False Liver Metastasis by Positron Emission Tomography/Computed Tomography Scan after Chemoradiotherapy for Esophageal Cancer-Potential Overstaged Pitfalls of Treatment

Abstract

In patients with esophageal cancer undergoing neoadjuvant chemoradiotherapy (nCRT), subsequent restaging with F-18-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) can reveal the presence of interval metastases, such as liver metastases, in approximately 10% of cases. Nevertheless, it is not uncommon in clinical practice to observe focal FDG uptake in the liver that is not associated with liver metastases but rather with radiation-induced liver injury (RILI), which can result in the overstaging of the disease. Liver radiation damage is also a concern during distal esophageal cancer radiotherapy due to its proximity to the left liver lobe, typically included in the radiation field. Post-CRT, if FDG activity appears in the left or caudate liver lobes, a thorough investigation is needed to confirm or rule out distant metastases. The increased FDG uptake in liver lobes post-CRT often presents a diagnostic dilemma. Distinguishing between radiation-induced liver disease and metastasis is vital for appropriate patient management, necessitating a combination of imaging techniques and an understanding of the factors influencing the radiation response. Diagnosis involves identifying new foci of hepatic FDG avidity on PET/CT scans. Geographic regions of hypoattenuation on CT and well-demarcated regions with specific enhancement patterns on contrast-enhanced CT scans and MRI are characteristic of radiation-induced liver disease (RILD). Lack of mass effect on all three modalities (CT, MRI, PET) indicates RILD. Resolution of abnormalities on subsequent examinations also helps in diagnosing RILD. Moreover, it can also help to rule out occult metastases, thereby excluding those patients from further surgery who will not benefit from esophagectomy with curative intent.

Keywords: F-18-fluorodeoxyglucose (18F-FDG); false liver metastasis; neoadjuvant chemoradiotherapy (nCRT); positron emission tomography–computed tomography (PET-CT); radiation-induced liver disease (RILD); radiation-induced liver injury (RILI).

Figure 1

Schematic figure of the current gold standard procedure for esophageal cancer treatment with nCRT for about 4 weeks followed by non-avid FDG PET-CT proceeding esophagectomy.

Figure 2

(A) Sonography of the liver reveals a hypoechoic appearance over the caudate lobe. (B) The contrast CT scan shows decreased enhancement in S1 of the liver. (C) MRI T1-weighted pictures of the liver reveal a low signal intensity over the caudate lobe. (D) MRI T2-weighted pictures of the liver indicate a strong signal intensity over the caudate lobe. Reprinted with permission from Sen-Ei Shai et al. (2020) [48].

Figure 3

Prior to neoadjuvant chemoradiotherapy (nCRT), the esophageal tumor exhibited high FDG uptake (9.7 × 5.6 cm, SUVmax: 29.3/h) (red circles). There were no active lesions in liver segment I before nCRT (red arrows). Reprinted with permission from Sen-Ei Shai et al. (2020) [48].

Figure 4

Shows esophageal tumor reduction after six weeks of nCRT (2.1 × 1.6 cm, SUVmax: 7.7/h, highlighted by yellow circles). Reprinted with permission from Sen-Ei Shai et al. (2020) [48].

Figure 5

Six weeks following nCRT, a new FDG-avid lesion was found in liver segment I (3.5 × 1.5 cm, SUVmax: 4.2/h, indicated by yellow arrows). Reprinted with permission from Sen-Ei Shai et al. (2020) [48].

Figure 6

(A) The normal liver versus the inflamed caudate lobe. (B) An up-close image of the liver, showing dark red, soft tissue, and blood infiltration in the caudate lobe. Pathology of the liver caudate lobe. (C) A low-power field reveals no tumor metastasis at a magnification of 20×. (D) A high power field indicates congestion with attenuated hepatic cords filled with erythrocytes at a magnification of 40×. Reprinted with permission from Sen-Ei Shai et al. (2020) [48].