he National Cancer Institute has been bullied by Congressional conservatives into revising its best judgment on whether abortion increases the risk of breast cancer. Unless the institute can summon the courage to express its true views, it will be severely damaged.

Researchers have long debated whether abortion increases the risk of breast cancer, possibly by altering hormones and tissue development in the breast. A fact sheet distributed by the institute last March noted that studies conducted before the mid-1990's produced inconsistent results but that subsequent studies generally found no association between abortion and breast cancer. The American Cancer Society reached the same conclusion.

Those judgments were anathema to anti-abortion groups, which have been trying to scare women away from abortion by raising the specter of breast cancer. A group of 28 anti-abortion members of Congress complained to Tommy Thompson, secretary of health and human services, that the institute's formulation was "scientifically inaccurate and misleading." So in June, the institute removed the fact sheet from its Web site and later replaced it with a statement that some studies have found an increased risk of cancer while others have not. That statement, while technically accurate, is such an egregious distortion of the evidence that one can only hope it is an interim statement, as some staff members suggest, not a final surrender.

The institute plans to address the issue at a conference on pregnancy and breast cancer in February. If the experts at the meeting agree that there is no link between abortion and breast cancer, the institute will have no excuse to suppress the information. It will have to issue a new fact sheet or admit it can no longer provide objective guidance on matters that inflame social conservatives.