Shares of AmSurg ( AMSG) were among the worst-performing health-related stocks Tuesday, falling 18% after the operator of surgery centers provided a third-quarter earnings preview below Wall Street's expectations.

When the company reports results on Oct. 25, it expects to post earnings of 30 cents a share, which doesn't include property losses of 2 cents to 5 cents a share from Hurricane Katrina. Analysts polled by Thomson First Call had been expecting earnings of 35 cents a share. During the third quarter, same-center revenue growth was 4%, below the 8% that AmSurg had expected. Of the 142 surgery centers operated by the company, 16 centers performed below expectations and below first- and second-quarter results, AmSurg said.

Looking ahead, AmSurg lowered its fourth-quarter same-center revenue growth expectations and revised its full-year guidance. The company now sees 2005 earnings from continuing operations of $1.18 to $1.21 a share and revenue of $390 million to $395 million, down from its prior forecast for earnings of $1.33 to $1.34 a share and revenue of $400 million to $420 million. Shares were trading down $5.18 to $22.87.

CancerVax ( CNVX) fell 42% after the drug development company and its partner, Serono ( SRA), said they would discontinue their phase III trial of Canvaxin. A data and safety monitoring board "found that the data are unlikely to provide significant evidence of an overall survival benefit for patients with stage III melanoma who were treated with Canvaxin versus those who received placebo," CancerVax said in a statement. In light of the discontinuation of the trial, CancerVax plans to cut its workforce to 80 employees from 183. Shares of CancerVax recently were trading down $1.23 to $1.69, while shares of Serono fell 13 cents to $16.37.

Shares of Cytogen ( CYTO) fell 13% after the biopharmaceutical company withdrew its full-year sales forecast. Because of weak sales during the third quarter, the company said that full-year sales would be below the $20 million that it previously forecast. During the third quarter, Cytogen recorded product sales of $3.5 million, which is below the company's internal expectations. Average gross margins, meanwhile, are still expected to be between 40% and 50%. Shares were trading down 51 cents to $3.44.

Lifeway Foods ( LWAY) rose 11% after the company offered a third-quarter sales estimate that pleased investors. The maker of kefir milk drinks said third-quarter sales came in at $5.2 million, up from $4.1 million a year earlier. For the first nine months of the year, the company posted sales of $14.9 million, up 23% from a year earlier.

"We have started to test market our kefir in club-store channels, restaurant food service, and most recently, an opportunity to offer kefir to an in-patient hospital healthcare setting based on the probiotic benefit that Lifeway Kefir may offer to populations undergoing antibiotic treatment," the company said.

"While most of these opportunities are limited, it offers Lifeway the chance to service new channels while advancing our shelf space and increased purchase orders in traditional grocer stores and natural food stores nationwide." Shares were trading up $1.33 to $13.18.

Shares of StemCells ( STEM) fell 3% after the company said it plans to sell up to $100 million in stock. In a shelf registration statement filed with the Securities and Exchange Commission, the company said that it plans to use proceeds from the offering to fund working capital and general corporate purposes. Shares recently dropped 19 cents to $5.32.

Other health-care volume movers included Pfizer ( PFE), up 20 cents to $25.49; Teva Pharmaceutical Industries ( TEVA), up $1.19 to $35.63; Merck ( MRK), unchanged at $27.25; Amgen ( AMGN), up $1.49 to $81.11; Elan ( ELN), up 1 cent to $8.43; UnitedHealth Group ( UNH), up $1.10 to $57.88; Johnson & Johnson ( JNJ), up 61 cents to $63.19; Abbott Labs ( ABT), up $1.53 to $44.01; Schering-Plough ( SGP), up 55 cents to $21.68; and Genentech ( DNA), up 73 cents to $86.95.