NEW YORK (Reuters Health) May 27 - Very small breast tumors that generate extensive lymph node involvement may be more biologically aggressive than larger tumors with the same degree of lymph node involvement, a study indicates.
"Our study adds to the growing literature that tumor biology may be a more significant predictor of mortality over traditional measures such as tumor size," senior author Dr. Rinaa Punglia, from Dana-Farber Cancer Institute in Boston, told Reuters Health. She said women with very small tumors and significant lymph node involvement "should be treated aggressively."
"Traditionally, larger tumor size and increasing lymph node involvement have been considered independent predictors of increased breast cancer-specific mortality," she and her colleagues noted in their paper.
But they've found that women with very small tumors and at least four positive lymph nodes have a far greater risk of dying of breast cancer than women with larger tumors and at least four positive nodes.
Using the Surveillance, Epidemiology and End Results (SEER) registry, the researchers identified 50,949 women diagnosed between 1990 and 2002 with nonmetastatic T1 and T2 invasive breast cancer and treated with surgery and axillary lymph node dissection.
During a median follow-up period of 99 months, 6,997 (13.7%) died from breast cancer, according to the May 23rd online report in the Journal of Clinical Oncology.
Among women with four or more positive lymph nodes (N2), those with smaller tumors (T1a) had higher breast cancer-specific mortality (hazard ratio, 20.66) than those with larger tumors (T1b), the study team found.
This association of smaller tumor size and higher breast cancer-specific mortality wasn't seen in patients with less extensive nodal involvement.
Estrogen receptor (ER)-negative patients with smaller tumors and extensive nodal involvement (T1aN2+) also had a higher risk of dying from breast cancer (hazard ratio, 24.16) compared to those with ER-negative T1bN2+ disease. This difference wasn't seen in ER-positive patients.
In a commentary, three researchers from Memorial Sloan-Kettering Cancer Center in New York City say this study suggests that "biology trumps anatomy."
Dr. Elizabeth Comen, Dr. Larry Norton, and Dr. Joan Massague write, "Simple anatomic reasoning may not be the most productive way forward in understanding the clinical behavior of cancers and hence prognostication. Elucidating the molecular mechanisms that underlie the biology of individual cancers would seem to be a more useful focus of our attention."
Dr. Punglia and colleagues say their study also supports a growing body of literature showing that African American women have worse breast cancer-specific outcomes, even after adjusting for other known prognostic factors. In the study, African American race was an independent predictor of increased breast cancer-specific mortality (HR, 1.45).
The study also highlights the decrease in breast cancer-specific mortality over time. More recent year of diagnosis was an independent predictor of lower breast cancer-specific death (P < 0.001). The study also supports the "excellent" prognosis for patients with small node-negative disease, with an unadjusted eight-year breast cancer-specific survival of 93.3%.
"Our study adds to the growing literature that tumor biology may be a more significant predictor of mortality over traditional measures such as tumor size," senior author Dr. Rinaa Punglia, from Dana-Farber Cancer Institute in Boston, told Reuters Health. She said women with very small tumors and significant lymph node involvement "should be treated aggressively."
"Traditionally, larger tumor size and increasing lymph node involvement have been considered independent predictors of increased breast cancer-specific mortality," she and her colleagues noted in their paper.
But they've found that women with very small tumors and at least four positive lymph nodes have a far greater risk of dying of breast cancer than women with larger tumors and at least four positive nodes.
Using the Surveillance, Epidemiology and End Results (SEER) registry, the researchers identified 50,949 women diagnosed between 1990 and 2002 with nonmetastatic T1 and T2 invasive breast cancer and treated with surgery and axillary lymph node dissection.
During a median follow-up period of 99 months, 6,997 (13.7%) died from breast cancer, according to the May 23rd online report in the Journal of Clinical Oncology.
Among women with four or more positive lymph nodes (N2), those with smaller tumors (T1a) had higher breast cancer-specific mortality (hazard ratio, 20.66) than those with larger tumors (T1b), the study team found.
This association of smaller tumor size and higher breast cancer-specific mortality wasn't seen in patients with less extensive nodal involvement.
Estrogen receptor (ER)-negative patients with smaller tumors and extensive nodal involvement (T1aN2+) also had a higher risk of dying from breast cancer (hazard ratio, 24.16) compared to those with ER-negative T1bN2+ disease. This difference wasn't seen in ER-positive patients.
In a commentary, three researchers from Memorial Sloan-Kettering Cancer Center in New York City say this study suggests that "biology trumps anatomy."
Dr. Elizabeth Comen, Dr. Larry Norton, and Dr. Joan Massague write, "Simple anatomic reasoning may not be the most productive way forward in understanding the clinical behavior of cancers and hence prognostication. Elucidating the molecular mechanisms that underlie the biology of individual cancers would seem to be a more useful focus of our attention."
Dr. Punglia and colleagues say their study also supports a growing body of literature showing that African American women have worse breast cancer-specific outcomes, even after adjusting for other known prognostic factors. In the study, African American race was an independent predictor of increased breast cancer-specific mortality (HR, 1.45).
The study also highlights the decrease in breast cancer-specific mortality over time. More recent year of diagnosis was an independent predictor of lower breast cancer-specific death (P < 0.001). The study also supports the "excellent" prognosis for patients with small node-negative disease, with an unadjusted eight-year breast cancer-specific survival of 93.3%.
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