By David Russell, reporter at OptionMonsterNEW YORK ( TheStreet) -- Omnicom ( OMC) has been consolidating after a run to its recent highs, and now some investors are positioning for a breakout. optionMONSTER's Heat Seeker tracking system detected the purchase of more than 7,800 October 45 calls for 70 cents to 90 cents. Volume was more than 135 times open interest in the strike. OMC rose 0.4% to $39.82 Tuesday and is up 8% in the past month. The advertising stock has been rallying since its last earnings report on Feb. 10, when revenue fell less than expected and management predicted top-line growth in the second half. Omnicom has spent the past five sessions pushing against the same $40 level where it peaked late last year. Tuesday's call-buyers are apparently betting the stock will push through that level by late spring. OMC must rally at least 15% by expiration for the trade to turn a profit. Calls overall outnumbered puts by a bullish 50-to-1 ratio, and total options volume was 39 times greater than average. At the time of publication, Russell had no positions in Omnicom.