The 12 heures contre le cancer - Ludres is a 12-hour trail and walking event held at the Plateau des Loisirs in Ludres, near Nancy. Organized by the local A.L.T.E.R. association, it takes place on a Saturday in March from 8 a.m. to 8 p.m. The event offers five formats: a continuous lap challenge, solo backyard running, team backyard relay, a 13.5 km nature race, Nordic walking, and a popular walk.
The main loop covers 6.7 km with 268 m of elevation gain, following forest and meadow paths around Ludres and Messein. In the backyard races, participants start a new lap every hour and can complete up to 12 laps. Missing an hourly start means waiting for the next one, not disqualification. Teams consist of three runners who manage their own relays. The shorter race options broaden participation: the nature race is 13.5 km with 280 m of elevation gain, and both walking routes are 10.5 km with 150 m of elevation gain. The event emphasizes its charitable cause by reducing participant favors to allocate more profit to La Ligue contre le cancer.