Shares of

Antigenics

(AGEN) - Get Report

were among the best-performing health-related stocks Monday, rising 13% after the biotechnology company posted preliminary data from its phase III trial showing that Oncophage improved the survival rate in patients with metastatic melanoma by about eight months.

The drug improved median survival by more than 50% compared to patients who were subjected to a physician's treatment choice, which included therapies such as chemotherapeutics, biologic agents or surgery. While the treatment improved survival compared to other treatments, the company cautioned that the difference "has not achieved statistical significance at the time of this preliminary analysis." A final analysis is expected during the first quarter of 2006. Shares were trading up 63 cents to $5.64.

Universal Health Services

(UHS) - Get Report

rose 2% after the company agreed to acquire Keys Group Holdings for $207 million in cash. The acquisition is expected to add about $165 million in annual sales to Universal's results. The operational effective date, said Universal, is Oct. 1, 2005.

Universal Health also said that its board authorized an additional 2 million shares for repurchase, which will supplement the company's other buyback plan. Under the company's previous repurchase plan, the company still has 2.1 million shares remaining. The company was also granted authorization to buy its convertible debentures due 2020. Shares were trading up 76 cents to $46.94.

Shares of

Micro Therapeutics

( MTIX) rose 19% after its largest shareholder,

ev3

( EVVV), offered to buy the remaining 30% of the company that it doesn't already own. Ev3 would issue about 6.6 million shares to the company, representing a purchase price of about $7.90 a share, based on Friday's closing prices. The deal represents a 33% premium. "The combination of the two companies will facilitate the realization of efficiencies in sales and marketing as well as research and development," ev3's chief executive said in a statement. "In addition, the transaction will result in significant cost savings as redundant public company and other general and administrative expenses are eliminated." Shares of Micro Therapeutics were trading up $1.10 to $7.04, while shares of ev3 were trading down $1.34 to $15.91.

Patterson

(PDCO) - Get Report

rose 7% after Standard & Poor's said it would add the supplier of dental products to the

S&P 500 Index

after the close of trading today. Patterson will replace

Delphi

( DPH), which filed for bankruptcy over the weekend. Shares of Patterson were trading up $2.59 to $40.60.

Shares of

Nu Skin Enterprises

(NUS) - Get Report

rose 2% after the company increased its stock repurchase plan by $50 million. "We have a great deal of confidence in the future of our business," the company said. "We feel that the strength of our business, together with the products and initiatives announced during our recent global distributor convention, provides us with ample ammunition to drive continued growth."

Shares in the maker of personal care products tumbled last week after the company warned Wall Street that its third-quarter earnings and sales would be below expectations. The company attributed the shortfall to difficulties in China. Shares were recently trading up 29 cents to $17.49.

Other health care volume movers included

Pfizer

(PFE) - Get Report

, up 8 cents to $24.47;

Merck

(MRK) - Get Report

, up 86 cents to $26.71;

BioCryst Pharmaceuticals

(BCRX) - Get Report

, up $1.54 to $13.19;

Novavax

(NVAX) - Get Report

, up 42 cents to $2.53;

Schering-Plough

( SGP), down 14 cents to $20.34;

Johnson & Johnson

(JNJ) - Get Report

, up 33 cents to $61.67;

Amgen

(AMGN) - Get Report

, up 20 cents to $77.22;

Bristol-Myers Squibb

(BMY) - Get Report

, down 20 cents to $22.80;

Human Genome Sciences

( HGSI), down 8 cents to $8.70; and

Genentech

( DNA), up 39 cents to $81.54.