VALUE OF 99m Tc-ARCITUMOMAB SPECT CO-REGISTERED TO X-RAY CT FOR SUSPECTED METASTATIC BREAST CARCINOMA

VALUE OF ^99mTc-ARCITUMOMAB SPECT CO-REGISTERED TO X-RAY CT FOR SUSPECTED METASTATIC BREAST CARCINOMA

Breast Cancer Research & Treatment 2001; 69: 237 – Poster 203

J. Rettig, Arlington Cancer Center Arlington, TX

_Background:_{Accurate disclosure of metastatic breast carcinoma
directly effects patient evaluation and selection of therapy. When CT results
are negative, reveal stable or equivocal findings despite rising serum CEA le}_vel_{s, further evaluation is
warranted. CEA expression has been reported in the vast majority of breast
carcinoma specimens although blood CEA le}_vel_{s seldom are elevated in
patients with localized primary disease.}

_Objective:_{To determine the utility of x-ray Computed Tomography
(CT) co-registered to nuclear medicine Single Photon Emission Tomography
(SPECT) to detect metastatic breast carcinoma.}

_Methods:_{The study group consisted of fourteen patients with primary breast
carcinoma staged no higher than T4bN2M0 who
subsequently de}_vel_{oped elevated serum CEA le}_vel_{s ranging from 6.5-820.0 ng/ml. Comparison CTs were
obtained at most one month prior to the co-registration procedure. Samples for
serum CEA assays were drawn 1-7 days prior to immunoscintigraphy. Prior to
imaging, hot/cold fiduciary markers were affixed to anatomic reference points
to facilitate co-registration. All patients were examined by CT and SPECT.
Patients proceeded directly from the gamma camera to the spiral CT unit to
ensure consistent placement of the markers. Whole body planar and SPECT images
of the pelvis and abdomen were acquired 3-4 hours post infusion of}^99m_{Tc-arcitumomab}_{(Immunomedics, Inc. Morris
Plains, NJ). If needed, SPECT images of the chest were obtained 6-24 hours post
infusion. Two patients had multiple immunoscintigrams
and did not de}_vel_{op human anti-mouse
antibodies (}_HAMA_{). The CTs
were evaluated on their own. Areas in question on the CT studies were
co-registered to the corresponding SPECT by alignment of the markers via a Voxel unit. The resultant co-registered study was reviewed
directly from the computer screen in all three orthogonal planes and with full
knowledge of all available clinical data.}

_Results:_{In positive CT studies with no interval change and elevated CEA le}_vel_{s, the co-registered images
identified 15 additional sites of metastatic involvement. Positive uptake was
found in all 7 lesions stable over 2 or more CTs. In
a subset of 4 patients with CT findings of insufficient magnitude to be read as
positive, the co-registered studies identified at least one additional lesion
in 2 patients.}

_Conclusion:_{Co-registration of CT/SPECT using}^99m_{Tc-arcitumomab}_{appears to be a valuable
tool for the detection of metastatic breast carcinoma.}