Distant Metastasis More Likely in Obese Breast Ca Patients

Major Finding: Women who had a BMI higher than 25 were more likely than normal-weight women to die of breast cancer 10 or more years after diagnosis.

Data Source: Analysis of a registry of nearly 19,000 breast cancer patients.

Disclosures: The investigator received a grant from Novartis Pharmaceuticals, and GlaxoSmithKline sponsored her trip to the meeting. The study was conducted without support from pharmaceutical companies.

SAN ANTONIO — Obese women are substantially more likely than women of normal weight to die of breast cancer, a large Danish registry study concluded.

Researchers from the Danish Breast Cancer Cooperative Group examined extensive health information from nearly 19,000 women with breast cancer, with follow-up data available for up to 30 years post diagnosis.

Breast cancer patients who had body mass indexes greater than 25 kg/m

The disparity showed up early in the course of their disease, Dr. Marianne Ewertz reported at the annual San Antonio Breast Cancer Symposium.

“For distant metastasis, the curves begin to separate after 3 years,” said Dr. Ewertz, professor of oncology at Odense (Denmark) University Hospital.

By 5 years, women who had a BMI of 25-30 had an increased adjusted hazard ratio of developing distant metastasis of 1.42. For those who had a BMI greater than 30, the adjusted hazard ratio of distant metastasis beginning at 5 years was 1.46.

Women with a BMI of 25-30 were 26% more likely and those with a BMI greater than 30 were 38% more likely than normal-weight women to die of their disease 10 or more years after diagnosis, and more likely to die of other causes as well.

Heavier women in the study were older, were more likely to be postmenopausal, had larger tumors, had more positive lymph nodes, and had more tumor invasion into deep fascia than did those with a BMI less than 25. They also had more grade 3 tumors.

However, all of these factors were statistically accounted for in the multivariate analyses of distant metastasis and overall survival.

Poorer outcomes over time may indicate that adjuvant therapy is less effective in obese women than in normal-weight women, Dr. Ewertz suggested.

Inadequate dosing or biologic factors could account for the study's findings, said Dr. Michelle D. Holmes of the Dana-Farber/Harvard Cancer Center in Boston, who was the formal discussant of the presentation.

The impact of lifestyle factors on cancer risk can be “confounding” because they cannot be studied in prospective, randomized trials. Therefore, prospective observational evidence is gathered from huge, well-controlled population databases such as the Danish health registries.

“This is kind of as good as it gets, and it's pretty good,” Dr. Holmes said.

The findings add weight to previous smaller studies, most of which have also found associations between mortality and BMI.

The “vast amount of data” in the Danish registries “allows for a very detailed look at subgroups,” she said.

Dr. Holmes specifically highlighted findings that point to heightened risks of distant metastasis despite equivalent locoregional control, and “a loss of treatment benefit over time in the obese.”

The findings dovetail nicely with recent clinical literature on obese patients with breast cancer that documents profoundly reduced complete responses to neoadjuvant therapy and a two- to four fold-increased likelihood of receiving substandard doses of initial chemotherapy (J. Clin. Oncol. 2008;26:4072-7; J. Clin. Oncol. 2008;26:4060-2).

Social bias, a reluctance on the part of medical oncologists to prescribe full weight-based dosages of medications, and as-yet unidentified biologic differences each may play a role in the poorer outcomes of obese women, Dr. Holmes said.

Major Finding: Women who had a BMI higher than 25 were more likely than normal-weight women to die of breast cancer 10 or more years after diagnosis.

Data Source: Analysis of a registry of nearly 19,000 breast cancer patients.

Disclosures: The investigator received a grant from Novartis Pharmaceuticals, and GlaxoSmithKline sponsored her trip to the meeting. The study was conducted without support from pharmaceutical companies.

SAN ANTONIO — Obese women are substantially more likely than women of normal weight to die of breast cancer, a large Danish registry study concluded.

Researchers from the Danish Breast Cancer Cooperative Group examined extensive health information from nearly 19,000 women with breast cancer, with follow-up data available for up to 30 years post diagnosis.

Breast cancer patients who had body mass indexes greater than 25 kg/m

The disparity showed up early in the course of their disease, Dr. Marianne Ewertz reported at the annual San Antonio Breast Cancer Symposium.

“For distant metastasis, the curves begin to separate after 3 years,” said Dr. Ewertz, professor of oncology at Odense (Denmark) University Hospital.

By 5 years, women who had a BMI of 25-30 had an increased adjusted hazard ratio of developing distant metastasis of 1.42. For those who had a BMI greater than 30, the adjusted hazard ratio of distant metastasis beginning at 5 years was 1.46.

Women with a BMI of 25-30 were 26% more likely and those with a BMI greater than 30 were 38% more likely than normal-weight women to die of their disease 10 or more years after diagnosis, and more likely to die of other causes as well.

Heavier women in the study were older, were more likely to be postmenopausal, had larger tumors, had more positive lymph nodes, and had more tumor invasion into deep fascia than did those with a BMI less than 25. They also had more grade 3 tumors.

