Stocks advanced on Thursday as optimism about upcoming earnings and investor buying of the quarter's top performers lifted the S&P 500 above a key technical level.

The Dow Jones industrial average <.DJI> added 84.54 points, or 0.70 percent, to end unofficially at 12,170.56. The Standard & Poor's 500 Index <.SPX> gained 12.12 points, or 0.93 percent, to finish unofficially at 1,309.66. The Nasdaq Composite Index <.IXIC> rose 38.12 points, or 1.41 percent, to close unofficially at 2,736.42.

(Reporting by Rodrigo Campos; Editing by Jan Paschal)