A possible effect of iron levels on risk of cancer as well as vascular disease was recognized at trial inception. Participants with visceral malignancy within the preceding five years were excluded from this study. However, information was collected prospectively on the occurrence of new visceral malignancy and cause-specific mortality including death due to cancer. As reported in the Journal of the National Cancer Institute, a new visceral malignancy was diagnosed during follow-up in 60 control and 38 iron reduction participants, a 37% (HR 0.63; 95% CI = 0.42 - 0.95, p = 0.026) decrease in risk with iron reduction. Reduced cancer risk with iron reduction was confirmed on time-to-event analysis (HR = 0.65; 95% CI = 0.43 - 0.97, p = 0.036). Reduced risk was observed for several common tumor types. Iron reduction participants had lower cancer - specific mortality and lower all-cause mortality in participants diagnosed with cancer (HR = 0.39; 95% CI = 0.21 - 0.72, p = 0.003 and HR = 0.49; 95% CI = 0.29 - 0.83, p = 0.009 respectively), compared to control participants. MFFL during follow-up in those participants randomized to iron reduction who developed cancer were comparable to levels in control participants (t93 = 0.8, p = 0.428). The MFFL in participants randomized to iron reduction developing cancer was 127 ng/mL, 95% CI = 71.2 - 183.0. The MFFL was significantly lower in participants not developing cancer, 76.4 ng/mL, 95% CI = 71.4 - 81.4, p = 0.017). Participants randomized to iron reduction developing cancer appeared to be relatively non-compliant with intervention.