PET Scan (Positron Emission Tomography)

There are a variety of physician preferences for following tumors during therapy, but the approach used in most clinical trials is a standard CT scan every other cycle of chemotherapy. There is increasing use of PET scanning, but this is experimental, expensive, and there is a high risk of getting misleading information from a PET that could result in inappropriate changes in therapy. There are a variety of physician preferences for following tumors during therapy, but the approach used in most clinical trials is a standard CT scan every other cycle of chemotherapy. There is increasing use of PET scanning, but this is experimental, expensive, and there is a high risk of getting misleading information from a PET that could result in inappropriate changes in therapy.

I also had it about a week after the sentinel lymph node biopsy was positive with cancer. Wow! Those early days are such a blur! Looking at my calendar, I see that I had a PET/CT about a week after my surgery and about two weeks before I began chemo. A few cancer cells had been found in my lymph nodes, and my doctors wanted to see whether my cancer had spread to other, more distant parts of my body, like my liver or bones.

In my case, the PET/CT showed a lesion on my liver that was thought to be a possible metastatic deposit. I was very upset. It seemed as if every time I’d gone to the doctor, I’d gotten more bad news. A month earlier, I had been a seemingly healthy woman in the prime of her life. Now I might be facing metastatic cancer.

Since the lesion on my liver was in an area that was difficult to biopsy without major abdominal surgery, an MRI was ordered to examine it in greater detail.

Then a liver specialist looked at all the images, and he said he was absolutely certain the lesion was a hemangioma, a harmless cluster of blood vessels—like a birthmark—that many people have. He said that after I had completed chemotherapy, I should have another MRI to see whether the lesion had changed. If it had shrunk, it was indeed cancer and the chemo had been effective in reducing its size. If it had grown, it was cancer but the chemo had failed to treat it. If it stayed the same size, it was not cancer.

Fortunately, the lesion stayed the same size. The liver specialist was right. It was a harmless hemangioma.

I would reinforce Dr. Moore's answer that not all breast findings need an MRI. There is no way that any of us can tell based on the information provided whether or not an MRI or other imaging will be helpful or necessary in this case - an understanding of the patient's clinical situation as well as review of the mammograms and any available pathology reports is necessary. In general, calcifications do not show up on MRI. There is no question that there are cancers that will show up on MRI that are missed by other imaging, but again each case needs to be properly evaluated before a blanket recommendation for MRI is made. There is no best imaging test for the breast, but that also does not mean that every test should be done in every person. Calcifications are very commonly seen in the breast. More than 50% of all mammograms performed have calcifications. The vast majority of them are related to benign or "normal" things. Surgery is one of the things that can produce calcifications. According to a recent Medscape article "high quality mammography is the best diagnostic tool for the identification of breast calcifications." When we interpret mammograms we characterize calcifications in terms of their their shape, number, distribution and size. We then categorize them as normal, benign, probably benign, or suspicious. Suspicious calcifications are biopsied, even though there is no palpable lump, or breast pain, or any other findings.

In one study 300 biopsies were performed on suspicious calcifications and only 100 of them were cancers. So even those that look suspicious are not always related to cancer.

MRI of the breast is a very sensitive test that is not always specific. If you have a lump that is palpable, or is seen on mammography or ultrasound, MRI may help. It can also find unsuspected small lesions as part of preoperative planning. MRI is not good at looking at calcification. Could MRI show you something really small that is in the area of the calcifications that is not seen on other tests? Possibly, but if the calcifications are in the area of the surgery MRI might be abnormal anyway, and more difficult to interpret.

Every case is different and every medical decision is made in the context of that patient's personal and family history, physical findings,and all imaging results. Patients are best served when they have a doctor who listens to them and whom they trust. Decisions are then made together. Unfortunately medicine is not an exact science, and our knowledge is still incomplete, in spite of the advances we have made.