What if a company developed cancer-screening tests that examine minute changes in DNA to detect the deadly disease in people who don't have any symptoms? The economic stakes would be huge. And that's why Illumina (ILMN) has attracted high-profile investors including billionaires Bill Gates and Jeff Bezos to help it develop just that kind of technology.

Some cancer specialists, however, are skeptical that it would ever work.

The National Institutes of Health estimates that the cost of treating cancer will reach at least $158 billion by 2020. Billions are already spent on diagnostic testing, a large percentage of which experts say is wasted.

Get Breaking News Delivered to Your Inbox

"If they are able to develop these tests, it could be a tremendous money-maker for them," said Jeffrey Loo, an analyst with S&P Capital IQ who rates Illumina as a "buy." He added that other companies may be attempting to do something similar.

According to San Diego-based Illumina, its test will detect the DNA and RNA called circulating tumor nucleic acids that cancers shed into the blood. Researchers at Illumina and at other laboratories believe that the substance is in the blood of many, perhaps all, people with cancer. The company plans to start a large-scale clinical trial in 2017 and have a test for a single cancer condition by early 2018, with a "pan cancer" test ready by 2019.

Speaking last week at a conference sponsored by JPMorgan (JPM), Illumina CEO Jay Flatley described the task that lies ahead as "both a technically and clinically demanding endeavor," which he said the company can tackle. It plans to spend millions on research that may involve as many as 30,000 people.

"In the earliest stages of the disease, so few molecules from the cancer are present that targeting any small set of mutations for detection fails, simply due to statistical sampling," he said. "The challenge drives the need to look across a very broad set of potential mutations and to sequence at an extraordinary depth."

Illumina has formed a new venture called Grail to develop the screening tests, which has received $100 million in Series A funding, with an additional round of investment expected in six to 12 months.

"We have a tendency to get very excited about the opportunities to find cancers early. That has been the case for decades," said Dr. J. Leonard Lichtenfeld, deputy chief medical officer of the American Cancer Society, in an interview. "We have learned over time that there is a lot more to doing that than meets the eye."

Other companies such as Guardant Health have blood tests that doctors use to develop personalized treatment plans based on a patient's DNA. These people, though, already have cancer. Using this technology for cancer screening in otherwise healthy people has never been tried, according to Dane Leone, an analyst with BTIG.

"The skepticism of the clinical community and even the research community is not surprising," said Leone, who rates Illumina as "neutral," in an interview. "Current technology is not to a point where it detects very, very low levels of this genetic material."

Dr. Maurie Markman, president of Medicine & Science at Cancer Treatment Centers of America, argues that the odds of Grail succeeding aren't good. He wrote in an email that the company's technological prowess in detecting "a particular molecular event in the blood" doesn't tell the whole story about a patient's medical condition.

"Further, there is no data provided that the ability to detect such abnormalities in the blood can be translated into earlier cancer diagnosis or improved survival," he wrote.

Some medical experts are concerned that the Grail test could also lead to false positives.

"With our ability to find cancers earlier in a number of different organ systems, we are finding an increasing number of cancers ... where the person may not benefit from treatment simply because the cancer would have never become evident in their lifetime," Litchenfeld of the American Cancer Society said.

Dr. David Polsky, professor of dermatologic oncology at NYU Langone Medical Center's Laura and Isaac Perlmutter Cancer Center, said the idea of a blood test as a first indication of an internal cancer has great appeal for very aggressive cancers if the test is proven to benefit more people than it may harm.

"Harms are typically due to false positives, which may lead to unnecessary procedures and their associated risks and costs, including patient anxiety," Polsky explained.

He and colleagues published a study this month on a blood test that monitors blood levels of DNA fragments from dead melanoma cancer cells. The study showed that the test does a better job than the current standard -- which measures blood levels of an enzyme -- at tracking the severity and potential spread of metastatic melanoma in patients already diagnosed with the disease.

Polsky said he's not familiar with the details of Illumina's study plans, but he noted that any test would need publication in a top peer-reviewed medical journal for it to be broadly accepted.

He also mentioned Food and Drug Administration hurdles. "The FDA has become very interested in regulating these types of tests, so in addition to a successful study being published, the FDA may require that such tests also meet their standards."

For now, though, the optimists are ruling the day with Grail. According to S&P Capital IQ's Loo, Grail will benefit from its access to capital and its relationship with Illumina.

"A lot of companies try to be innovative," he said. "A lot of them fail, but some are successful."