CHICAGO - Scientists reported promising gains Monday for treating colorectal cancer that has spread to the liver, showing that chemotherapy before and after surgery to remove liver tumors can help keep the disease in check.

The study is the first to scientifically test an approach that many doctors have tried for patients with advanced colon and rectal cancers.

"It justifies what some of us have already been doing" and shows that aggressively treating patients with limited spread of colorectal cancer is reasonable, said Dr. Jeffrey Meyerhardt, a cancer specialist at Dana Farber Cancer Institute in Boston.

About 1 million people worldwide develop colorectal cancer each year, including more than 150,000 in the United States, where it is the third most common major cancer. In up to half of all patients, the disease spreads after initial treatment to the liver. For many cancers, spread to the liver means the disease has also spread elsewhere, is incurable and surgery isn't an option.

But with colorectal cancer, sometimes the disease spreads only to the liver, and surgery to remove these growths increasingly is being attempted, said Dr. Neal Meropol, director of the gastrointestinal cancer program at Fox Chase Cancer Center in Philadelphia. Even so, recurrence is common, and only about 30 percent of patients who have this surgery survive five years.

In the new study, 42 percent of patients who got chemotherapy before and after the liver surgery had no recurrence after an average of three years, versus 33 percent of patients who had surgery alone.

The good results mean the approach could become standard treatment for these patients, said Dr. Bernard Nordlinger, the lead author and a cancer specialist at Ambroise Pare Hospital in Paris.

Nordlinger presented the results in Chicago at the American Society of Clinical Oncology's annual meeting.

A separate colorectal cancer study presented Monday showed the targeted cancer drug Erbitux can modestly improve survival when added to standard chemotherapy in patients whose disease has spread. Patients who got Imclone Systems Inc.'s drug survived an average of 8.9 months without disease progression versus eight months for those who got chemotherapy alone.

"Although we would all love to have huge breakthroughs that would revolutionize cancer treatment, those are few and far between," said Northwestern University's Dr. Al Benson III. Instead, cancer treatment advances typically come in smaller but important steps like the colorectal cancer studies presented Monday, which over time lead to real progress, Benson said.

The chemotherapy-plus-surgery study involved 151 patients who had both treatments and 152 who had surgery alone. The chemotherapy used was a commonly used combination of drugs called oxaliplatin leucovorin fluorouracil.

Complications, including diarrhea and reduced amounts of disease-fighting white blood cells, were more common in chemotherapy patients but were still within an acceptable range, Nordlinger said.

A separate study presented Monday involved primary liver cancer - disease that originates in the liver rather than spreads there. Researchers said they have found the first drug that improves survival for liver cancer patients - a breakthrough that likely will become standard treatment.

Those results occurred in patients with advanced liver cancer treated with the drug sorafenib, or Nexavar, which is marketed by Bayer Pharmaceuticals Corp. and Onyx Pharmaceuticals Inc. to treat advanced kidney cancer.

The companies are expected to seek U.S. approval this summer for treating liver cancer with the drug.