Are African-Americans needlessly excluded from taking a new breast cancer therapy?

July 25, 2016–Filipa Lynce, MD, is concerned that her fellow oncologists may not be giving some African American patients with a common type of advanced breast cancer a new drug that can extend survival because of an assumption not yet tested.

Are those with a heritable condition called benign ethnic neutropenia (low white blood count), primarily found in African American women, at a greater risk of infection if they take the drug palbociclib (Ibrance^®)?

The answer is unknown, but Lynce, a Georgetown Lombardi Comprehensive Cancer Center physician researcher, has set out to get some answers.

“Benign ethnic neutropenia”

In the clinical trials testing palbociclib, many women developed a low white cell blood count, though their

rate of infection was very low. As a result, the U.S. Food and Drug Administration established a threshold

white cell blood count as criteria for use of palbocicib, Lynce says.

That threshold forces the elimination of African-American women who have “benign ethnic neutropenia,” or a lower than normal white blood cell count, from receiving the drug.

But studies have suggested that while white blood cell counts are lower in those with ethnic neutropenia, it doesn’t translate into a greater risk of infection.

Investigator-initiated study

“Does that mean that African American patients who could benefit from this drug are pre-empted from trying it?” she says. “Is it safe for them — will they be at a higher risk of infection or not?”

To get those answers, Lynce applied for funds from Pfizer Inc., who developed palbociclib and was awarded a $600,000 grant.

Lynce’s investigator-initiated award was one of five in Pfizer’s first-ever breast cancer research awards, called Advancing Science through Pfizer Investigator Research Exchange (ASPIRE).

Focus on understudied populations

“I think this award shows how committed the company is to look at the safety of their drugs in minorities,” says Lynce, who also is a medical oncologist at MedStar Washington Hospital Center.

“One focus area of my research is to look at the safety and efficacy of medications used to treat breast cancer in populations that have not been included in clinical trials,” she says.

“Minorities in general have been consistently underrepresented in most of the studies, which sometimes can lead to wrong assumptions that conclusions seen in a primarily white population apply to other races and ethnicities,” Lynce explains.

How palbociclib works

Palbociclib slows progression of recurrent ER+ HER2- breast cancer when used with other drugs. In June, researchers presented data showing that combining palbociclib with letrozole extended by 10 months the amount of time the cancer was held in check.

The drug represents a new class of therapy called CDK 4/6 inhibitors that work by stopping the proteins CDK 4 and CDK 6 from signaling. By doing so, palbociclib puts the brakes on cell growth and division in healthy and cancer cells

Broader impact?

Physicians and oncologists know about ethnic neutropenia in African-Americans, but they do not know what it means regarding treatments that may lower white blood cell counts, Lynce says. “That suggests these patients may not be given this new drug as well as other agents.”

The clinical trial studying palbociclib in African Americans will enroll 35 patients, and will soon open at Georgetown Lombardi, MedStar Washington Hospital Center, MedStar Union Memorial Hospital and MedStar Good Samaritan Hospital. Outside of the Washington area, the trial will be open to patients at the University of Alabama at Birmingham Comprehensive Cancer Center, and at the John Theurer Cancer Center at Hackensack University Medical Center in New Jersey.

“Results of this study will give us the information we need about whether African American women receive the same benefit from this medication without increased risk of complications.”

Renee Twombly
GUMC Communications