Spencer, beloved Boston Marathon dog, dies after cancer battles

A golden retriever who became the biggest cheerleader during the Boston Marathon has died after multiple bouts with cancer.

According to local reports, "Spencer" died Friday. 

"Spencer, your spirit and determination inspired us all. We'll miss you, and are proud to call you a friend and forever the Official Dog of the Boston Marathon," the Boston Marathon organization posted on its Facebook page. 

Spencer was known to hold a "Boston Strong" flag along the marathon route for the past nine years as runners passed by. 

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He was then designated as the official dog of the 126th Boston Marathon by the Boston Athletic Association. 

In January, a giant portrait of Spencer was unveiled by the artist at Fairmont Copley Plaza, headquarters for Boston Marathon activity.

Spencer, The Boston Marathon Dog

Boston, MA - January 4: A massive portrait of the Boston Marathons famous dog icon and inspiration to people worldwide Spencer was unveiled by the artist at Fairmont Copley Plaza, headquarters for Boston Marathon activity. Spencer and his owner Rich

The longest-running annual marathon in the world, the Boston Marathon began in 1897 when 15 men drew a starting line in the dirt in Ashland and headed for the city to commemorate the first modern Olympic Games the previous year. In 1918, the format was modified to a relay due to World War I; the 2013 race was stopped when two bombs exploded at the finish line, several hours after the winners had finished but while many recreational runners were still on the course.

The field includes more than 30,000 recreational and charity runners, with as many as 1 million people lined up along the course trek from Hopkinton to Boston’s Back Bay.

The Associated Press contributed to this report. This story was reported from Los Angeles.