Jan 28 (Reuters) - Pfizer Inc reported better than expected fourth-quarter results, helped by sales of new treatments for cancer, nerve pain and arthritis, sending shares 3 percent higher in premarket trading. The biggest U.S. drugmaker on Tuesday said it earned $2.57 billion, or 40 cents per share, in the fourth quarter. That compared with $6.32 billion, or 86 cents per share, in the year-earlier quarter, when the company recorded a gain from selling its nutritional products business to Swiss food group Nestle SA. Excluding special items, Pfizer earned 56 cents per share. Analysts, on average, expected 52 cents per share, according to Thomson Reuters I/B/E/S. Global company sales fell 2 percent to $13.56 billion, hurt by competition from cheaper generic forms of its medicines. But it topped Wall Street forecasts of $13.35 billion. Pfizer said it expects full year earnings in 2014, excluding special items, of $2.20 to $2.30 per share. That is roughly in line with Wall Street expectations of $2.28 per share. Company shares traded at $30.55, up from the closing price of $29.66 Monday on the New York Stock Exchange.