10 Gastric Cancer
Hossein Jadvar and Shahram Bouyadlou
History
64-year-old male with a history of gastric cancer, status post partial gastrectomy, with subsequent radiotherapy and chemotherapy one year ago. A recent CT demonstrated a suspicious area in the medial segment of the left lobe of the liver. This study is per- formed to evaluate for evidence of metastatic disease.
Findings
The pulmonary exam is negative by 18-FDG PET scintigraphy. Scattered atelectasis is evident on CT as well as a left-lung base cystic area in the lung. No pulmonary nodule is apparent. The mediastinum is negative. The abdomen is remarkable for a liver dome lesion which is intensely hypermetabolic (Figure 10.1.1) with central hypoactivity con- sistent with central necrosis (Figure 10.1.2). This is somewhat ill-defined on the non- contrast CT but it is measured at about 3.3 cm in diameter. No other hepatic lesion is apparent. Multiple upper abdominal surgical clips are consistent with the history.
There is moderate calcification in the normal caliber abdominal aorta. There is promi- nent but presumed physiologic diffuse bowel activity. In the pelvis, the urinary bladder appears more distended than usually seen on a post-voiding exam. This may reflect prostate enlargement.
Impression
1. Solitary liver dome metastasis of approximately 3.3 cm diameter with central necro- sis. There is no other evidence for metastatic disease by PET scintigraphy with CT attenuation correction.
2. Increased postvoiding residual in the urinary bladder; prior partial gastrectomy with multiple upper abdominal surgical clips; scattered pulmonary atelectasis and left lung base cyst.
Pearls and Pitfalls
• PET may be useful in the evaluation of recurrent gastric cancer and localize the disease where CT is nondiagnostic.1,2
• PET can alter the clinical management of patients with recurrent gastric cancer.1,2,3
Case 10.1
115
• In a retrospective study, PET demonstrates a sensitivity of 62% and specificity of 60%
for a group of primary tumors with signet cell differentiation.1,2,3
• The positive predictive value of PET in gastric cancer is 78% as opposed to a nega- tive predictive value of 60%.1,2,3
• Due to the poor sensitivity and negative predictive value, most authorities agree PET imaging is not a useful screening tool for gastric cancer.1,2,3
FIGURE10.1.1.
FIGURE10.1.2.
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Discussion
Gastric cancer ranked fourteenth among major malignancies in the US and remains the least studied malignancy with F-18 FDG PET imaging. Studies suggest that expo- sure to an etiologic agent at an early age (H. pylori infection, cigarette smoking, and low levels of dietary vitamin C) may be responsible for gastric cancer that eventually leads to up-regulation of expression of cox-2 enzyme.
Early satiety and abdominal tenderness are some of early-stage nonspecific signs for stomach cancer. Weight loss or palpable mass is late in the course of the disease.
Endoscopy, gastric cytology washing, and barium x-ray are commonly used for diag- nosis. Resection is the cornerstone for cure. Chemotherapy may be used for palliative treatment. Prognosis is good only if the malignancy is limited to the mucosa and submucosa.
History
63-year-old male who has a history of gastric cancer diagnosed status post chemother- apy two years ago. His most recent CT revealed a suspicious lesion in the medial aspect of the inferior portion of the liver. The patient is being evaluated for metastatic disease.
Findings
In the abdomen, there are several small hepatic metastases (Figures 10.2.1 and 10.2.2).
There is a large subhepatic (Figure 10.2.3) and several other large peritoneal implants (Figures 10.2.4 and 10.2.5). The low left pelvic focus is probably a peritoneal implant in the rectovesical recess (Figure 10.2.6). The chest is clear.
Impression
Multiple lesions found in the liver and the abdomen consistent with disseminated implants from known gastric cancer.
Case 10.2
FIGURE10.2.1.
FIGURE10.2.4. FIGURE10.2.5.
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Pearls and Pitfalls
• PET-negative patients have a higher survival rate than PET-positive patients, 18.5 months vs. 6.9 months, respectively.1,3
Discussion
PET scintigraphy is useful for imaging in advanced, metastatic, or recurrent disease, although there is no direct correlation between uptake and histopathological appear- ance. F-18 FDG is an important tool in staging, treatment planning, and in assessing response to therapy.
Change in Treatment
There is a definite pre- and post-PET management change in this patient. The patient initially refuses chemotherapy due to its side effect profile and would prefer radio- therapy instead. After the PET findings, the patient was convinced that chemotherapy would be the best therapeutic approach to his therapy planning.
FIGURE10.2.6.
