SundayCelta Vigo     3-1  ValladolidReal Madrid  4-3     R SociedadMADRID - Barcelona coach Tito Vilanova admitted on Sunday that his cancer battle is not over and that he may be forced to once again step away from guiding the team’s thrilling pursuit of La Liga title.The 44-year-old underwent surgery for a second time on a tumour on a saliva gland on 20 December.He missed the away win over Valladolid but was back in the Camp Nou dugout on Sunday for the 4-0 derby victory over Espanyol which allowed Barcelona to go 11 points clear of Atletico Madrid and stay 16 in front of bitter rivals Real Madrid, who beat Real Sociedad 4-3."This is not over yet and there will be days that I can take training and others I can’t but I want the media to realise that this illness is mine and it is private even if I am a public figure,” said Vilanova."I would like to thank everyone for their support. This club has had a lot of knocks in the last couple of years but I always want to take the positive approach. What has happened to me could have happened to anyone.”Pedro Rodriguez hit a double with Xavi Hernandez and Lionel Messi also scoring in a rampant first half as Barcelona claimed a 17th win in 18 La Liga matches against just one draw.Barcelona’s win over Espanyol helped them extend their lead at the top of La Liga to 11 points after nearest challengers Atletico Madrid were held 1-1 by Real Mallorca.