It was a day tipped for the breakaway, and one that was especially hard. Stage 4 of the Tour de France headed from Carcassonne to Foix over four categorised climbs and through extreme heat that saw the UCI implement emergency measures.The 2019 world champion Mads Pedersen sprinted to win the stage, and he was closely followed by Uno Xs Torstein Tren, who was treated for cancer in 2022 and now leads the general classification.It feels unreal and you dont really understand whats going on, Tren said after taking the yellow jersey today.When I went into the breakaway, I was not believing until I came to the last climb. And [then] I understood that the legs are pretty good and the gap is pretty big, Tren said.That gap means Tren now leads the general classification by 7 minutes and 53 seconds from Tadej Pogaar and Jonas Vingegaard who are tied on the same time.Although he is not an overall favourite for the Tour de France, Trens palmars suggests he could hang onto yellow through the coming days. The 30-year-old climber led the 2025 Vuelta a Espaa for four stages and finished ninth overall.Trens cancer diagnosis followed an abnormal doping control test that revealed indicators of the disease. Anti-doping authorities contacted the Norwegian after the tumour marker Human Chorionic Gonadotropin was found in his sample. Doctors found a 15mm tumour in a testicle and surgery meant Tren didnt need to undergo chemotherapy.Trens performance on stage 4 is also poignant for Uno-X Mobility. Tren started his career with Uno-X Mobility in 2016 before moving to Bahrain-Victorious in 2022.He then returned to Uno-X Mobility in 2023, the first year the team was asked to participate at the Tour de France.Remarking on Trens performance on stage 4 and yellow jersey, Uno-X Mobilitys sports director, Christian Andersen, said: Its the biggest day weve had so far. Its outstanding.Todays stage also saw the UCI soften its rules around feed zones to ensure riders stay hydrated as temperatures hit 40C.