The 5-year survival for breast cancer (BC) is around 93%. Women with BC are living longer and are more likely to develop chronic diseases. Much has been written about the increased risk of developing cardiovascular disease, osteopenia, osteoporosis, bone fractures, hypothyroidism, and secondary malignancies, but there is a lack of information on the temporal pattern of the onset of these and other chronic conditions.

Using data from the Korean National Health Insurance Service—which includes information on all covered inpatient and outpatient visits, procedures, and prescriptions—investigators conducted a retrospective study to evaluate the temporal pattern of the incidence of chronic conditions after developing BC. South Korea has a universal, single-payer national health system.

Women who were aged 20 years or older who had had an incident case of BC between January 1, 2003, and December 31, 2016, were the "BC group." Women who were aged 20 years or older between 2002 and 2016 and who did not have a prior history of cancer served as the "control group." Among those with BC, only those who had received curative treatment were included in the study; a matched sample of controls based on age and region was also identified.

A total of 1,142,643 women underwent baseline health screening and were included in the analysis. Of these women, 1,057,674 did not have a history of BC and 84,969 did have a history of malignancy. The age at baseline in both groups was 46 years. Those who developed BC had 425,132 person-years of follow-up compared with 10,654,144 person-years of follow-up in the control group.

Investigators determined the incidence rate per 100,000 person-years between the BC group and the controls for leukemia, cardiomyopathy, osteoporosis, endometrial cancer, hypothyroidism, pulmonary fibrosis, myeloma, hyperlipidemia, end-stage renal disease (ESRD), type 2 diabetes (T2D), and hypertension (HTN). Adjusted hazard rates revealed a 4.20-fold increase in leukemia, 3.28-fold increase in cardiomyopathy, 3.00-fold increase in osteoporosis, 2.70-fold increase in endometrial cancer, 1.69-fold increase in hypothyroidism, 1.62-fold increase in pulmonary fibrosis, 1.54-fold increase in myeloma, 1.37-fold increase in hyperlipidemia, and a 1.13-fold increase in T2D in those with a history of BC versus those without BC. Only ESRD and HTN were not associated with an increased risk of occurrence between the groups.

For some conditions such as cardiomyopathy, osteoporosis, hypothyroidism, and T2D, risk was highest less than 1 year after diagnosis and decreased when followed 5 or more years after BC diagnosis. Of these conditions, cardiomyopathy, which had the highest hazard ratio, had a 4.30-fold increase less than 1 year from diagnosis, and this decreased to a 2.65-fold at 5 or more years. Between 1 to less than 3 years and 3 to less than 5 years, the highest hazard ratio (HR) was seen for leukemia (HR = 5.15, 95% CI 3.84-6.90 and 5.87, 95% CI 4.27-8.08, respectively). At 5 years or more after diagnosis, the highest HR was for endometrial cancer (HR 3.53, 95% CI 2.76-4.53), and this increased over time starting at 3 years postdiagnosis. Hyperlipidemia, pulmonary fibrosis, and myeloma demonstrated inconsistent patterns of risk over time.

Risk was also increased based on treatment with those receiving chemotherapy, radiation, or hormonal therapy having an increased risk of developing leukemia, cardiomyopathy, osteoporosis, and endometrial cancer. Those who received hormonal therapy were also at increased risk of developing myeloma and ESRD.

This study can serve as a tool to alert pharmacists as to the time course of the occurrence of chronic conditions among BC survivors so that they can take a proactive role in encouraging screening and treatment for these comorbidities.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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