The association between renal cell carcinoma and multiple myeloma: insights from population‐based data

Study Type – Prevalence (population based cohort) Level of Evidence 3b What’s known on the subject? and What does the study add? Several case‐series have hypothesized a potential association between renal cell carcinoma and multiple myeloma. Nonetheless, this hypothesis has not been systematically explored in a population‐based setting with sufficient sample size to estimate a magnitude of association. Our analyses revealed a bidirectional relation between renal cell carcinoma and multiple myeloma, which typically indicates that common risk factors influence both malignancies. Our findings may be useful for raising awareness among clinicians that a diagnosis of multiple myeloma may be within the spectrum of second malignancies among patients with renal cell carcinoma and that a diagnosis of renal cell carcinoma may be within the spectrum of second malignancies among patients with multiple myeloma. OBJECTIVE • To evaluate the hypothesis of an association between renal cell carcinoma and multiple myeloma. PATIENTS AND METHODS • Data from nine population‐based registries in the Surveillance, Epidemiology and End Results programme were used to evaluate two separate cohorts of patients diagnosed between 1973 and 2006: patients diagnosed with renal cell carcinoma as a primary malignancy ( n = 57 190) and patients diagnosed with multiple myeloma as a primary malignancy ( n = 34 156). • We estimated standardized incidence ratios (SIRs) with corresponding 95% confidence intervals (CIs) by dividing the number of observed cases of multiple myeloma within the renal cell carcinoma cohort and the number of renal cell carcinoma cases within the multiple myeloma cohort by the number of expected cases for each malignancy in the US general population. RESULTS • The renal cell carcinoma cohort yielded 88 multiple myeloma cases during 293 511 person‐years of follow up. Patients with renal cell carcinoma had a higher relative risk of multiple myeloma than the general population (SIR = 1.51, 95% CI 1.21–1.85). • The multiple myeloma cohort yielded 69 renal cell carcinoma cases during 100 804 person‐years of follow up. Patients with multiple myeloma had a higher relative risk of renal cell carcinoma than the general population (SIR = 1.89, 95% CI 1.47–2.40). CONCLUSION • Our analyses revealed a bidirectional association between renal cell carcinoma and multiple myeloma, which typically indicates shared risk factors.