Jayson Tatum scored 32 points to help the Boston Celtics hold off the determined Chicago Bulls on Monday and reach the midway point of their NBA season with the best record in the league.Grant Williams added 20 points, Jaylen Brown scored 19 and Al Horford's eight included a crucial three-pointer with 25.5 seconds remaining in Boston's 107-99 home victory.The Celtics pushed their record to 29-12 after their first 41 games of the 82-game campaign.Meanwhile Denver and Memphis remained neck and neck atop the West, the Nuggets beating the short-handed Los Angeles Lakers 122-109 and the Grizzlies downing the San Antonio Spurs 121-113.Boston, who were stunned by the Oklahoma City Thunder and had to fight to hold off the rebuilding Spurs on their recent road trip, again let a big lead slip but managed to hold on.After Chicago star DeMar DeRozan departed with a thigh injury in the third quarter the Celtics stretched their lead to as many as 16 thanks to a strong offensive showing from Tatum.But the Bulls, with Zach LaVine scoring 15 of his 27 points in the fourth quarter, sliced the deficit to two points in the closing minutes.Horford's three-pointer, off a feed from Tatum, pushed the lead back to five points with 25.5 seconds left and after LaVine missed a three-pointer Tatum threw down a two-handed dunk, drawing a foul and making the free-throw as Boston clinched the win."It's all about trusting your teammates," Tatum said of the pass to Horford as he himself was double-teamed. "Al made a big-time shot."Tatum said that despite Chicago's modest 19-22 record it was a good win."That's a tough team," he said. "Well coached, they play hard, they're long, athletic.