The Italian sprinted to the line ahead of team-mate and leadout man Sonny Colbrelli and Mauro Richeze of Team Nippo.
Modolo, a part of the Italian Olympic team that returned home empty-handed, made a gesture at the finish line to express his frustration.
“We are young - we get angry when we do bad things," he said. "I’ve been criticised and I wanted to show that I’m not finished.
"At the Olympics it didn’t seem that the Italian national team rode so badly and so didn’t deserve such criticism."
He added: "We did everything perfectly, even if the finale was not easy since no one cooperated; that’s why I threw myself into an escape on the last lap."