Previous research on screening for breast cancer has shown that screening reduces risk of death from breast cancer in women as it finds cancer early. However, overdiagnosis can also be harmful. Overdiagnosis is defined as pre-cancerous and early-stage cancers being found through screening that would never become known or cause problems if screening did not happen. There is no agreement on the amount of overdiagnosis occurring.
This research used data on cancers diagnosed in 2018 from the BreastSurgANZ Quality Audit. Cases were split into two groups: possibly over-diagnosed and not over-diagnosed. The study found:
- A large number of higher risk cancers were found through a screening program.
- Women with cancer not found through screening were twice as likely to have more extensive surgery such as mastectomy or axillary lymph node dissection and were more likely to have chemotherapy, immunotherapy or a combination of chemotherapy and radiotherapy recommended.
- Although 16% of breast cancers found through screening were in the possibly over-diagnosed group, this group was not overtreated. There were fewer intense treatments, with less than 1% having chemotherapy recommended, less than 10% radiotherapy, 6% endocrine therapy and no women in this group having combination chemotherapy and radiotherapy recommended. Also, only 2% had mastectomy and less than 1% axillary lymph node dissection.
The authors of the research argue that reducing deaths is not the only important outcome of screening programs and that reducing treatment intensity is also important as it affects the quality of life for the patient in the long-term. They recommend that when deciding whether to screen or not, women are given full information on the risks, such as overdiagnosis, and benefits, including less harmful treatments.
Reference:
Kathy Dempsey, Daniel SJ Costa, Meagan E Brennan, G Bruce Mann, Kylie L Snook, Andrew J Spillane - Benefits and harms of breast cancer screening revisited: a large, retrospective cross-sectional study quantifying treatment intensity in women with screen-detected versus non-screen-detected cancer in Australia and New Zealand: BMJ Oncology 2023;2:e000100. Paper: https://doi.org/10.1136/bmjonc-2023-000100