Centene's ( CNC) shares were plummeting Tuesday after the company dramatically lowered its profit forecast for this year, citing detrimental medical-cost trends. For 2006, Centene is now expecting to earn 95 cents to $1.04 a share, down from its previous guidance of $1.53 to $1.70. That sent the stock reeling, and it was lately down $7.36, or 35%, to $13.68, making it the biggest percentage loser on the New York Stock Exchange. Volume was extremely heavy. The operator of health plans estimated that it will earn 10 cents to 12 cents a share in the second quarter, including an adjustment of roughly $9.7 million, or 14 cents a share, for additional medical costs, primarily in Indiana and Texas. Analysts surveyed by Thomson Financial were forecasting earnings of 28 cents for the second quarter and $1.62 for the year. "We are truly disappointed and are working to resolve the factors which impacted our second-quarter results, and will provide additional details on our conference call next week," said Michael F. Neidorff, Centene's chairman and CEO. "We are in the process of finalizing an in-depth analysis to determine the root cause of these issues." Centene said it's in the process of completing its financial results for the second quarter. The company plans to report its earnings July 25.