Data source: GLOBOCAN 2020. Graph production: IARC (https://gco.iarc.fr/today). World Health Organization. All rights reserved. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the World Health Organization/International Agency for Research on Cancer concerning the legal status of any country, territory, city, or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted and dashed lines on maps represent approximate borderlines for which there may not yet be full agreement.
Methods
We conducted a literature review of studies that used population-based registry data of women who had an initial diagnosis of nonmetastatic breast cancer and had reported outcomes on metastatic recurrence. This review is nested within a systematic review for which the search terms and criteria are described below (Figure 2).
Figure 2.
Search Strategy
DCIS, ductal carcinoma in situ. Four concepts were searched for key words, text, and medical subject headings using PubMed and Web of Science. Articles were screened based on predefined inclusion and exclusion criteria.
Figure 3.
Characteristics and Reported Outcomes of Included Studies
NL, Netherlands; US, United States of America. *Only maximum follow-up provided.
Information on outcomes, methods of ascertainment, and definitions of recurrence were extracted. Registry infrastructure, sources, and funding were also reviewed.
Results
A total of 23 studies from 11 registries in 8 countries spanning Europe, North America, and Oceania were identified. Most studies were retrospective and collected recurrence data for ad-hoc studies rather than routine registry registration.
Definitions of recurrence and data sources varied considerably across studies:
The minimum cancer-free interval between the start of follow-up and risk window ranged from none (n = 4 studies) to 3 months (n = 11) to 120 days (n = 1) to 6 months (n = 1) and was not stated in 6 studies.
The start of follow-up differed between studies from initial diagnosis (n = 16) or treatment date (n = 7).
Conclusions
Including recurrence as an outcome is possible in population cancer surveillance and is key for survivorship research and clinical guidelines. International guidelines to routinely collect recurrence data are needed to allow comparable evaluation of metastatic recurrence to inform health-care providers and researchers of its impact on long-term outcomes of patients with breast cancer.
Footnotes
This content was originally presented as a poster at the North American Association of Central Cancer Registries (NAACCR) 2023 Annual Conference, New Orleans, Louisiana, June 2023.
This work was supported by the Susan G. Komen Foundation (Career Catalyst Grant CCR19608129 to MA and EM).
References
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