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Trastuzumab underutilized among older, black women with HER-2–positive breast cancer
Approximately half of women aged 65 years or older with early-stage, HER-2–positive breast cancer did not receive targeted therapy with trastuzumab, according to the results of a national cohort study.
Older back women appeared especially unlikely to receive trastuzumab (Herceptin, Genentech/Roche).
“This is significant because we know that there is a large number of women here who are not receiving a therapy that we know would give them a better chance for survival,” Katherine Reeder-Hayes, MD, clinical assistant professor at University of North Carolina School of Medicine and researcher at UNC Lineberger Comprehensive Cancer Center, said in a press release. “In many ways, this is not surprising, because we know that across many types of breast cancer therapy, black women are less likely to receive treatment for a clinically similar disease.”
Lisa A. Carey
Stacie B. Dusetzina
Trastuzumab is frequently used in the adjuvant setting for stage I to stage III HER-2–positive breast cancer; however, the rates and patterns of its use had not been studied at a population level.
The addition of HER-2 information to the SEER–Medicare database in 2010 allowed Reeder-Hayes and colleagues to analyze patterns of trastuzumab use among older women with breast cancer and to evaluate possible disparities associated with receipt.
The researchers examined data from 1,362 women with Medicare diagnosed with incident stage I to stage III HER-2–positive breast cancer in 2010 and 2011.
More than 50% of patients in the cohort were diagnosed at an age younger than 75 years (65-69 years, n = 354; 70-74 years, n = 362).
Eighty-five percent of the cohort was non-Hispanic white, 7.6% were black and 7% were another race.
Reeder-Hayes and colleagues used insurance claims data to determine trastuzumab receipt in the 12 months following diagnosis, as well as chemotherapy drugs used in concert with trastuzumab.
Fifty percent (n = 1,162) of non-Hispanic white women and 40% (n = 104) of black women used trastuzumab within 1 year of diagnosis.
A smaller proportion of black women used trastuzumab than white women at every disease stage (stage I, 24.4% vs. 37.5%; stage II, 48.9% vs. 57.2%; stage III, 56.3% vs. 73.9%).
After adjusting for age, comorbidity, disease characteristics, type of locoregional therapy and neighborhood-level poverty, black women had a 25% lower likelihood of receiving trastuzumab within 1 year of diagnosis than white women (RR = 0.75; 95% CI, 0.6-0.93).
Disease characteristics associated with an increased likelihood of receiving trastuzumab included large tumor size (all sizes greater than T1a), node-positive disease, and moderately or poorly differentiated tumors.
Older age ( 75 years) and a Charlson comorbidity index score greater than 1 were associated with decreased likelihood of trastuzumab receipt. Hormone receptor-positive status alone did not serve as an independent prognostic factor.
Treatment platform appeared somewhat associated with trastuzumab receipt. The 397 women who underwent breast-conserving surgery and radiation were slightly less likely to receive trastuzumab than the 574 women who underwent mastectomy (RR = 0.73; 95% CI, 0.63-0.86).
The researchers could not analyze racial disparities based on chemotherapy receipt due to the small sample size of minority women for most regimens.
Study limitations included the exclusion of 391 women with the HER-2 borderline phenotype and the potential underrepresentation of comorbidities, such as cardiac risk factors, that may vary by race and influence chemotherapy receipt.
The researchers also could not definitively determine whether or not HER-2–directed therapies were offered to all patients.
“Fifty percent of white women and 60% of black women didn’t get a drug that improves survival by nearly 40% — if confirmed, these are terrible numbers,” Lisa A. Carey, MD, Richardson and Marilyn Jacobs Preyer distinguished professor in breast cancer research at UNC School of Medicine, said in a press release. “There was underutilization broadly of what is a very effective therapy — we must find out why.”
Low trastuzumab receipt may be due to cost and insurance status, Stacie B. Dusetzina, PhD, assistant professor of pharmaceutical outcomes and policy at UNC Eshelman School of Pharmacy, said in a press release.
“Herceptin costs about $5,000 per infusion, so women without supplemental Medicare insurance would have to pay about 20% of that amount out of pocket,” Dusetzina said. “However, we’re not sure the cost sufficiently explains the shocking underuse of what is a highly effective treatment for this type of cancer.” – by Cameron Kelsall
Disclosure: Carey reports research funding from Genentech and GlaxoSmithKline. The other researchers report no relevant financial disclosures.