Sean Bartolucci went through almost 18 months of cancer treatment after a football-sized tumor was found in his stomach.

The 13-year-old from Camp Hill, Pennsylvania, underwent chemotherapy and radiation after doctors diagnosed him with neuroblastoma, which caused the formation of the large tumor in his abdomen.

The condition, which develops from immature nerve cells, often affects children who are five years old or younger. Some forms of neuroblastoma just go away on their own but some, just like in the case of Sean, require multiple treatments.

On Sunday, after receiving 20 rounds of radiation, five rounds of chemotherapy and a stem cell transplant, Sean marked the end of his treatment by running up the world-famous stairs outside the Philadelphia Museum of Art, which was featured in the Rocky films.

The idea to run a la Rocky Balboa was Sean's idea. He explained that they were in Philadelphia when he was diagnosed so this was among the first things that came into his mind.

Sean did the feat with about 30 of his friends and family who wore "Sean's a Fighter" T-shirts, and marked his victory at the top by raising his arms above him and shouting out "woo-hoo."

The young cancer survivor said that how his friends and family supported him just proves that he has an amazing community, family and friends that he can lean back on.

"He did it. He conquered it," said Sean's mother, Michele Bartolucci. "What a great way for him to celebrate, to know that we all are behind him and will continue to be."

The teenager's battle with the illness started in February 2014. Sean complained of a sore back one evening and collapsed the next morning prompting his parents to take him to the emergency room. Eight hours later, doctors told them that Sean had a tumor the size of a football in his stomach.

Sean was treated by doctors at the Children's Hospital of Philadelphia, which is about two-hours away from their home. He finished his treatments on June 6, Monday, but it took him until Sunday to build up his strength.

Sean will prepare to get back to being a regular teenager and enter eighth grade this fall. His mother said that he was actually doing online schooling to complete his seventh grade while undergoing chemotherapy and radiation.