[7] For the 2006–2007 season, Boom asked and received special dispensation to ride the Dutch Elite Cyclo Cross championships and became Champion of the Netherlands.

[10] In November 2007, Boom won the Gerrit Schulte Trophy as the Dutch cyclist of the year for his two World Championship wins.

[17] In 2009 Boom won the Tour of Belgium after a strong performance uphill, and in the final Time Trial.

In the prologue of Paris–Nice he bested time-trial giants Jens Voigt, Levi Leipheimer, Alberto Contador and David Millar.

The stage was his first win of 2014 and came nine years to the day after the previous victory by a Dutch rider (Pieter Weening) in the Tour de France.

[22] There was some controversy at the beginning of the Tour, as Boom's cortisol levels were too low in his blood per MPCC rules to participate in a cycling event, but the Astana management decided to field him anyway.

[25] In May 2018, Boom was expelled from the Tour of Norway for aggression against Belgian rider Preben Van Hecke.

[27] In December 2019, Boom announced that he was retiring from road racing after being unable to find a contract for 2020, due to his Roompot–Charles team folding at the end of the season.

[3] He was a directeur sportif for UCI Women's World Tour team Liv Racing for the 2021 season and for SD Worx in 2022.