Breast cancer survivors at greater risk of non-Hodgkin lymphoma

Non-Hodgkin lymphoma (NHL), particularly follicular and mature T/NK-cell lymphomas, is more likely to develop among patients with breast cancer, a recent study has found. Moreover, such risk is greater among those who had been treated with hormone therapy.

Researchers conducted a retrospective cohort analysis of 84,969 women (median age 46 years) who had been diagnosed with breast cancer between 1 January 2002 and 31 December 2016. All participants had received curative treatment. The primary outcome of interest was the development of any type of NHL. A parallel group of 1,057,674 noncancer controls (median age 46 years) was also included.

Over 11,072,988 person-years of follow-up, 1,564 incident cases of NHL were reported. Of these, 105 cases occurred after breast cancer diagnosis (incidence rate, 2,457 per 10,000,000 person-years), while 1,459 cases arose before breast cancer or in noncancer controls (incidence rate, 1,370 per 10,000,000 person-years).

Proportional hazards regression analysis revealed that such incidence rates translated to a significantly elevated risk of NHL associated with breast cancer (hazard ratio [HR], 1.64, 95 percent confidence interval [CI], 1.34–2.00). This effect was driven by the excess risk of follicular lymphoma (HR, 3.56, 95 percent CI, 1.88–6.72), mature T/NK-cell lymphoma (HR, 2.75, 95 percent CI, 1.55–4.90), and anaplastic large cell lymphoma (HR, 7.46, 95 percent CI, 2.70–20.59) associated with breast cancer.

Moreover, NHL risk estimates were much higher in participants <50 years of age (HR, 2.91, 95 percent CI, 2.03–4.16) and in those who had received hormone therapy (HR, 2.68, 95 percent CI, 1.83–3.94). Other treatment modalities had no such impact on NHL risk.