A panel of experts says removing a cancerous tumor in the early stages of breast cancer gives as good a survival chance to women as more radical surgery in which the entire breast is removed. Mastectomies, in which the entire breast is removed, and lumpectomies, in which only the tumor is removed, both give ``excellent'' results for Stage I and Stage II breast cancer, the panel said. The committee of 15 experts was assembled by the National Institutes of Health to consider research on the survival of women with early stages of breast cancer and to develop a consensus on what therapy should be used to treat the disease. ``The therapies appear to be equivalent in survival,'' said Dr. William C. Wood, a Harvard Medical School surgeon and chairman of the committee. ``We believe it is preferable to preserve an organ.'' Mastectomy is still the most commonly used therapy for early stage breast cancer, Wood said. A lumpectomy is followed with radiation therapy, and Wood said some patients choose mastectomy because they ``prefer to lose a breast instead of have six weeks of radiation therapy.'' In its report, the committee said surgery in which the breast is saved, or conserved, ``is an appropriate method of primary therapy for the majority of women with Stage I and II breast cancer, and is preferable'' because the breast is preserved and the survival chances are the same as for mastectomy. Wood said that both mastectomy and lumpectomy involves the removal of nearby lymph nodes. If these nodes are cancer-free and the primary tumor is smaller than one centimeter, both methods of treatment have about a 90 percent chance of cure. About 150,000 American women will be diagnosed with breast cancer this year, the committee report said. Between 75 percent and 80 percent of this group will have Stage I or Stage II disease, and about two-thirds of these will have cancer-free lymph nodes. Stage I and II cancers have not spread beyond the breast and lymph nodes. But just how to treat this early-stage breast cancer long has been controversial. Traditionally, the preferred treatment has been a radical mastectomy in which the entire breast and much adjacent tissue is removed. During the past two decades, there have been a number of studies comparing the survival results of less extensive breast surgery, including lumpectomy. The committee found that, based on the studies, survival rates are virtually the same for the two types of therapy. The experts said the picture was less clear for follow-up treatment using chemotherapy or a drug that blocks the hormone estrogen. The studies show a trend that may suggest an advantage in taking the follow up or adjuvant therapy, but the committee said the drugs may be toxic or degrade the patient's quality of life. For patients with very small primary tumors _ one centimeter or less _ adjuvant therapy is not required, the committee said. The committee also said that the use of lumpectomy should be based on an individual evaluation of each patient and with the full understanding by the patient of all the options. Lumpectomies are not appropriate for all Stage I or II patients because of the size of the breast, or the distribution of tumors or calcified lumps within the breast, the committee said.