The tumble in share prices for biotechnology stocks has created some buying opportunities, with drugmakers Celgene Corp (CELG.O) and Gilead Sciences (GILD.O) poised for a 30 percent rise over the next year, Barron’s said. Celgene, which specializes in treatments for a blood plasma cell cancer called myeloma, could see double-digit growth for its Revlimid drug for years to come, with significant growth potential from overseas, Barron’s said.