Study: Chemotherapy to Treat Breast Cancer Increases Risk of Lung Cancer


Individuals treated with chemotherapy following a breast cancer diagnosis were more at risk of developing second primary lung cancer.

New findings, published in Epic Research, announced that women diagnosed with breast cancer who received chemotherapy treatment face an increased risk of developing subsequent lung cancer.1

Doctor watching a xray of lung cancer on digital tablet. Radiology concept - Image credit: steph photographies |

Image credit: steph photographies |

In 2022, more than 200,000 new cases were reported in the United States for cases of breast and lung cancer— making them the first and second most common cancers in the country, respectively.2 Additionally, breast cancer is the most diagnosed cancer in women. However, previous studies have found that 10 years after an initial breast cancer diagnoses, about 10% of individuals are diagnosed with a second primary cancer, according to study authors. Although, previous research has not shown the cause to the second primary cancers.1

The study authors noted that in the last decade breast cancer mortality rates have declined, as lung cancer remains the highest cause of cancer deaths, highlighting the need to further research the connection of breast cancer and second primary lung cancer.1,2

The researchers included 2,071,295 women that were between 50 and 84 years old that received a mammogram from 2010 to 2023. However, the study authors noted that women who displayed an evaluated breast cancer risk due to previous breast or lung cancer diagnosis and were screened 3 months prior or started receiving screenings prior to 50 years old were not included in the study.1

In the 5 years following the mammograms screenings, the researchers reported to assess the primary lung cancer in the individuals that received a breast cancer diagnosis. Taking this data, they then compared it with the rate of individuals with lung cancer that were not previously diagnosed with breast cancer.1

The results showed that at 60 months following the mammograms, around 2.0% prevalence of lung cancer after a breast cancer diagnosis was displayed compared to 1.0% without a breast cancer diagnosis. The study authors noted that the risk of lung cancer nearly doubled among individuals with breast cancer.1

However, to identify the cause, the researchers furthered the study by stratifying the individuals with breast cancer based on the treatment they received. The outcomes displayed that at 60 months following the mammogram, nearly 1% were diagnosed with lung cancer after endocrine therapy, almost 3% after radiations, and more than 4% after chemotherapy. The results found that individuals treated with chemotherapy following a breast cancer diagnosis were more at risk of developing second primary lung cancer.1

The study authors noted that more monitoring, like lung cancer screening, could be beneficial in individuals with a history of breast cancer that were treated with chemotherapy.1 Lung cancer screening often aids early detection of lung cancer, which can be cured when found at an early stage. Previous research displayed that lung cancer screening could reduce the risk of dying of lung cancer— emphasizing the researcher’s recommendation for screening following a breast cancer diagnosis.1,3

1. Women with Breast Cancer, Especially Those Who Received Chemotherapy, at Increased Risk for Subsequent Lung Cancer. Epic Research. News release. April 9, 2024. Accessed April 18, 2024.
2. Risk of developing subsequent primary lung cancer after receiving radiation for breast cancer. National Library of Medicine. News release. October 31, 2023. Accessed April 18, 2024.
3. Mayo Clinic. Lung Cancer Screening. February 7, 2024. Accessed April 18, 2024.
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