ASBS: More Adverse Breast CA Traits in Obese Patients

LAS VEGAS (MedPage Today) -- Obese breast cancer patients tend to have larger, more advanced tumors at diagnosis than normal-weight women, according to a study reported here.

Mean tumor size was about 25% greater in obese women, and significantly more obese than nonobese patients had tumors that had progressed beyond T1. Additionally, obese patients were 25% more likely to have lymph node involvement at diagnosis, researchers told attendees at the Association of Breast Cancer Surgeons meeting.

"Breast cancer screening is highly important in the obese population," Danielle J. Haakinson, MD, of the Mayo Clinic in Phoenix, said at a news conference. "Obese patients are at risk for poor outcomes due to delays in diagnosis, comorbidities, and other factors."

The growing epidemic of obesity in the United States has raised awareness of obesity's association with several types of cancer, including breast cancer. Previous studies have shown that obese breast cancer patients have more adverse characteristics and unfavorable outcomes, including delayed diagnosis, increased rates of lymph node metastasis, increased morbidity from factors such as wound infection and lymphedema, and higher mortality.

Haakinson reported findings from a study to determine more specifically how obese breast cancer patients differ from the general population of breast cancer patients with respect to presentation, tumor characteristics, treatment, and outcome.

Investigators retrospectively reviewed a prospective database of patients treated for invasive breast cancer from 2000 to 2008. They compared obese patients (body mass index ≥30) with nonobese patients. The analysis included comparisons of demographics, cancer characteristics, and treatment, as well as the impact of obesity on survival.

The study included 1,352 patients, 327 (24%) of whom were obese. Obese patients were older; 90% of them were >50 compared with 82% of nonobese patients (P=0.002). Significantly more nonobese patients had palpable lesions (44%) whereas obese patients tended to have lesions that were discovered by imaging (67%, P=0.001). Further exploration of initial presentation showed that obese patients were significantly less likely to have lesions diagnosed by self- or clinical breast exam (28%, 5%) and significantly more likely to have lesions identified on mammography (65%, P=0.007).

Obese patients' tumors had significantly more adverse characteristics compared with nonobese patients:

• Mean tumor size, 2.0 versus 1.6 cm, P<0.001
• T1 disease, 71% versus 79%, P=0.005
• Positive lymph nodes, 31% versus 25%, P=0.026

Nonobese patients were more likely to have multifocal disease (19% versus 14%, P=0.025).

The two groups did not differ significantly with respect to angiolymphatic invasion, tumor grade, tumor type, or markers (triple negative, HER2+, ER+/HER2-).

Significantly more obese patients (P=0.006) had mastectomy (22% versus 16%), and significantly fewer underwent immediate breast reconstruction (9% versus 14%). The two groups were similar with respect to the proportion that received adjuvant chemotherapy, hormonal therapy, and radiation therapy.

Obese patients trended toward worse survival, but the difference from nonobese patients did not reach statistical significance (HR 1.53, 95% CI 0.97-2.53).

"These findings have important clinical implications," Haakinson said. "In our study, obesity was associated with breast cancer that was harder to find on physical examination, larger tumors, higher rates of lymph node metastasis, reduced likelihood of breast reconstruction, and a trend toward higher mortality."

Haakinson had no disclosures.

Primary source: American Society of Breast Surgeons Source reference: Haakinson D et al. "Obese patients present with more advanced cancers: the impact of obesity on breast cancer" ASBS 2010; Abstract.