Case Report PET in Rectal Carcinoma Josefina Jofré M 1, Paulina Sierralta C 1, José Canessa G 1,2, Pamela Humeres A 3, Gabriel Castro M 4, Teresa Massardo V 1,4 1 Centro PET de Imágenes Moleculares, Hospital Militar de Santiago, Chile. 2 Hospital DIPRECA, Santiago, Chile. 3 Clínica Santa María, Santiago, Chile. 4 Hospital Clínico Universidad de Chile, Santiago, Chile.
Clinical History Seventy-four year old man with history of rectal carcinoma. Receives neoadjuvant chemo-radiotherapy (QT/RT) before surgery. CT examination of abdomen and pelvis showed a mass with exofitic component in left postero-lateral aspect of rectum and a small adjacent lymph node (1 cm).
Clinical History Chest-Rx showed increased left pleural effusion and basal atelectasia already observed a year before. The patient is operated the following month, being with ileosthomy thereafter. Pathology showed rectal ulcerative lesion 7x8x3 cm corresponding to a carcinoma of tubular type with mucinous focal component, lymphatic invasion, infiltrative margin and no evidence of blood vessel invasion, with 2/3 positive lymph nodes. Conclusion: colon Ca - Dukes C Group C2 (Astler & Coller), Group III (Jass).
Clinical History A PET-FDG study is performed as parto of post-surgical work-up, which showed hypermetabolic focii on the basal aspect of left lung and in right lobe of the liver, suggesting metastatic disease (Figure 1). Additionally, there is a finding at the infero-vesical region which could correspond to local recurrence or, more likely, to post-surgical inflammatory changes.
Figure 1.- Post-operative PET-FDG (coronal, central sagittal and 3D reconstruction). There is an active area in left lung and a second one with central hypoactivity in right hepatic lobe (red arrows).
Clinical History New series of chemotherapy is applied, together with surgical removal of lung and hepatic masses. Pathology shows metastatic tubular adenocarcinoma. CEA levels are normal during the following year, after which an elevation is observed. Re-staging workup is decided accordingly. A chest-rx is normal. Abdominal CT: post-surgical changes in right hepatic lobe. A new PET study shows an area of FDG uptake in left lung which was not present in the initial study (Figure 2). Previous lesions disappeared.
Figure 2.- PET-FDG scan for re-staging. Hypermetabolic area in left hemithorax is apparent. Lesions seen on previous study have disappeared.
Clinical History Conventional CT of the chest only shows residual changes in left base which is not suspicious of cancer. Because of discrepancy with PET results, a multi-slice CT is requested, which is positive for possible neoplastic lesion involving left hilium and bronchial branches (Figure 3).
Figure 3.- Multi-slice CT showing hiliar mass with bronchial involvement.
Discussion Because of the imaging presentation, diagnostic dilemma is to differentiate between primary bronchogenic carcinoma (for which surgery would eventually be indicated) and metastasis from rectal carcinoma. Since there were no other findings in the PET study that could explain CEA elevation, the finding was interpreted as metastatic and chemo-radiotherapy was performed (unfortunately, no biopsy of the pulmonary lesion was carried out). Follow-up information is lacking but the patient died 3 years later.
Conclusion
Teaching points PET-FDG can be used for initial staging and restaging in rectal carcinoma. PET-FDG can help clarify the origin of new CT findings.
Bibliography Janssen MH, Ollers MC, van Stiphout RG, Buijsen J, van den Bogaard J, de Ruysscher, et al. Evaluation of early metabolic responses in rectal cancer during combined radiochemotherapy or radiotherapy alone: sequential FDG-PET-CT findings. Radiother Oncol 2010;94:151-5. Xu H, Zhang M, Zhai G, Li B. The clinical significance of 18F-FDG-PET/CT in early detection of second primary malignancy in cancer patients. J Cancer Res Clin Oncol 2010;136:1125-34. Kau T, Reinprecht P, Eicher W, Lind P, Starlinger M, Hausegger KA. FDG PET/CT in the detection of recurrent rectal cancer. Int Surg 2009;94:315-24. Davey K, Heriot AG, Mackay J, Drummond E, Hogg A, Ngan S, et al. The impact of 18- fluorodeoxyglucose positron emission tomography-computed tomography on the staging and management of primary rectal cancer. Dis Colon Rectum 2008;51:997-1003.