SALEM ? The 18th annual North Shore Medical Center Cancer Walk, a benefit event that has raised more than $13 million since its inception to fight cancer, gets under way Sunday, June 22.The 6.2-mile route begins and ends at Salem Willows Park. Registration opens at 7:30 a.m. and the event has a rolling start beginning at 8 a.m.Organizers note that registration is easy. Anyone interested in participating by walking or making a donation can register online at www.nsmccancerwalk.org or call toll-free 866-296-6900. Walkers will find an array of entertainment and refreshment breaks along the route.Jennifer Flanagan of Marblehead, this year’s event spokesman, said the average walker raises $100 or more, and participates with friends, relatives and cancer survivors.The walk is the North Shore’s largest single-day fundraising event. This year, all proceeds will directly benefit the expansion and relocation of the NSMC Cancer Center in Peabody to the Mass General/North Shore Cancer Center, slated to open in Danvers in 2009, according to medical center spokesman Janet Zipes.The new state-of-the-art oncology facility will build on a decades-old collaboration between the medical center and Mass General Hospital, while significantly deepening the level of integration between the two institutions, she said.The Danvers center is being designed to offer comprehensive and coordinated medical, surgical, and radiation oncology care in a community-based environment, Zipes said.