* Nike rises after results, outlook
* Biotechs on track for eighth straight advance
* Indexes up: Dow 1.3 pct, S&P 1.1 pct, Nasdaq 1 pct (Updates to early afternoon)
By Caroline Valetkevitch
March 20 (Reuters) - U.S. stocks rose on Friday, putting the S&P 500 on track to snap a three-week streak of losses, following upbeat results from Nike, further gains in biotechs and a pullback in the dollar.
Recent sharp gains in the U.S. dollar had increased worries about the currency's impact on the earnings of U.S. multinationals. S&P 500 earnings projections for the quarter and for 2015 have fallen sharply since Jan. 1.
Among early reporters, Nike jumped 4.8 percent to $103.02 as the biggest boost to the Dow after it posted a quarterly profit that beat market estimates. The world's largest sportswear maker sold more higher margin shoes and apparel, but warned that the stronger dollar would take a toll on its current quarter.
Biotechs were on track for their eighth straight advance, powered by a 7.1 percent climb in Biogen Idec to $464.26.
The company said its experimental drug became the first Alzheimer's treatment to significantly slow cognitive decline and reduce brain plaque in patients with early and mild forms of the disease, according to a small study. The Nasdaq biotech index has gained 7.3 percent since March 10.
The Nasdaq was well above the 5,000 level and about 11 points from its record closing high.
Wall Street's fear gauge, the CBOE Volatility Index, was down 9 percent, and remains below the 13 level. That suggests "the smart money is not really concerned about a downturn right now," said Randy Frederick, managing director of trading and derivatives for Charles Schwab in Austin, Texas.
At 1:38 p.m., the Dow Jones industrial average rose 229.38 points, or 1.28 percent, to 18,188.41, the S&P 500 gained 23.89 points, or 1.14 percent, to 2,113.16 and the Nasdaq Composite added 47.73 points, or 0.96 percent, to 5,040.11.
The S&P 500 is up 2.8 percent for the week and is on track for its first weekly gain in four. The Dow is up 2.3 percent while the Nasdaq is up 3.4 percent for the week.
Largely behind this week's gains was a statement from the Federal Reserve on Wednesday, which signaled a less aggressive approach to raising interest rates than investors had expected.
The market may see heightened volatility heading into the close as a result of quadruple witching - the expiration of stock options, index options, index futures and single-stock futures.
The dollar was off 1.7 percent against a basket of major currencies and was on track for its first weekly decline in five.
Tiffany & Co. shares lost 3.3 percent to $83.50 after the upscale jeweler's quarterly sales fell for the first time in five years and are expected to decline further in the current quarter, hurt by the strong dollar.
Advancing issues outnumbered declining ones on the NYSE by 2,565 to 492, for a 5.21-to-1 ratio; on the Nasdaq, 1,774 issues rose and 946 fell for a 1.88-to-1 ratio favoring advancers.
The benchmark S&P 500 index was posting 75 new 52-week highs and no new lows; the Nasdaq Composite was recording 173 new highs and 21 new lows. (Editing by Bernadette Baum)