* Existing home sales hit 9-month low
* Goldman cuts Boeing to sell rating
* Valeant, Salix agree to merger
* Dow down 0.1 pct, S&P down 0.03 pct, Nasdaq up 0.1 pct (Updates to close)
By Caroline Valetkevitch
NEW YORK, Feb 23 (Reuters) - The Nasdaq ended higher on Monday for a ninth straight day following gains in Apple , while the Dow and S&P 500 eased off recent record highs as lower oil prices dragged down energy shares.
Nasdaq's winning run was its longest since September 2010, putting the index closer to its 5,132.52 all-time intraday high, reached in March 2000 just before the dot-com bubble burst. Giving Nasdaq its biggest boost were shares of Apple, which rose 2.7 percent to $133.00, another record close.
Oil prices fell, with WTI crude off 2.7 percent at $49.45 a barrel on oversupply concerns and a stronger dollar, pushing the S&P energy index down 0.4 percent.
The PHLX housing sector index was off 0.5 percent after existing home sales fell to their lowest in nine months in January.
Investors were also reluctant to make big bets before Federal Reserve Chair Janet Yellen's semiannual testimony this week before the Senate Banking Committee, which will be closely watched for any indications on the timing of an interest rate hike.
That is always a potentially big market mover, said Bucky Hellwig, senior vice president at BB&T Wealth Management in Birmingham, Alabama.
"We had some disappointing housing data this morning, and oil prices were lower," which were enough to dampen sentiment, he said.
The Dow Jones industrial average fell 23.6 points, or 0.13 percent, to 18,116.84, the S&P 500 lost 0.64 points, or 0.03 percent, to 2,109.66 and the Nasdaq Composite added 5.01 points, or 0.1 percent, to 4,960.97.
The Dow and S&P 500 eased off record highs from late last week, when a conditional agreement was reached by euro zone finance ministers to extend Greece's bailout.
Insurer stocks gained after the government proposed late Friday to make only a small cut in payments to Medicare plans, a reversal from the much larger cuts in recent years. The announcement was more clearly presented this year than in previous years, analysts said, giving investors more certainty that the worst was behind for this program.
Shares of Humana were up 5.4 percent at $164.52 while UnitedHealth Group Inc gained 3.4 percent to $116.40.
Boeing fell 2.3 percent to $154.74, the biggest drag on the Dow, after Goldman Sachs cut its rating to "sell" from "neutral."
Canada's Valeant Pharmaceuticals International Inc agreed to acquire gastrointestinal drugmaker Salix Pharmaceuticals Ltd in an all-cash deal valued at about $10.1 billion, the companies said on Sunday. U.S. listed shares of Valeant gained 14.7 percent to $198.75 while Salix slipped 1.3 percent to $155.76.
About 5.9 billion shares changed hands on U.S. exchanges, below the 7 billion average for the month to date, according to BATS Global Markets.
NYSE decliners outnumbered advancers 1,539 to 1,506, for a 1.02-to-1 ratio; on the Nasdaq, 1,547 issues fell and 1,182 advanced, a 1.31-to-1 ratio favoring decliners.
The S&P 500 posted 68 new 52-week highs and 1 low; the Nasdaq Composite recorded 117 new highs and 39 lows. (Additional reporting by Caroline Humer in New York; Editing by Bernadette Baum and Nick Zieminski)