CHICAGOMagnetic resonance imaging (MRI) was able to find tumors
in two thirds of 47 patients with stage II or III occult primary
breast cancer with a high degree of sensitivity, avoiding mastectomy
in nearly half of the women, Elizabeth Morris, MD, reported at the
85th Annual Meeting of the Radiological Society of North America (RSNA).
Occult primary breast cancer is relatively rare, accounting for less
than 1% of all breast cancers. It is defined as carcinoma that has
metastasized to the axilla or other sites of the body in the absence
of mammographic or physical findings of disease in the breast.
Patients with stage II or III occult disease (localized metastatic
adenocarcinoma confined to the axilla) may be treated with
ipsilateral radiotherapy. However, many institutions have chosen
mastectomy as first-line therapy because of concern about high
recurrence rates with radiotherapy, Dr. Morris said. Patients with
stage IV occult disease (distal metastatic adenocarcinoma) typically
are treated with chemotherapy.
In this series of patients who had been followed over a period of 4
years, breast MRI identified primary breast tumors in 30 of 47 women
(64%) with stage II or III occult disease. Surgery or clinical
follow-up confirmed the absence of breast cancer in 15 patients.
There was one false-positive and one false-negative result.
Thus, MR breast imaging yielded a sensitivity of 97%, specificity of
73%, positive predictive value of 84%, and negative predictive value
of 95% when used in women with stage II/III occult primary breast
cancer, said Dr. Morris, associate attending radiologist, Memorial
Sloan-Kettering Cancer Center.
Breast MRI altered the surgical management of 21 of these patients
(45%), allowing 9 women (19%) to have lumpectomy rather than
mastectomy and 12 (26%) to have no surgery at all.
Even more women with stage II/III occult primary breast cancer may be
spared mastectomy on the basis of breast MRI, Dr. Morris said. She
explained that the majority of the women who had mastectomy
were early in our experience, and both the surgeons and the
radiologists were not confident enough in our results to recommend a
change from traditional therapy, which is mastectomy. Now, however,
if a patient has a negative MRI scan, we treat with radiotherapy only.
The majority of women undergoing lumpectomy in this study had tumors
that were undetectable by standard physical examination but could be
palpated by the surgeon during resection. Once we were able to
identify where the lesion was on MRI, the surgeons went back and
examined the patient, and they were able to palpate something they
felt comfortable about removing in the operating room, Dr.
Five patients who underwent mastectomy had multicentric disease. One
woman had a primary tumor with a spiculated mass and extensive ductal
carcinoma in situ (DCIS) throughout the remainder of the breast.
Another patient had metastatic involvement in the axillary lymph
nodes and several ill-defined masses that represented multifocal
invasive cancer as well as posterior enhancement that reflected DCIS.
Results in Stage IV Disease
Breast MRI was less successful in finding a primary tumor in women
with stage IV occult breast cancer; it identified a malignancy in
only 1 of 12 stage IV patients (8%). MRI was negative in 5 patients,
confirmed on follow-up. There were six false-positive findings. Thus,
MRI had a sensitivity of 100%, specificity of 45%, positive
predictive value of 14%, and negative predictive value of 100% for
detecting stage IV disease.
Because of the six false-positive findings, which necessitated
percutaneous core or aspiration biopsy, Dr. Morris concluded that
it is uncertain for stage IV patients whether MRI may be
valuable in this setting. We need to evaluate this with future
studies with larger numbers.
Breast MRI examinations in this study were done with a 1.5 T Signa GE
magnet using a dedicated breast coil. Fat-suppressed T1-weighted
images were acquired with a three-dimensional gradient-echo pulse
sequence before and after gadolinium-DTPA was administered at a rate
of 0.1 mmol/kg.