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Posted on May 22, 2014 at 4:01 PM

[The New York Times]Many men with an early sign of a prostate cancer relapse can safely wait before starting hormone therapy, avoiding side effects without shortening their lives, according to the results of a study released on Wednesday.

Dr. Clifford A. Hudis, president of the American Society of Clinical Oncology, said the study “certainly does not provide evidence that you have to rush in with treatment, and it does provide comfort if you choose for any reason to withhold treatment at the beginning, that you’re probably not risking much.”

Dr. Hudis spoke in a telephone news conference on Wednesday in advance of the society’s annual meeting, which begins on May 30 in Chicago. Abstracts of more than 5,000 studies were made available on the society’s website on Wednesday.

The studies are of interest not only to doctors and patients but also to Wall Street and drug companies. A lung cancer drug being developed by AstraZeneca, for instance, shrank tumors in about half the patients in an early-stage trial; that could bolster AstraZeneca’s argument that its future is bright as a stand-alone company — but could also increase Pfizer’s desire to acquire it.

The prostate cancer study involved men who had undergone surgery or radiation therapy aimed at curing their disease but then had a rise in the level of prostate-specific antigen, which is a marker for the disease, in their blood without any symptoms or evidence from scans that the cancer had returned. Researchers said that about 60,000 American men a year find themselves in this situation.

The typical next step would be to take drugs to block the hormone testosterone, which fuels prostate tumor growth. But such therapy can cause side effects like hot flashes, loss of libido and weakening of muscles and bones.

The study followed about 2,000 men in a national patient registry who had such “P.S.A. relapses.” Some chose to get hormone therapy immediately. Others waited at least two years, or until there were other signs of a relapse.

There was basically no difference in five-year and 10-year overall survival rates or in the death rates from prostate cancer specifically, said Dr. Xabier Garcia-Albeniz, a research associate at the Harvard School of Public Health and the study’s lead author.

The major shortcoming is that the men were not randomized to receive either immediate or delayed treatment, said Dr. Garcia-Albeniz. Men who chose immediate treatment might have been different in some way that could have influenced the survival results, though efforts were made to correct for known differences.

Dr. Julio M. Pow-Sang, chairman of genitourinary oncology at the Moffitt Cancer Center in Tampa, Fla., said the results were nonetheless important.

Many doctors already feel comfortable waiting, said Dr. Pow-Sang, who was not involved in the study. But patients, he said, “understandably get very anxious. The first natural reaction is wanting to do something.”

As was true last year, much of the attention at the cancer conference in Chicago will be on immunotherapies, which enable the body’s immune system to attack tumors.

One class of these drugs, which inhibit the activity of an immune-cell protein called PD-1, have shown remarkable results in shrinking tumors in early testing as treatments for melanoma, lung cancer and kidney cancer.

This year there will be some early results on whether the drugs can work against bladder cancer and head and neck cancer. About half the bladder-cancer patients who received a Roche immunotherapy drug in a tiny study experienced significant tumor shrinkage, according to one of the abstracts.

Companies are also teaming up to test combinations of these types of drugs, with two such deals announced on Wednesday.

Bristol-Myers Squibb will test its PD-1 inhibitor, nivolumab, in combination with varlilumab, a drug from Celldex Therapeutics that stimulates the immune system in a different way.

AstraZeneca will test its drug MEDI4736, which blocks a protein related to PD-1, in combination with a drug from Incyte that is called INCB24360.

MEDI4736 is one of the main assets AstraZeneca has that is of interest to Pfizer. Another such asset is AZD9291, which is being developed to treat lung cancers that have become resistant to Tarceva and similar drugs.

In an early-stage study testing various doses of AZD9291, 51 percent of 177 patients experienced significant tumor shrinkage, the lead investigator, Dr. Pasi A. Janne of the Dana-Farber Cancer Institute, said in the news conference.

The response rate was 64 percent for the 89 patients whose resistance to Tarceva and the other drugs was caused by a particular genetic mutation in their tumors.

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