BOSTON — With another Game 7 victory at stake, LeBron James would not sit out.

And he would not be denied an eighth straight trip to the NBA Finals.

The four-time league MVP scored 35 points with 15 rebounds and nine assists Sunday night, leading the Cleveland Cavaliers to an 87-79 win over the Celtics and eliminating Boston from the Eastern Conference finals in the decisive seventh game.

“He’s had a lot of gaudy games,” Cavaliers coach Tyronn Lue said. “But I just think Game 7, in Boston, all the circumstances that surround Boston, the history ... to come here in a hostile environment: (it’s) right there.”

In the first close game, the lowest-scoring and the first victory for a road team in the series, James played all 48 minutes, scoring 12 of his points in the fourth quarter for his sixth straight Game 7 win. Lue used his timeouts to get his star an extra few minutes of rest when he could, and James didn’t warm up at halftime to conserve his energy.

“It was asked of me tonight to play the whole game,” he said. “And I just tried to figure out how I can get through it.”

James played all 82 regular-season games for the first time in his career and is already at 100 for the year with at least four more to come. He tired late in Game 5, when the Celtics won their 10th straight at home this postseason.

Celtics coach Brad Stevens said the plan was to wear James out.

Nice try.

“Our goal going into the series was to make him exert as much energy as humanly possible and try to be as good as we can on everybody else,” Stevens said. “For the most part, I thought we were pretty good at that ... but he still scored 35. It’s a joke.”

Now, the only question is who the Cavaliers will play for a chance at their second title in three years: The Rockets host Game 7 of the Western Conference finals against Golden State tonight, and the winner will host the opener of the NBA Finals on Thursday.

The Cavaliers are expected to be underdogs against either.

“We have an opportunity to play for a championship,” James said. “It doesn’t matter what the story line is going to be, it doesn’t matter if we’re picked to win or not. I’m the wrong guy to ask. I just like to compete.”

Jayson Tatum scored 24 points, Al Horford had 17 and Marcus Morris added 14 points with 12 rebounds for the Celtics, who were looking to return to the NBA Finals for the first time since 2010.

Tatum had a dunk over James with 6:41 left — staring down the Cavaliers star and bumping him with his chest — then followed it with a 3-pointer that gave the Celtics a 72-71 lead. But that would be Boston’s last basket for more than five minutes while Cleveland went on a 15-2 run to put the game away.

James embraced Horford and Tatum after the buzzer, then the Cavaliers donned celebratory hats and T-shirts before shuffling off the court to receive the Eastern Conference championship trophy.

It’s not the one they want.

James has been in the finals every year since 2011 — four with Miami, and now four straight with Cleveland.

This might be his weakest supporting cast.

He had to do it without Kevin Love — Cleveland’s only other all-star — who sustained a concussion in Game 6 and was replaced in the lineup by Jeff Green. Making his first start since the first-round opener against Indiana, Green scored 19 points and added eight rebounds — the star of James’ starless supporting cast.

“We said we want to do this for Kevin,” Lue said. “Kevin wanted to play, to be in a Game 7 situation like this in the Eastern Conference Finals, being an All-Star, being our second-best player, and he just wasn’t able to go. The guys picked him up, so now he has another chance when we get to the finals to be ready.”

The Celtics have had more time to get used to their injuries: Gordon Hayward has been out since the first game of the season, and Kyrie Irving has been sidelined since March. With the rookie Tatum and second-year Jaylen Brown, Boston established itself as the team of the future in the East.

“It was pretty incredible run by an incredible group of guys, and an absolute pleasure and privilege to be around them every day,” Stevens said. “We obviously have a good thing going.”

But the present still belongs to James.

Tip-ins

CAVALIERS: Shot just 2-of-17 from 3-point range in the first half, making three of their first 22 shots from long range before James and Green connected on back-to-back attempts midway through the third quarter.

CELTICS: Tatum is the first rookie to have 10 or more playoff games with at least 20 points since Kareem Abdul-Jabbar in 1970. Tatum’s 351 points this postseason was one short of Abdul-Jabbar’s record of 352.

** Paul Pierce, whose number was retired by the Celtics this season, cheered the team on from courtside.

Cavaliers 87, Celtics 79

CLEVELAND (87): James 12-24 8-11 35, Green 7-14 3-4 19, Thompson 4-4 2-3 10, Hill 2-6 2-2 6, Smith 3-8 3-5 12, Nance Jr. 1-2 0-0 2, Clarkson 0-2 0-0 0, Korver 1-6 0-0 3. Totals 30-66 18-25 87.

BOSTON (79): Tatum 9-17 4-4 24, Horford 7-12 3-3 17, Baynes 0-0 3-4 3, Rozier 2-14 0-0 4, Brown 5-18 0-0 13, Morris 5-14 2-4 14, Smart 1-10 2-4 4. Totals 29-85 14-19 79.

Cleveland 18 21 20 28 — 87
Boston      26 17 13 23 — 79

Fouled Out—Tatum. Rebounds—Cleveland 41 (James 15), Boston 42 (Morris 12). Assists—Cleveland 15 (James 9), Boston 18 (Smart 7). Total Fouls—Cleveland 21, Boston 20. Technicals—Boston coach Celtics (Defensive three second).

CAVALIERS

Percentages: FG .455, FT .720

3-Point Goals: 9-35, .257 (James 3-8, Smith 3-8, Green 2-9, Korver 1-6, Clarkson 0-1, Nance Jr. 0-1, Hill 0-2)

Team Rebounds: 11; Team Turnovers: 12 (15 pts.)

Blocked Shots: 4 (James 2, Green, Smith)

Turnovers: 12 (James 8, Hill 2, Nance Jr., Smith)

Steals: 2 (Hill, Smith)

CELTICS

Percentages: FG .341, FT .737

3-Point Goals: 7-39, .179 (Brown 3-12, Morris 2-6, Tatum 2-6, Horford 0-1, Smart 0-4, Rozier 0-10)

Team Rebounds: 10

Team Turnovers: 5 (5 pts)

Blocked Shots: 0

Turnovers: 5 (Tatum 4, Brown).

Steals: 6 (Brown, Horford, Morris, Rozier, Smart, Tatum)

A —18,624 (18,624). T — 2:18.

Officials — Kane Fitzgerald, Marc Davis, James Capers, Zach Zarba