Diet and risk of multiple myeloma: findings from a case-control study.

Multiple myeloma (MM) is one of the most common blood cancers. Despite lengthening survival with modern therapy, it remains largely fatal. Understanding the influence of common modifiable risk factors on MM risk is necessary to inform prevention. We investigated the association between dietary exposures and MM in an Australian population-based case-control study (2010-2016). Incident cases of MM (n 746) were recruited primarily via cancer registries. Controls (n 706) were siblings or spouses of cases. We estimated OR and 95 % CI for associations between MM and dietary exposures, including dietary patterns, fish consumption and a healthy lifestyle index, adjusting for confounders. Higher scores on a modified version of the Alternative Healthy Eating Index-2010 were associated with reduced risk of MM (mAHEI: OR = 0·88, 95 % CI = 0·78, 0·98). There was weaker evidence for reduced risk associated with higher healthful plant-based dietary index score (hPDI: OR = 0·91, 95 % CI = 0·81, 1·02). Increased MM risks were observed with higher scores on empirical dietary indices for inflammatory pattern (OR = 1·20, 95 % CI = 1·07, 1·35), hyperinsulinaemia (OR = 1·15, 95 % CI = 1·02, 1·31) and insulin resistance (OR = 1·21, 95 % CI = 1·08, 1·37). There was no clear evidence of association with MM risk for fish consumption or a healthy lifestyle index. We observed an association between adherence to a healthy diet and lower MM risk. Adherence to dietary patterns with the potential to increase insulin levels, insulin resistance or promote inflammation was associated with increased MM risk. Results of studies assessing dietary intervention for MM prevention could reveal whether dietary modification directly influences MM risk.