Colorectal cancer kills more Americans than all other forms of cancer but one. More than 140,000 people were diagnosed with the disease last year.

Fortunately, help appears to be on the way. Zaltrap, a drug recently approved by federal regulators, produces a "statistically significant improvement in overall survival," according to a new study published in the Journal of Clinical Oncology.

Some of the nation's top doctors are unmoved. The renowned Memorial Sloan-Kettering Cancer Center in New York has announced that it will not give Zaltrap to patients. Doctors there say that the drug is too expensive.

Such a narrow-minded focus on cost not only harms patients but also impedes the development of the next generation of life-saving medicines.

Sloan-Kettering says that a similar cancer drug, Avastin, is more cost-effective than Zaltrap. The former costs some $5,000, and the latter, $11,000.

But their price tags should be immaterial. The true value of each treatment depends on how an individual patient responds to it.

Such rationing as this could become common under Obamacare. The law creates a "Patient-Centered Outcomes Research Institute," which is charged with determining the relative effectiveness of various treatments. The institute is ostensibly prohibited from considering cost. But with the government footing the bill -- and crumbling under the weight of health costs -- researchers could feel pressure to find that expensive medicines aren't worth the money.

Avastin and Zaltrap both cut off blood flow to tumors, but by different means. Avastin latches onto and disables something receptors that help tumors grow blood cells. Zaltrap, on the other hand, "traps" the proteins that start blood cell growth. Both drugs can thus keep tumors from growing. Neither is a cure -- but each can enhance other cancer treatments, like chemotherapy.

But treatments cannot be administered on a one-size-fits-all basis. One patient may live longer than the averages would predict thanks to Zaltrap, while another may react unfavorably to its side effects and thus be a better candidate for Avastin. As with most treatment regimens, individual patients respond differently to different drugs.

In the end, shouldn't patients and their doctors decide collaboratively whether the extra life that a drug can offer is worth the price tag?

For one thing, there is a real dearth of treatments available for late-stage colorectal cancer, so Zaltrap is helping fill a vacuum. For another, drug development is an incremental process. Scientists don't simply cure cancer in one fell swoop -- each new treatment improves on a previous one. Zaltrap may be the next step toward an actual cure.

Life expectancy for cancer patients has increased about 3 years since 1980, and 83 percent of those gains are attributable to new treatments, according to the Journal of Clinical Oncology. A study published by the National Bureau of Economic Research found that medicines alone account for between 50 and 60 percent of the increase in survival rates since 1975.

Pharmaceutical companies cannot turn out innovative treatments unless they have profits from the sale of their current products to invest in research and development. Last year, the industry spent $49.5 billion on research and development. Yet, the Food and Drug Administration approved just 35 new drugs. That comes to $1.4 billion for every new drug that reached the market.

New cancer drugs are expensive because they cost a fortune to develop and get through the FDA's approval process and on to patients.

As health costs rise, officials may be tempted to hold down the price of expensive drugs by fiat. But as Marijn Dekkers, the chief executive of Bayer AG, recently warned, "The danger of pushing the prices of prescription drugs down, down, down is that at some point the business model of developing these drugs will lose its attractiveness."

Taking promising treatments off the table because they are expensive will only hurt patients and deprive drug researchers of the resources they need to create newer, better, and more cost-effective treatments.

Sally C. Pipes is president, CEO and Taube fellow in Health Care Studies at the Pacific Research Institute. Her latest book is "The Pipes Plan: The Top Ten Ways to Dismantle and Replace Obamacare" (Regnery 2012).