The NBA said the game -- the second-to-last regular season contest for each team -- would not be rescheduled.
The cancellation means the Celtics, who hold the seventh seed in the Eastern Conference, and the third-seeded Pacers will finish their seasons with only 81 games played.
The NHL's Boston Bruins also postponed their scheduled Monday game against Ottawa after the afternoon blasts near the marathon's finish line.
Authorities said at least three people were killed and 130 more were injured in the two explosions.
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