Boom was poorly positioned due to a lack of UCI points at the start, and did not manage to move up. He finished last on the lead lap, 7:15 behind race winner Mathieu van der Poel.
"What a day. I was suffering from start to finish," Boom said on Twitter. "My body is not used to this anymore. I need to work hard and rest hard [in the] upcoming weeks."
Boom plans to race the World Championships on the same circuit in January. He said after the race that his back was hurting. "It is a problem that only now rears its head during the race itself," he said according to Sporza.
"It's not abnormal. It's my first 'cross race, a technical course, up and down, it was so fast. You might work out in the field, but that is not the same as in a race."
Boom still needs to earn the selection to the Dutch squad for the World Championships, but said earlier this month that he had altered his return flight from Tour Down Under, where he will race with his Astana team, to make it back in time to race on January 31.