Genetic testing could lead to huge scientific breakthroughs in preventing cancer, but it can also be misleading. In Part 1 of a CBS News investigation, we reported about the questionable marketing claims that a blood test can detect cancer before symptoms appear. In Part 2 of the investigation, we look into the booming genetic testing industry that some call the modern-day gold rush.

An average of eight to 10 genetic testing products are being put on the market every day, according to a recent estimate. But in the rush to put tests in physicians' hands, our investigation found profit being placed above scientific proof, reports CBS News correspondent Jim Axelrod.

Last September, a company called Pathway Genomics launched a blood test making game-changing claims.

"CancerIntercept can detect a growing tumor in the body before the patient may notice symptoms. It's like a cancer stethoscope for detecting and monitoring cancer," their marketing video claimed.

We were intrigued. So a few weeks ago CBS News sat down with Pathway CEO Jim Plante to ask him about the evidence.

"Can you tell me about the studies you've done?" Axelrod asked Plante.

"Before we launched the test, we had a clinical study of more than 100," Plante responded.

"Is 100 enough?" Axelrod asked.

"Well, it depends on what you're looking for, right?" Plante said. "You could make an argument that there's never enough data, right? But as you get more information, then you can say more things."

"My question is about the testing. Has your product been clinically validated?" Axelrod said.

"Our test has been validated under the current regulatory requirements," Plante said.

That doesn't mean much since under current FDA regulations, labs that develop tests like these don't have to prove their claims before they go to market.

"It's backwards. It's exactly backwards," said Dr. Stephen Master, director of the Central Laboratory at New York Presbyterian/Weill Cornell Medical College.

"How can a test like that go on the market before it's been validated?" Axelrod asked Master.

"Well the current law allows laboratories a lot of leeway in what they do," Master said. "What seems to have changed though is that there now is a business model that has emerged."

The explosion of unproven lab-developed tests on the market is a big concern for researchers like Dr. Theodora Ross, who runs the cancer genetics program at the University of Texas Southwestern.

"I think that people are not waiting long enough before they send the test out," Ross said.

She agreed the science gets shortchanged in the face of business.

"If the FDA were to come in and say, 'Show me your data,' they couldn't show the data, they should not be testing these patients," Ross said.

"Why not?" Axelrod asked.

"Because it's useless," Ross said.

Of course, most laboratory-developed tests probably are clinically useful, but since companies aren't required to prove it, we just don't know for sure.