Optimal indications of endocrine therapy alone as adjuvant systemic treatment of breast cancer

We examined the validity of the St Gallen algorithm for Japanese breast cancer patients and sought the optimal indications of endocrine monotherapy as adjuvant systemic treatment. According to the 2005 St Gallen algorithm, endocrine responsiveness (responsive, uncertain, or non-responsive) and recurrence risk (low, intermediate, or high) were assessed in 436 invasive breast cancer patients, who underwent surgery and adjuvant therapy of tamoxifen alone in 1982–1993. Furthermore, intermediate-risk patients were divided into three groups based on lymph node metastasis and number of risk factors as follows: Group A, negative lymph node metastasis and one risk factor; Group B, negative lymph node metastasis and two to five risk factors; and Group C, positive lymph node metastasis. Cumulative 10-year recurrence-free survival (RFS) rates of each type were calculated. Recurrence-free survival was as follows: endocrine responsiveness; responsive: 86.0%, uncertain: 79.5%, non-responsive: 72.4%, risk category; low: 93.3%, intermediate: 84.0%, high: 59.6%, intermediate-risk patients; Group A: 93.5%, Group B: 88.2%, and Group C: 75.0%. In conclusion, patient classification based on St Gallen algorithm appears valid in Japanese breast cancer patients. Endocrine monotherapy may be sufficient as adjuvant treatment in the intermediate-risk patients, in which only one risk factor was present without any metastatic involvement in lymph node.