Adapted from BMJ 13 September 2025
After having early invasive breast cancer, development of other cancers or a new breast cancer in the other side, over the next twenty years is only 2.1% more than in women who have not had breast cancers.
The risk of contralateral side cancer is comparatively raised in younger women. Radiotherapy tended to increase the risk of contralateral breast cancer and lung cancer. Endocrine therapy tended to increase the rate of uterine cancer but reduced contralateral breast cancers. Chemotherapy increased the rates of leukaemia.
Other cancers that occurred more often in the breast cancer survivors were soft tissue, head and neck, thyroid, oesophagus, kidney, bladder, skin melanoma, haematological, ovarian and stomach cancers. It is thought that part of the adjuvant treatments for breast cancer could contribute to this increased risk.
Researchers looked at the data of 475,000 women who had been diagnosed between 1993 and 2016. After 20 years, 14 out of 100 women will develop some other kind of cancer compared to 12 out of women without the previous breast cancer diagnosis. 6 out of 100 will develop contralateral breast cancer compared to 3 in 100 of the general population.
This study was done because cancer treatments have long been recognised as contributing to the development of second cancers.
Second primary cancer is known to be substantially higher if a woman has a family history of breast cancer or genetic variants such as BRCA1 and BRCA2. Genetic evaluation of each woman who develops breast cancer will hopefully lead to targeted follow up and treatment.
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