We measured OPN in plasma by ELISA , and in tumors by immunohistochemistry , in 624 ( 94 % ) and 462 ( 69 % ) , respectively , of 667 postmenopausal women with hormone responsive early breast cancer treated by surgery followed by adjuvant treatment with tamoxifen + / - octreotide in a randomized trial ( NCIC CTG MA .14 ; National Cancer Institute of Canada Clinical Trials Group Mammary .14 ) .