Concordance in survival among first‐degree relatives diagnosed with indolent lymphoid malignancies including chronic lymphocytic leukemia

OBJECTIVES: To investigate concordance in survival time among first‐degree relatives with lymphoid malignancies. METHODS: By linkage of national Swedish registers, we identified 66 430 patients diagnosed with a lymphoid malignancy 1958‐2016 with information on first‐degree relationships and follow‐up until 2017. Among these, we identified pairs of first‐degree relatives with any (N = 3326) or a similar (N = 690) lymphoid malignancy subtype. We defined survival in the first‐degree relative as good, expected, or poor based on tertiles of deviance residuals from a multivariable Cox regression model. Next, we used Cox regression to estimate hazard ratios (HR) of death with 95% confidence intervals (CI) among patients, using the survival of their first‐degree relative as exposure and adjusting for confounders. RESULTS: There was no concordance in survival among first‐degree relatives with any lymphoid malignancy (HR(good) = 1.00 (reference), HR(Expected) = 1.02, 95% CI: 0.89‐1.17, HR(Poor) = 1.12, 95% CI: 0.98‐1.27, P (trend) = .08). Among first‐degree relatives with indolent lymphoma, including chronic lymphocytic leukemia, those with a first‐degree relative to an expected or poor survival had worse outcome compared to those with a first‐degree relative with good survival (HR(Expected) = 1.44, 95% CI: 0.82‐2.53, HR(Poor) = 1.79, 95% CI: 1.07‐3.00, P (trend) = .03). CONCLUSION: Our results support a role of inherited factors in the outcome of indolent lymphoma, including chronic lymphocytic leukemia.