Thousands of cancer doctors - and a good number of investors - will converge in Orlando this weekend to discuss the latest developments in cancer treatment, and the impacts on drug makers like Roche Holding AG (RHHBY), Eli Lilly & Co. (LLY) and OSI Pharmaceuticals Inc. (OSIP).

The annual meeting of the American Society of Clinical Oncology, running Friday to Tuesday, follows a data deluge of more than 4,000 cancer studies released two weeks ago. Some of that data will be further detailed, while the most notable studies have been withheld as "late breakers" that will be orally presented by researchers.

Those notable studies will highlight advances in earlier treatments for lung cancer and new research in gastrointestinal cancer at a time when healthcare reform looms over drug makers and the high cost of cancer treatments is becoming an increasingly hot topic.

The meeting also brings the long-awaited data for Avastin, made by Roche's Genentech unit, in its use in the so-called adjuvant setting, when it is used to prevent relapse following surgery in colorectal cancer.

Although the study failed to reach its main goal, as announced in April, adjuvant usage of Avastin in many cancer area remains the key long-term growth driver for the drug.

Furthermore, the Avastin adjuvant data may provide some insight for Roche investors who worry the Swiss drug maker overpaid in its $46.8 billion Genentech buyout in April. Roche has played down the role of the trial in the deal, but it rushed to complete the deal before the cooperative conducting the trial released the data.

Since the deal, the data is less crucial for U.S. investors, but observers will be looking to see the drug's level of activity in the patients to gauge its possible success in other trials or as an earlier treatment for longer periods of time in advanced patients.

Avastin, already approved to treat advanced breast, lung, brain and colorectal cancer, had 2008 U.S. sales of $2.69 billion.

Also, the degree of effectiveness could provide insights into drugs that act on similar targets to Avastin, such as Pfizer Inc.'s (PFE) Sutent and Nexavar, sold by Onyx Pharmaceuticals Inc. (ONXX) and Bayer AG (BAYRY).

Genentech and Roche also will get attention for key data coming on Tarceva, sold with OSI Pharmaceuticals, as a treatment for advanced lung cancer and pancreatic cancer.

The drug, along with Lilly's Alimta, is being tested for use as maintenance therapy in lung cancer - when it is given after chemotherapy but before new tumor growth.

In the earlier ASCO data release, a Tarceva study called Saturn showed it prolonged progression-free survival, or PFS, but the median measure of that benefit was only one week.

Although those results were largely disappointing, Wall Street has high expectations for the Atlas study, which uses Tarceva in conjunction with Avastin as a maintenance therapy. Notably, the trial was halted early because of its effectiveness.

Tarceva had 2008 U.S. sales of $457 million and worldwide sales of $1.12 billion. Earlier this month, OSI Chief Executive Colin Goddard projected Tarceva's maintenance use adding more than $500 million to annual U.S. sales after its projected label expansion in 2010.

Alimta, Lilly's drug, showed a PFS benefit of two months at last year's ASCO as a maintenance therapy in lung cancer, but this year it will provide data on overall survival, the ultimate measure of benefit in lung cancer.

Other key data expected to be presented include a late-stage study that shows Genentech's Herceptin, a drug approved to treat a certain type of breast cancer, is effective in treating gastric cancer. The magnitude of the effect won't be known until the meeting, but could eventually provide another market for Herceptin, which had 2008 U.S. sales of $1.4 billion.

Another pair of studies examines the recurrence risk in breast cancer patients using tamoxifen, a form of chemotherapy, along with a certain class of antidepressants that are used to reduce hot flashes.

-Thomas Gryta; Dow Jones Newswires; 201-938-2053; thomas.gryta@dowjones.com