What’s the biggest event of the year for biotech and big pharma? It’s ASCO. The American Society of Clinical Oncology kicks off its annual meeting Friday night in Chicago. Drug companies ranging from Pfizer (PFE) to Dendreon (DNDN) will present new research – and that research that could indicate whether their drugs are blockbusters or duds.

How closely is Wall Street listening? Two weeks ago, research leaked in advance of the meeting caused shares of ImClone (IMCL) to tumble. The reason: negative news about its flagship cancer medication, Erbitux.