In a letter dated April 22 to Angela Braly, WellPoint's chief executive, Sebelius said she was surprised and disappointed to learn from a Reuters report that the company has specifically targeted women with breast cancer for aggressive investigation with intent to cancel their policies.

As you know, the practice described in this article will soon be illegal, Sebelius wrote. The Affordable Care Act specifically prohibits insurance companies from rescinding policies, except in cases of fraud or intentional misrepresentation of material fact.

Reuters reported on Thursday that WellPoint was using a computer algorithm that automatically targeted patients recently diagnosed with breast cancer. The software triggered an immediate fraud investigation by the company as it searched for excuses to drop coverage, according to government regulators and investigators.

WellPoint should not wait to end the unconscionable practice of deliberately working to deny health insurance coverage to women diagnosed with breast cancer, Sebelius wrote in her letter. I urge you to immediately cease these practices and abandon your efforts to rescind health insurance coverage from patients who need it most.

Breast cancer is the second-leading type of cancer among women, has touched millions of families, and will affect one in eight American women during their lifetime, Sebelius wrote.

I hope you will consider these women and their families as you work to end this harmful practice, she wrote.

In a statement responding to the Reuters story, Wellpoint said it uses software to look at a series of diagnostic codes covering conditions that patients would likely have known about when they applied for insurance coverage, but maintained it does not single out breast cancer.

The company said it changed its rescission practices to ensure they are handled appropriately after a 2006 review of its policies prompted by public concern.