However, all of these factors were statistically accounted for in the multivariate analyses of distant metastasis and overall survival.

Poorer outcomes over time may indicate that adjuvant therapy is less effective in obese women than in normal-weight women, Dr. Ewertz suggested.

Inadequate dosing or biologic factors could account for the study's findings, said Dr. Michelle D. Holmes of the Dana-Farber/Harvard Cancer Center in Boston, who was the formal discussant of the presentation.

The impact of lifestyle factors on cancer risk can be “confounding” because they cannot be studied in prospective, randomized trials. Therefore, prospective observational evidence is gathered from huge, well-controlled population databases such as the Danish health registries.

“This is kind of as good as it gets, and it's pretty good,” Dr. Holmes said.

The findings add weight to previous smaller studies, most of which have also found associations between mortality and BMI.

The “vast amount of data” in the Danish registries “allows for a very detailed look at subgroups,” she said.

Dr. Holmes specifically highlighted findings that point to heightened risks of distant metastasis despite equivalent locoregional control, and “a loss of treatment benefit over time in the obese.”

The findings dovetail nicely with recent clinical literature on obese patients with breast cancer that documents profoundly reduced complete responses to neoadjuvant therapy and a two- to four fold-increased likelihood of receiving substandard doses of initial chemotherapy (J. Clin. Oncol. 2008;26:4072-7; J. Clin. Oncol. 2008;26:4060-2).

Social bias, a reluctance on the part of medical oncologists to prescribe full weight-based dosages of medications, and as-yet unidentified biologic differences each may play a role in the poorer outcomes of obese women, Dr. Holmes said.

Major Finding: Women who had a BMI higher than 25 were more likely than normal-weight women to die of breast cancer 10 or more years after diagnosis.

Data Source: Analysis of a registry of nearly 19,000 breast cancer patients.

Disclosures: The investigator received a grant from Novartis Pharmaceuticals, and GlaxoSmithKline sponsored her trip to the meeting. The study was conducted without support from pharmaceutical companies.

SAN ANTONIO — Obese women are substantially more likely than women of normal weight to die of breast cancer, a large Danish registry study concluded.

Researchers from the Danish Breast Cancer Cooperative Group examined extensive health information from nearly 19,000 women with breast cancer, with follow-up data available for up to 30 years post diagnosis.

Breast cancer patients who had body mass indexes greater than 25 kg/m

The disparity showed up early in the course of their disease, Dr. Marianne Ewertz reported at the annual San Antonio Breast Cancer Symposium.

“For distant metastasis, the curves begin to separate after 3 years,” said Dr. Ewertz, professor of oncology at Odense (Denmark) University Hospital.

By 5 years, women who had a BMI of 25-30 had an increased adjusted hazard ratio of developing distant metastasis of 1.42. For those who had a BMI greater than 30, the adjusted hazard ratio of distant metastasis beginning at 5 years was 1.46.

Women with a BMI of 25-30 were 26% more likely and those with a BMI greater than 30 were 38% more likely than normal-weight women to die of their disease 10 or more years after diagnosis, and more likely to die of other causes as well.

Heavier women in the study were older, were more likely to be postmenopausal, had larger tumors, had more positive lymph nodes, and had more tumor invasion into deep fascia than did those with a BMI less than 25. They also had more grade 3 tumors.

However, all of these factors were statistically accounted for in the multivariate analyses of distant metastasis and overall survival.

Poorer outcomes over time may indicate that adjuvant therapy is less effective in obese women than in normal-weight women, Dr. Ewertz suggested.

Inadequate dosing or biologic factors could account for the study's findings, said Dr. Michelle D. Holmes of the Dana-Farber/Harvard Cancer Center in Boston, who was the formal discussant of the presentation.

The impact of lifestyle factors on cancer risk can be “confounding” because they cannot be studied in prospective, randomized trials. Therefore, prospective observational evidence is gathered from huge, well-controlled population databases such as the Danish health registries.

“This is kind of as good as it gets, and it's pretty good,” Dr. Holmes said.

The findings add weight to previous smaller studies, most of which have also found associations between mortality and BMI.

The “vast amount of data” in the Danish registries “allows for a very detailed look at subgroups,” she said.

Dr. Holmes specifically highlighted findings that point to heightened risks of distant metastasis despite equivalent locoregional control, and “a loss of treatment benefit over time in the obese.”

The findings dovetail nicely with recent clinical literature on obese patients with breast cancer that documents profoundly reduced complete responses to neoadjuvant therapy and a two- to four fold-increased likelihood of receiving substandard doses of initial chemotherapy (J. Clin. Oncol. 2008;26:4072-7; J. Clin. Oncol. 2008;26:4060-2).

Social bias, a reluctance on the part of medical oncologists to prescribe full weight-based dosages of medications, and as-yet unidentified biologic differences each may play a role in the poorer outcomes of obese women, Dr. Holmes said.