Correlation of tumor size and axillary lymph node involvement with prognosis in patients with T1 breast carcinoma

BACKGROUND. The prognosis of patients with T1 breast carcinoma remains cont roversial. Some studies have shown a low risk of lymph node metastasis and distant failure whereas others have not, possibly due to differences in the definition of tumor size. In this study, the authors assessed the relation between macroscopic tumor size, microscopic invasive tumor size, axillary lymph node involvement, and prognosis in a group of patients with clinicall y lymph node negative disease. METHODS, Between 1968 and 1986, 1865 women with American Joint Committee on Cancer clinical Stage I or II infiltrating carcinoma of the breast were tr eated at the Joint Center for Radiation Therapy with conservative surgery a nd radiation therapy. The study population was limited to 118 patients with clinically negative axillary lymph nodes for whom the macroscopic patholog ic tumor size was identified unambiguously as being less than or equal to 2 .0 cm, who underwent an axillary lymph node dissection with at least 6 lymp h nodes sampled, and for whom the microscopic size of the invasive componen t could be determined. The median follow-up time for surviving patients was 134 months (range, 90-208 months]. No patients with pathologically negativ e axillary lymph nodes received systemic therapy. RESULTS, Macroscopic and microscopic tumor sizes differed by > 5 mm in 17 p atients (14%), by 3-5 mm in 24 patients (20%), and by less than or equal to 2 mm in 77 patients (65%). The macroscopic tumor size was smaller than the microscopic size in 37 patients (31%), larger in 55 patients (47%), and eq ual in 26 patients (22%). Pathologic axillary lymph node involvement was pr esent in 21% of all patients. The risk of lymph node involvement was not si gnificantly different for those patients with tumors less than or equal to 1 cm compared with patients with tumors greater than or equal to 1.1 cm, re gardless of whether tumor size was measured by macroscopic or microscopic e xamination. The 10-year actuarial rate of freedom from distant recurrence ( FFDR) was 91% for lymph node negative patients with macroscopic tumors meas uring less than or equal to 1.0 cm compared with 77% for patients with macr oscopic tumors measuring greater than or equal to 1.1 cm (P = 0.07). When m easured microscopically, the rates were 96% and 72%, respectively (P = 0.00 1). CONCLUSIONS, There often is a discrepancy between microscopic tumor size an d macroscopic tumor size. T1 tumors have a substantial risk of axillary lym ph node metastasis whether measured macroscopically or microscopically. Amo ng those patients with pathologic lymph node negative tumors who are not tr eated with systemic adjuvant therapy, microscopic invasive tumor size is a better predictor of 10-year FFDR than macroscopic tumor size. There is a su bstantial risk of distant failure for patients with tumors whose invasive c omponent microscopically measure greater than or equal to 1.1 cm, whereas t he prognosis for patients with tumors that microscopically measured less th an or equal to 1 cm is excellent. These results suggest that the microscopi c size of the invasive component of breast carcinomas less than or equal to 2.0 cm routinely should be reported. Cancer 1998;83:2502-8, (C) 1998 Ameri can Cancer Society.