Updated from 2:21 p.m. ESTShares of Dendreon ( DNDN) were among the worst-performing health and pharmaceutical stocks Tuesday, slumping 26.7% after the company's final analysis from a three-year survival study of Provenge disappointed investors. Provenge, the company's investigational immunotherapy for the treatment of advanced prostate cancer, "did not show a statistically significant delay" in the study's primary endpoint, time to disease progression. Analysis of the D9902A study showed no significant delay in the overall group or in the Gleason score subgroups, the company said. The study's secondary endpoint, overall survival in the intent-to-treat patient population, "indicated that both the survival rates and the median survival benefit compared with placebo are similar to the results observed in the final three-year survival analysis of the D9901 study," the company said. That study showed a survival benefit. The mixed results prompted Needham & Co. to cut its rating on the stock to buy from strong buy. Shares traded down $2.77 to $7.62. AmerisourceBergen ( ABC) rose modestly after the company reaffirmed its first-quarter and 2005 earnings outlook. The pharmaceutical services company expects first-quarter earnings of 60 cents to 65 cents a share. Analysts polled by Thomson First Call are expecting earnings of 63 cents a share. Full-year earnings are expected to be between $4 and $4.10 a share, above the $3.89 a share that analysts had been expecting. AmerisourceBergen expects 2005 operating sales growth to be flat, reflecting the loss of two large customers during 2004. Shares traded up 14 cents to $58.04. Shares of Genentech ( DNA) fell 6.9% after the company posted soft fourth-quarter earnings and guided lower for 2005. Excluding items, the biotech company earned 21 cents a share in the fourth quarter on sales of $1.32 billion. Analysts had been expecting earnings of 22 cents a share on sales of $1.3 billion. Looking ahead, the company expects 2005 earnings to grow by more than 25%, implying earnings of about $1.04 a share. Analysts, however, had been expecting earnings of $1.11 a share. Shares traded down $3.73 to $50.70. MGI Pharma ( MOGN) fell 11% after the company warned that 2005 earnings before interest and taxes would fall below previous guidance. The company now expects earnings before interest and taxes of $62 million, below its previous guidance of $75 million. Sales, meanwhile, are expected to be about $285 million, up from previous guidance of $280 million, but just below analysts' expectations of $287 million. Shares traded down $2.96 to $23.95. Other health care movers included Aastrom Biosciences ( ASTM), up 20 cents to $2.58; Pfizer ( PFE), down 29 cents to $26.15; StemCells ( STEM), up 14 cents to $5.25; Biopure ( BPUR), down 1 cent to 56 cents; Amgen ( AMGN), up 14 cents to $63.78; Merck ( MRK), down 33 cents to $31.17; Schering-Plough ( SGP), up 6 cents to $21.31; and Bristol-Myers Squibb ( BMY), down 38 cents to $24.60.