BTG has given a bullish outlook for its annual performance after a strong start to the year, with the specialist healthcare company entering the second half "confident of continuing this strong momentum".In spite of adverse currency exchange movements, the group expects revenues to be around the top end of its guidance range of £330m-345m in the year to 31 March 2015, up from £290.5m the previous year."We have made good progress across the business during the first half of the year," said chief executive Louise Makin.During the first half to 30 September, BTG's Interventional Medicine division was helped by good growth in Therasphere and Ekos, its liver cancer and blood clot treatments which were acquired last year.First commercial sales of varicose vein treatment Varithena were also recorded in August after its launch in the States, while commercial launch preparations are under way in China for DC Bead, used in the embolisation of malignant hypervascularised tumours.The Specialty Pharmaceuticals business also delivered a strong performance, BTG said, helped by continued growth of Digifab and Voraxaze and sales of Crofab.Increased royalties from Johnson & Johnson's treatment for advanced prostate cancer, Zytiga, also helped to lift licensing revenues.The stock was up 1.3% at 728.31p in early trading on Monday.