TORONTO, March 30 (Reuters) - Canada's main stock index pulled back from a one-month high on Thursday as deal-related news pressured shares of Cenovus Energy Inc CVE.TO and Canadian Imperial Bank of Commerce CM.TO .
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE unofficially closed down 78.87 points, or 0.50 percent, at 15,578.76. Five of the index's 10 main groups ended lower.