Objective: To establish a model based on risk factor analysis to guide selective axillary lymph node dissection in patients with T1a and T1b breast cancers.
Design: Retrospective review to determine histopathologic features and patient demographic profiles that may influence the incidence of nodal metastases.
Setting: Primary care and referral centers in Rhode Island and Massachusetts.
Patients: Women with invasive breast cancers with nodal status reported to the statewide tumor registry, the Hospital Association of Rhode Island, and the tumor registry at Baystate Medical Center, Springfield, Mass, between January 1984 and December 1995. There were 12030 patients with breast cancer reported; 2185 (18%) of these had tumors 1 cm or less in diameter.
Main outcome measure: Axillary node metastases.
Results: The nodal status of 377 patients with T1a tumors and 1808 patients with T1b tumors was studied. Seventy-five percent had axillary dissections, and 16% were found to have nodal metastases. Thirty-one percent (29/93) of patients younger than 40 years had positive nodes compared with 15% (241/1546) of older patients (P = .001). The T1a tumors had fewer metastases than the T1b tumors did (11% vs 17%; P = .02). Nuclear grade was available in 49% of cases. Nuclear grades 2 and 3 were associated with nodal involvement twice as often as grade 1 tumors were (P = .002). Patients with no poor prognostic factors had a 7% or less chance of nodal involvement, while patients with all 3 poor prognostic indicators had a 33.5% chance of nodal involvement.
Conclusions: Selective nodal dissection may be possible through risk factor analysis. Prospective registration of complete histopathologic information will allow more comprehensive analysis and may further enhance the selective treatment of patients with minimally invasive breast cancer.