The 70-year-old patient had initially presented with rectal bleeding.
Colonoscopy revealed a large ulcerated, fungating, friable mass at 30 cm in the
sigmoid colon. Biopsy showed an invasive adenocarcinoma. The imaging studies
were negative for metastatic disease. Therefore, the patient subsequently
underwent a sigmoid colon resection.
Pathology was consistent with moderately differentiated adenocarcinoma
arising from a tubular adenoma with mucinous features; three out of eight lymph
nodes were involved. Unfortunately, the surgical margins were positive. He went
on to receive adjuvant chemotherapy with a modified FOLFOX6 regimen that was
complicated by moderate neuropathy. Since then he has been monitored closely
About two years later, the surveillance CT scan showed an enlarging soft
tissue mass in the anterior mid-pelvis measuring 2.6 cm and a 3 cm intraluminal
mass at the site of anastomosis.
Axial PET/CT image demonstrates hypermetabolic activity corresponding to the
recurrent carcinoma in the left sigmoid colon. Upper left image is axial CT
scan, upper right image is corresponding PET image, lower left image is fusion
image containing PET images displayed on a color scale and CT images displayed
on a gray scale. Lower right image is maximum intensity project image of whole
body PET study.
Photos by M Ghesani
The PET/CT study also showed a hypermetabolic omental mass consistent
with peritoneal carcinomatosis, a hypermetabolic focus in the area of
anastomosis, and an additional hypermetabolic focus in the descending colon
without anatomic correlate. The subsequent biopsy confirmed recurrence at the
site of anastomosis.
Due to the patients underlying comorbidities, he was believed to
be a poor candidate for hyperthermic therapy or clinical trial. As such, he
received palliative systemic chemotherapy with the FOLFIRI regimen without
bevacizumab (Avastin, Genentech), in light of prior history of stroke,
peripheral vascular disease and coronary artery disease. He received six
cycles, but his last cycle was complicated by viral gastroenteritis resulting
in prolonged hospitalization. Thereafter, the patient elected to cancel his
therapy and to have expectant management.
Axial PET/CT image craniad to the Figure 1 demonstrates hypermetabolic activity
associated with metastatic omental implant. Display convention is the same as
Of note, the restaging follow-up PET/CT after FOLFIRI regimen showed
some tumor shrinkage, with reduction in the metabolic activity of the lesions.
A six-month interval follow-up PET/CT again revealed progressive disease
corroborated by increasing carcinoembryonic antigen, but the patient largely
remained asymptomatic and continued to prefer expectant management.
Axial PET/CT image through the liver demonstrates a hypermetabolic focus in the
right lobe of the liver, suspicious for metastatic disease. Corresponding CT
image without the benefit of intravenous contrast demonstrates no focal lesion
in this patient with diffuse fatty infiltration of the liver.
He made the same decision after the repeat imaging six months later when
imaging again revealed further progressive disease.
This time the PET/CT revealed progression on the liver in the settings
of fatty liver infiltration, as well as worsening peritoneal carcinomatosis.
PET imaging has significantly changed the work up of a patient with the
colorectal cancer, particularly in the setting of recurrence, as well as both
hepatic and extrahepatic metastatic disease. Several studies have confirmed
that the fusion images of PET and CT improve accuracy, lesion characterization
Francis et al referred to the retrospective study of 45 patients with
colon cancer comparing PET/CT with PET alone; there was a decrease in the
number of equivocal readings by 50% for PET/CT. In addition, lesion
characterization increased by 30% and accurate localization by 25%. Overall
staging accuracy improved from 78% to 89% on a patient-by-patient analysis. In
another study of 65 patients with suspected or known colorectal carcinoma,
sensitivity and specificity for PET/CT was 96% and 97% compared to 77% and 89%
for PET alone. Similarly the sensitivity and specificity for metastases
detection were 95% and 98% for PET/CT compared to 66% and 79% for PET alone.
Figure 4: Axial PET/CT image through the liver demonstrates
another lesion in the left lobe of the liver.
Khan et al studied 23 patients with clinically suspected liver
metastases or presence of extrahepatic disease. Patients had a median age of
59, and all underwent fusion PET/CT. Seven patients (30%) were found to have
unexpected metastatic disease, not seen on CT findings in the colorectal
metastases group, including patients with hepatic metastases. Three patients
had hepatic metastases only, and eight patients had distant disease. Overall,
the treatment plan and clinical decision-making were changed in 21 of the 23
The PET/CT has proved to be useful, especially when conventional CT
fails to demonstrate recurrence. Votrubova et al retrospectively compared 84
patients with suspected recurrence. PET/CT correctly detected 40 out of 45
patents with colorectal cancer recurrence, proving that PET/CT is a valuable
study to distinguish viable tumor from reactive changes, thereby avoiding
Kosugi and colleagues prospectively evaluated PET/CT for staging of
lymph nodes and concluded that although PET/CT is markedly more sensitive than
CT for detection of N4 lymph node involvement, the number of metastatic lymph
nodes is difficult to determine.
Metastatic lesions to the liver from FDG-avid primary malignancies such
as colon carcinoma may be readily apparent on PET imaging. It should be noted
that these lesions may not be readily apparent on CT imaging of the liver,
unless the CT study is optimized with multiphase contrast enhanced acquisition.
Presence of diffuse liver disease such as fatty infiltration further
compromises ability of CT imaging to detect such lesions.
Liana Makarian, MD is an Oncology Fellow at St Lukes-Roosevelt
Munir Ghesani, MD, is Associate Clinical Professor of Radiology at
Columbia University College of Physicians and Surgeons and Attending
Radiologist at St.Lukes-Roosevelt Medical Center.
For more information:
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- Cohade C. J Nucl Med. 2003;44:1797-1803
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- Francis IR. Cancer Imaging. 2005;5
- Khan. European Journal of Surgical Oncology.
- Kosugi. Hepatogastroenterology. 2008; 5:398-402
- Shiepers C. J Nucl Med. 2003;44:1804-1805.
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