Adjuvant chemotherapy with and without tamoxifen in the treatment of primary breast cancer: 5-year results from the National Surgical Adjuvant Breast and Bowel Project Trial.

In this National Surgical Adjuvant Breast and Bowel Project (NSABP) clinical trial, 1,891 women with primary operable breast cancer and positive axillary nodes were randomized between Jan, 1977 and May 1980 to receive L-phenylalanine mustard (L-PAM) and 5-fluorouracil (5-FU) either with or without tamoxifen (TAM)-PFT. This report presents life table probabilities, cumulative odds ratios, and P values for disease-free survival (DFS) and survival at yearly intervals through 5 years of observation (mean time on study, 72 months). When patients were examined overall without regard for any discriminant associated with outcome, ie, age, number of positive nodes, or tumor receptor status, there was a significant prolongation of DFS (P = .002), but not survival through the fifth postoperative year. The benefit was almost entirely restricted to those greater than or equal to 50 years with greater than or equal to 4 positive nodes. In that group there was a 66% greater chance of remaining disease free if PFT was received (P less than .001), and there was also a significant survival benefit (P = .02). The advantage from PFT was found to be associated with tumor estrogen receptor (ER) and progesterone receptor (PR) as well as patient age and nodal status. Overall there was a significant improvement in DFS from PFT in those having tumors with an ER or PR level greater than or equal to 10 femtomole (fmol) (P = .01 and .009, respectively). No significant benefit in DFS or survival has been observed in patients less than or equal to 49 years old related either to nodes or tumor receptor status. Survival continues to be adversely affected by TAM in those patients (less than or equal to 49 years old), particularly when their tumors have a PR of 0 to 9 fmol (P = .007). In patients greater than or equal to 50 years old with four or more positive nodes, a significant DFS benefit persisted through the fifth year of observation in those having tumor ER or PR levels greater than 10 fmol (P less than .001 and .002). The advantage was observed in patients 50 to 59 years old as well as those 60 to 70. Women in the older decade demonstrated some advantage from PFT when their tumor ER or PR was 0 to 9 fmol. The most likely explanation for this finding is analytical error in receptor analyses.(ABSTRACT TRUNCATED AT 400 WORDS)