UMass (14-9, 7-3 Atlantic 10) matched its largest lead of 12 points at 48-36 with 11:04 to go. La Salle (13-10, 5-5) scored eight straight to close within 48-44, but the Minutemen kept their lead between four and eight points the rest of the way.
Lalanne finished with 11 points and 11 rebounds and Maxie Esho also scored 11.
Jordan Price led the Explorers with 30 points. His missed a 3-point attempt with 25 seconds left that would have closed the deficit to two. UMass made all four free throws from there.