axillary nodal examination in breast cancer: how much is enough? evidence for a new minimum

background: axillary nodal spread is an established prognostic factor in breast cancer. axillary nodal dissection and subsequent pathological examination is considered the gold standard technique of assessing the axilla for metastatic disease. a minimum of ten level i axillary nodes are required to be examined before an axillary specimen can be reliably labeled as disease free. this recommendation is based on a mathematical prediction model and such methodology has certain inherent limitations. in this study, we sought to revisit this concept of minimum nodes required to deem an axilla as true negative by using a linear correlation model. methods: medical records of 165 consecutive breast cancer patients attending a medical oncology department for adjuvant therapy were assessed for inclusion. one hundred and forty-five breast cancer patients in clinical stages i-iii met the inclusion criteria. patients referred after neoadjuvant chemotherapy, breast conservation surgery, palliative mastectomy, and mastectomy for metastatic disease were excluded from the study. the study samples were segregated into groups of 1-5, 6-10, 11-15, 16-20, 21-25, and more than 25 nodes. a linear regression model was used to assess the association between the nodal positivity and nodal groups. the spearman rho with p value was calculated for the model. factors influencing the nodal yield of an axillary specimen were selected from the published literature and the same variables were evaluated in the study cohort. results: a total of 1882 nodes were harvested from 145 axillary specimens and 320 nodes were positive for metastatic disease. the mean nodal harvest per axillary specimen was 11 nodes. the linear correlation model evaluating the association between nodal positivity and total nodal yield showed a spearman correlation coefficient of rho = - 0.82 with p=0.04. to avoid bias due to the uneven sample size, the nodal ratio was calculated for each group and the linear association model reapplied to test the association with the total nodal harvest. a spearman rho of r = -0.94 with p=0.004 was obtained. the nodal groups tested for significance showed p= 0.0001 for the group 1-15 nodes. evaluation of the factors likely to influence nodal yield showed that age (p=0.15) and obesity (p=0.67) had no effect on the nodal harvest. tumor stage (p<0.001) and operating surgeon (p=0.0001) had a significant effect on the total nodal harvest. conclusions: the recommendation of a minimum of ten axillary nodes to be examined to determine true negativity of an axillary specimen needs reassessment. a new minimum of fifteen nodes is suggested before an axillary specimen is reliably deemed free of metastatic disease.