October 2025
Study finds low risk of second cancer after early invasive breast cancer
Melanie Hinze
Women treated for early invasive breast cancer have a small increased risk of a second primary cancer compared with the general population, according to new research published in the BMJ.
The population-based observational cohort study involved 476,373 women diagnosed with early invasive breast cancer in England from 1993 to 2016 and followed up until October 2021.
In total, 64,747 women developed a second primary cancer. The 20-year absolute risk of developing contralateral breast cancer was about 3% overall, although it was larger for younger women and those with lobular phenotype or higher stage disease at index breast cancer diagnosis.
By 20 years, 13.6% of women had developed a nonbreast cancer – 2.1% more than expected in the general population. In addition, 5.6% had developed a contralateral breast cancer – 3.1% more than expected.
The 20-year absolute excess risk of nonbreast primary cancer was about 2%, with lung and uterine cancer contributing the greatest risk.
About 7% of excess second cancers may have been attributable to adjuvant radiotherapy and systemic therapies, and when categorised according to adjuvant treatment, radiotherapy was associated with increased risk of contralateral breast and lung cancer, endocrine therapy with uterine cancers and chemotherapy with increased acute leukaemia.
Professor Elgene Lim, Laboratory Head and Senior Medical Oncologist and National Breast Cancer Foundation Endowed Chair at the Garvan Institute of Medical Research, Sydney, said, ‘While it is known that patients who survive breast cancer have an increased risk of other new cancers after their first breast cancer diagnosis, the types of cancers and relationship to the treatment they received for their first breast cancer has not been well quantified.’
The most important findings, he said, were that they confirmed there was a risk of new cancers in patients who had survived breast cancer, and a new breast cancer, lung cancer and uterine cancer were the most common types.
Professor Lim emphasised that the additional risk was small, although younger patients and patients with the lobular subtype of breast cancer had the greatest increase in risk.
He said that ongoing breast screening for patients with new breast cancers and vigilance towards other new cancer diagnoses were important for patients who survived breast cancer.