Aetna shares tumble after slashing outlook

Aetna (AET), whose shares have climbed more than 20 percent over the past month, plunged in after-hours trading after slashing its 2009 operating earnings guidance.

The Hartford-based company expects to earn profit of between $3.55 to $3.70 per share, down from $3.85 to $3.95, Analysts consensus forecasts were for $3.80, according to Thomson Reuters.

"The primary drivers of the revised guidance are: a continuation of higher projected commercial medical costs; and lower projected 2009 Medicare revenue, reflecting an updated view of the risk profile of the Medicare book of business," Aetna said in a statement.