Not every patient who has a lumpectomy or a mastectomy also receives chemotherapy. How do oncologists decide that?
Well, you decide it on the basis of what the probabilities are that the cancer will come back, that the cancer has spread. What are the factors that we pay attention to? Well, the size of the cancer is very important. Tumors that are very small (less than one centimetre, less than half an inch in diameter) generally have a good prognosis. Tumors that are larger than one centimetre, particularly if they are larger than 2 centimeters, over an inch, are more serious. Tumors that have cells that look very wild — what we call poorly differentiated cells— a much higher chance to grow back. Tumors that penetrate into nearby small lymphatic or vascular channels tend to behave worse, and the presence of an abundance of certain genetic markers indicates that the cancer is more aggressive.
We know that cancers in young women tend to be more aggressive and they tend to come back more, and we know that we have to be more proactive and more aggressive in the treatment of younger patients. The so-called estrogen receptor and progesterone receptor, which have to do with the presence of compounds on the cell surface that indicate that the cells are sensitive to the female hormone estrogen also influence our course of therapy. The ones that have the receptors tend to have a slightly better prognosis.
So we put all of that information together and we try to come up with what is the probability of a cancer growing back in the future and recurring. Based on that probability we then decide whether chemotherapy is necessary.
So it might be necessary for someone who has a negative lymph node biopsy?
Oh, absolutely. Initially we used to apply chemotherapy when the risk of recurrence of the cancer was very high, so that we would use chemotherapy for patients who had a lump in the breast and had lymph glands under their arm that were involved. Under those circumstances the probability that the cancer will grow back with surgery alone is over 50 percent and chemotherapy reduces that risk fairly substantially.
As we were able to use drugs with a little better toxicity profile and as we were able to manage the side effects of chemotherapy better we started using chemotherapy in patients who have just a primary lump but no other invasion of lymph nodes or any other sign of spread. We now do so because by studying these patients we've learned that chemotherapy also improves the cure rate in those patients who have a lump in the breast without invasion of the lymph nodes.
Are there many patients at this stage receiving chemotherapy who shouldn't be receiving chemotherapy or for whom chemotherapy has no effect?
One of the factors that women use to try to decide whether to have chemotherapy or not for early breast cancer is determining what exactly will be the improvement. How can you quantify that improvement? My experience and some published reports indicate that if you ask women, you'll find that if the improvement in the chance of having the cancer come back exceeds 3 to 5 percent they will take it.
Now what do we mean by 3 to 5 percent? Well, if you take a hundred women with breast cancer and if the probability that the cancer will come back for each of those women is, let's say, 15 percent, and if you can lower that probability from 15 percent to 10 percent with chemotherapy, women will decide to take it. What does that mean? Well, it means that you're going to have to treat a hundred women to help five.
Do you find that's a great shame?
As a medical oncologist I see patients who have cancer and who need treatment, and my job is to provide everything that I have available to reduce the odds that that person is going to die of cancer. My job is to make sure that the person understands what the options are, and that we use those options wisely so that we improve the cure rate and maintain the quality of life and the function of that person.
When you're facing somebody with primary breast cancer, perhaps with a small lump in the breast and no lymph node involvement, you can say, well, the probability that this person will be cured with surgery alone without chemotherapy is 70 percent, and the probability is about 30 percent that this cancer will come back.
We have treatments such as chemotherapy that will improve that chance of recurrence from 30 percent down to 20 percent. We have no way of telling whether that particular person is the person who will benefit from it, so my question to that woman is "there are two buses leaving town. The women in one bus are going to have a 20 percent chance of recurrence and the women in the other bus are going to have a 30 percent chance of recurrence. Which bus do you want to take?"
So the issue is not as much about the fact that how non-specific and how toxic it is. The issue is what I face every day: this is what we have today, this is the best we can do today. I'm sure we'll be doing much better in ten years, but this is what we have to do now and that's my job: to help women make a decision as to what's the best choice today.