Black Women Less Likely to Receive Certain Targeted Therapy Medicines for Metastatic Breast Cancer

If metastatic breast cancer has a PIK3CA mutation, it can be treated with a PI3K inhibitor, a type of targeted therapy medicine. Truqap (chemical name: capivasertib) and Piqray (chemical name: alpelisib) are both PI3K inhibitors.

A study found that Black and white women with metastatic breast cancer had equal rates of PIK3CA mutations, but Black women were less likely to receive a PI3K inhibitor. The results are another example of disparities in breast cancer care.

Researchers have known for some time that Black women, who are less likely than white women to be diagnosed with breast cancer, are nearly 40% more likely to die from the disease. Experts believe that the characteristics of the cancer, including the mutations it has, as well as disparities in treatment, may be to blame for these differences.

For this study, researchers analyzed circulating tumor DNA (ctDNA) results from 1,327 women (including 140 women who were Black and 1,057 who were white) diagnosed with metastatic breast cancer. ctDNA are fragments of the cancer cells’ DNA that enter the bloodstream. A blood test, also called a liquid biopsy, finds ctDNA.

A ctDNA test can show if certain genetic mutations are in the cancer cells, including a PIK3CA mutation.

Overall, 13%-14% of Black and white women had metastatic breast cancer with a PIK3CA mutation. But only about 6% of Black women received Truqap or Piqray, compared to about 29% of white women.

The researchers noted that there could be several reasons for this. Both Truqap and Piqray can cause high blood sugar. In this study, Black women had higher fasting blood sugar levels, so their doctors may have been reluctant to recommend either medicine.

Cost could be another reason. In the United States, Black women are less likely to have health insurance compared to white women, so might have had to pay out-of-pocket for the medicine.

Finally, fewer Black women are in clinical trials than white women. The women in this study were diagnosed between 2015 and 2023. Piqray was approved in 2019 and Truqap was approved in 2023. Before the medicines were approved, the only way a woman could have access to them was through a clinical trial.

The ctDNA results also found other differences that may contribute to the difference in breast cancer outcomes between Black and white women.

Black women had higher rates of mutations in the GATA3 and CCND2 genes than white women. GATA3 mutations are found in about 10% of breast cancers. The cells in breast cancers with a GATA3 mutation look and behave very differently from healthy cells and the cancers tend to be larger in size and higher grade. CCND2 mutations can make cells grow uncontrollably and form tumors.

Currently, there are no treatments that target these two genetic mutations.

Ultimately, Black women survived for shorter periods of time after ctDNA testing than white women.

The researchers concluded that scientists must consider both disparities in care and differences in tumor genetics to tease apart the reasons why Black women’s breast cancer survival rates are so much worse than those of white women.

“Researchers should consider these differences when designing future research and interventions to address the striking and persistent outcomes gap between Black and white patients with metastatic breast cancer,” they wrote.