A new study has reported that a high lymph node ratio (number of positive axillary lymph nodes divided by number of examined nodes) increases risk of breast cancer-related death, especially among old women. The study included women aged 50 years and older in the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database who were diagnosed during the period 1988 to 1997 with early stage lymph node positive breast cancer in one breast. The age-lymph node ratio relationship and the effect of age and lymph node ratio on mortality were examined using statistical analysis. Low lymph node ratio was defined as 0.20 or less for purposes of the study, mid-lymph node ratio was defined as 0.21 to 0.65, and high lymph node ratio was set at greater than 0.65.

A positive lymph node ratio-age relationship was found and it rose disproportionately with age: the average lymph node ratio was 0.26 to 0.28 at age 50 to 70 years, but increased to 0.30 at 80 years and 0.40 at 90 years of age. Compared with a 9.8% risk of breast cancer death within five years of diagnosis in women aged 50-59 years with a low lymph node ratio, the risk in women 80 years of age was 12.6% among those with a low lymph node ratio, 18.1% for a mid-lymph node ratio, and 29.8% for a high lymph node ratio. Five-year overall risk of death (including non-breast cancer specific death) increased from 40.8% among women with a low lymph node ratio to 67.4% among those with a high lymph node ratio. The authors conclude that a high lymph node ratio combined with older age was associated with a threefold increased risk of breast cancer death.