HAMBURG -- The Italian surgeons who first used lumpectomy instead of mastectomy for small breast tumors are now doing breast-conserving surgery for larger tumors. The preliminary results of a study of 161 women conducted by the Milan Cancer Institute were announced at an International Cancer Congress here and published earlier this month in the Journal of the National Cancer Institute.

The study has rekindled an international debate about how much breast tissue should be removed without increasing the risk of a recurrence of malignancy.

In addition, the study has focused attention on whether doctors should treat small tumors -- either shrunken by chemotherapy or detected when they are tiny -- differently from big cancers.

This has been spurred, in part, by women demanding more cosmetically pleasing surgery and has led to approaches, like the Italian one, that try to save as much of the breast as possible, even in the case of large tumors.

The study's results, while promising, also raised concerns that they may be misleadingly positive.

Oncologist Gianni Bonadonna, who headed the study, said this is the latest step in an evolutionary process to end "mutilating surgery" that began about a century ago with the Halsted radical mastectomy, which removed the breast, lymph glands and chest muscles.

NCI officials point out that the Italian study lacks a control group, with which to compare results. The women in the Italian study all had big breast tumors, at least the size of walnuts. All received three to four months of chemotherapy to shrink the tumors. The 127 women whose tumors were reduced to smaller than 3 centimeters then had removal of just the tumor with a small margin of normal tissue.

Among 75 women whose surgery was at least a year ago, only one has had a recurrence, says Bonadonna. The standard measure of success is survival, which is determined by at least a five-year follow-up, preferably 10 years.

Bonadonna said his results show "that the classical indication for primary mastectomy can now be challenged by primary chemotherapy." Primary chemotherapy is defined as giving anti-cancer drugs as part of the initial treatment of cancer.

Even though chemotherapy shrinks the bulk of the tumor, surgeons still speculate that a few cancer cells may lurk in the periphery. Malignant cells that escape chemotherapy may incite another cancerous growth later.

In an editorial accompanying Bona- donna's article, former NCI director Vincent T. DeVita Jr. expressed concern about the preliminary nature of these results. Salvaging breast tissue may be crucial to some women, wrote DeVita, now physician-in-chief at the Memorial Sloan-Kettering Cancer Center in New York, but not at the expense of preventing a recurrence.

In the U.S., surgeon Bernard Fisher of the University of Pittsburgh has launched a randomized, controlled study using preoperative chemotherapy, lumpectomy and then postoperative radiotherapy for 800 women with large breast tumors.

Unlike the Italian study, Fisher's study includes two groups. Women are selected randomly to receive either the new treatment or surgery first, followed by postoperative chemotherapy. "We still don't know quite yet when you do chemotherapy and shrink tumors if they shrivel like a grape to a raisin," Fisher told the congress, "or wither like a dandelion leaving wisps of malignant cells."