Colon cancer will claim more than 50,000 American lives this year. Affecting men and women almost equally, 1 in 20 people will be diagnosed at some point in their lives.

Thanks to better screening and ground-breaking new treatments, the death rate from colon cancer has been dropping for more than 20 years. But even the best screening and treatment can’t help those who are unable to afford health care.

The Affordable Care Act was designed to help make sure patients could receive the care they need. But it’s failing many of America’s most vulnerable patients. Congress must step in to make sure the Affordable Care Act lives up to its name and enables people to access the health coverage they need.

When Congress passed health care reform, one key protection for patients was a requirement that insurers cover a minimum set of “essential” benefits. Another protection banned insurers from discriminating based on health status. Despite these protections, many of the insurers offering plans on the new online insurance exchanges are shifting the cost burden of medications to unsuspecting patients in an effort to improve their bottom line.

Put simply, congressional intent is being ignored.

That’s why lawmakers must step in to make sure the ACA lives up to its name by calling for the Department of Health and Human Services to update its essential health benefits rule. Congress must also call on HHS to provide guidance to states that are being asked to assess whether exchange plans are discriminating against certain patients.

As currently structured, all exchange plans are required by law to cover prescription drugs. Each insurer maintains a list of prescription drugs — a formulary — that specifies the drugs it will cover. But most formularies have four or more “tiers” of coverage that place increasing cost-sharing obligations on patients. The surprise comes when you develop a condition whose medications fall into the top tier.

The first tier, usually for the most commonly prescribed medications, might include a modest co-pay of $20. But the highest tier typically involves co-insurance, in which the patient is responsible for a fixed percentage of the cost of a drug, no matter how high. The co-insurance percentage can run to 40 percent or more for drugs that can costs thousands of dollars.

What this means in practice is that patients can get stuck with huge bills. The impact here falls disproportionately on patients with serious medical conditions that require expensive medications such as cancer, multiple sclerosis and HIV/AIDS.

Since a cancer diagnosis can come as a surprise, it’s impossible to plan in advance for the most effective insurance plan. People in that position lose the lottery twice — first with suddenly getting diagnosed with a life-changing condition, then with the bad luck of the financial sacrifice they may have to make to save their lives and get the treatment they need.

Indeed, a recent study by Avalere Health analyzed 123 mid-level exchange plans and found that more than 60 percent place all medication for cancer and other life-threatening conditions on the highest cost-sharing tier.

These formularies seem quite discriminatory, but HHS hasn’t stepped in to crack down on insurers. Congress must call on federal officials to make clear that discriminatory coverage is prohibited.

Such high out-of-pocket drug costs threaten to put medically necessary treatments out of reach for the patients who need them most. Patients are left with little choice but to deplete their savings or retirement funds, declare bankruptcy or skip or refuse treatments.

Researchers at Duke University Medical Center surveyed cancer patients to learn how they coped with these costs. Nearly half described the financial burden as “significant” or “catastrophic.” Forty-six percent had to cut back on basic needs such as groceries. Eighteen percent of patients sold personal possessions or property to help pay for care.

The greater the cost-sharing, the more likely a patient will postpone or forgo medication. According to a study by University of North Carolina researchers, patients with higher co-payments were 70 percent more likely to stop taking their cancer treatment and 42 percent more likely to skip doses.

This is a serious, life-threatening problem. Skipping treatments significantly increases the risk of relapse. Missing even just 15 percent of a prescribed dose can lead to a recurrence of the cancer.

Getting a colon cancer diagnosis is bad enough without adding exorbitant and disproportionate out-of-pocket costs for treatment. If the new health law is to live up to its promise of affordable care, Congress must create a solution and help people get the care they need and deserve.

Jasmine Greenamyer is the chief operating officer of the Colon Cancer Alliance.