February 9, 2011
Implications of Study on Breast Cancer

An article on Wednesday described how a routine procedure for the treatment of early breast cancer — the surgical removal of cancerous lymph nodes from the armpit — has been found unnecessary for many patients. The finding turns 100 years of standard medical practice on its head. The author of the article, Denise Grady, answered questions online from readers about the finding and its implications. More at nytimes.com/science.

Q The study findings apply to 20 percent of breast cancer patients. What about the other 80 percent?

A The figure refers to 20 percent of all the newly diagnosed cases of invasive breast cancer each year in the United States — it does not include noninvasive breast cancer, or D.C.I.S., ductal carcinoma in situ. The total is about 207,000, so 20 percent is roughly 40,000 women. That is about how many women would match those in the study, in terms of tumor status, affected lymph nodes and course of treatment.

As for the other 80 percent, we need to look at how many women get a breast cancer diagnosis at various stages. The figures from the American Cancer Society indicate that 60 percent of all patients have “localized” breast cancer. That means they do not have affected lymph nodes. They do not need extensive axillary dissection, as lymph node removal is known.

An additional 33 percent of women have “regional” disease, meaning that the cancer has reached lymph nodes. These are the patients who might match those in the study.

By the estimate of Dr. Armando E. Giuliano, the lead author of the study and the chief of surgical oncology at the John Wayne Cancer Institute at St. John’s Health center in Santa Monica, Calif., about two-thirds of these women will match the study criteria and one-third will not. So for that one-third — about 10 percent of breast cancer patients over all — node dissection might be needed. An additional 5 percent of all patients have “distant” disease at the time of diagnosis, meaning the cancer has already spread to organs or bones. I don’t know if lymph node surgery is of use or benefit to women whose disease is already advanced. In the remaining 2 percent of cases, the stage of the disease at diagnosis is not known.

Q Why are the study findings said to apply only to women who have whole-breast irradiation, and not partial breast irradiation?

A Only whole-breast irradiation hits part of the armpit, and therefore some of the lymph nodes. This is what the women in the study received, and researchers think it may have wiped out any cancer in the nodes that were left behind. They say they are also unsure about whether the findings would apply to women who have irradiation while lying prone, on their stomachs. In that position, the radiation may not reach the armpit.

Q Which women still must have their lymph nodes dissected?

A Surgeons say that the lymph nodes must come out if they are big enough to feel or show up as cancerous on imaging. Surgeons will also remove nodes if there are three or more positive sentinel lymph nodes (sentinel lymph node biopsy is described in the article).

Surprises can also turn up in the operating room, doctors say. Occasionally, the sentinel node biopsy will give a false-negative result, which means failing to find cancer even though it is present. That can happen if, for instance, the sentinel node is very cancerous and the lymphatic vessels that feed it are choked off and do not pick up the dye. Then, the dye may go to a different node, one that does not have cancer. Knowing this is possible — and knowing that the sentinel node biopsy, though highly reliable, is not infallible — surgeons look and feel around in the armpit carefully during the operation and make judgment calls about what to remove and what to leave alone.

Q How do these findings apply to women who have a genetic predisposition to breast cancer?

A Dr. Monica Morrow, an author of the study and chief of the breast service at Memorial Sloan-Kettering Cancer Center in Manhattan, replied: “Genetic breast cancer doesn’t influence how we treat the nodes. Due to the increased risk of second breast cancers, many of these women chose mastectomy. Women with mastectomy require axillary dissection if the nodes are involved.”

Q From what I understand, removing even only one or two lymph nodes can result in chronic swelling of the arm. How certain is it that taking fewer nodes will result in a measurable reduction in the risk of developing lymphedema?

A There is still a risk of lymphedema even after only a few nodes are taken for sentinel biopsy, but the risk is much lower than when many nodes are removed.

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