Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What's happening: Two days after announcing that it had secured coverage from Aetna for its Medicare Advantage members, and on the heels of positive comments from Wall Street analysts, the colorectal cancer diagnostics company EXACT Sciences Corporation (EXAS -0.46%) soared higher by as much as 10%.

Source: EXACT Sciences Corporation

Why it's happening: Last year, Exact Sciences won FDA approval for its Cologuard diagnostic test, making it the first FDA-approved screening test for colon cancer.

Although it won approval last August, sales were mostly a trickle in the fourth quarter. Exact Sciences reported that its sales totaled just $1.5 million and that expenses tied to launching the test caused it to lose $32.4 million last quarter.

As a result, the company's full year sales were just $1.8 million, and its full year loss was $100 million.

While those results are pretty unspectacular, the company's announcing that it has won coverage across Aetna's 967,000 members for use once every three years could mark an important turning point. It clears the way for the company to enter price negotiations with Aetna and for other insurers to similarly agree to cover the test.

Now what: Since Exact Sciences has been losing a lot of money, investors are embracing this news with open arms. However, it still remains to be seen how many doctors prescribe cologuard and how many patients follow through with taking the at-home test and mailing it to Exact Sciences for evaluation.

Arguably, cologuard addresses an extremely important unmet need for earlier detection of colorectal cancer. According to Exact Sciences, an estimated 23 million Americans over aged 50 years fail to get screened as recommended, and as a result, this cancer is the second deadliest in the United States. The Centers for Disease Control reports that more than 135,000 Americans are diagnosed with the disease every year. Obviously, early detection could prove to be critical to reducing these numbers. However, given the company's cash burn rate, until we begin seeing meaningful sales traction, investors might be best to consider this a highly speculative investment idea.