This analysis included 444 women with incident lung cancer identified from the Shanghai Women's Health Study. Prediagnosis soyfood intake was assessed at enrollment and reassessed 2 years later. Of the 444 patients with lung cancer, 318 died during follow-up. Initial analyses including all patients showed that higher intake of soyfood was associated with better overall survival after adjusting for demographic and lifestyle characteristics and other nonclinical factors. Larger effect sizes for the association were found after additional adjustment for tumor stage and treatment in analyses including 301 patients with data available on these clinical factors. Compared with the median intake of soyfood, fully adjusted hazard ratios for total mortality associated with the 10th, 30th, 70th, and 90th percentiles of intake were 1.81 (95% CI, 1.26 to 2.59), 1.25 (95% CI, 1.09 to 1.42), 0.88 (95% CI, 0.80 to 0.97), and 0.89 (95% CI, 0.68 to 1.16), respectively. Similar inverse associations were observed for dietary isoflavone intake. In direct contrast to the significant survival advantage among patients with lung cancer who consumed greater amounts of soyfoods, a detrimental impact has been associated with hormone therapy use. Previous research has also shown that post-diagnosis soy intake reduced breast cancer recurrence by 25%. Thus, there is evidence that soy intake improves the prognosis of patients with two types of cancers.
J Clin Oncol 2013;31:1548-53.