Rebound growth of hepatic colorectal metastases after neo-adjuvant chemotherapy: effect on survival after resection

Beyond CT: A Case Analysis of Serial [18F]FDG PET/CT for Assessment of Necrosis and Early Recurrence in Colorectal Liver Metastases

Colorectal cancer is a common malignancy, with the liver being the most frequent site of metastases. [18F] Fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) has emerged as a valuable tool in detecting and evaluating liver metastases and extrahepatic disease. Herein, we present a case of a 76-year-old male with colorectal cancer associated with lung and liver metastases. The patient received 12 chemoimmunotherapy cycles and was then put on maintenance cetuximab; serial [18F]FDG PET/CT scans were utilized to evaluate treatment response. The patient exhibited a positive response to chemoimmunotherapy, with regression of rectal disease and resolution of pulmonary metastatic nodules. Serial [18F]FDG PET/CT scans unveiled three distinct necrotic patterns. The case report advocates that [18F]FDG PET/CT plays an important role in evaluating colorectal liver metastases (CRLM) response to treatment, identifying transient necrosis, early recurrence, and emphasizing the limitations of post-treatment CT scans in identifying early CRLM recurrence. Integrating functional imaging, particularly [18F]FDG PET/CT, promises for management monitoring and surveillance of CRLM patients.

Oncologic aspects of the decision-making process for surgical approach for colorectal liver metastases progressing during chemotherapy

Colorectal cancer represents the third most diagnosed malignancy in the world. The liver is the main site of metastatic disease, affected in 30% of patients with newly diagnosed disease. Complete resection is considered the only potentially curative treatment for colorectal liver metastasis (CRLM), with a 5-year survival rate ranging from 35% to 58%. However, up to 80% of patients have initially unresectable disease, due to extrahepatic disease or bilobar multiple liver nodules. The availability of increasingly effective systemic chemotherapy has contributed to converting patients with initially unresectable liver metastases to resectable disease, improving long-term outcomes, and accessing tumor biology. In recent years, response to preoperative systemic chemotherapy before liver resection has been established as a major prognostic factor. Some studies have demonstrated that patients with regression of hepatic metastases while on chemotherapy have improved outcomes when compared to patients with stabilization or progression of the disease. Even if disease progression during chemotherapy represents an independent negative prognostic factor, some patients may still benefit from surgery, given the role of this modality as the main treatment with curative intent for patients with CRLM. In selected cases, based on size, the number of lesions, and tumor markers, surgery may be offered despite the less favorable prognosis and as an option for non-chemo responders.

Neoadjuvant Chemotherapy without Radiation in Colorectal Cancer

In colon cancer, primary surgery followed by postoperative chemotherapy represents the standard of care. In rectal cancer, the standard of care is preoperative radiotherapy or chemoradiation, which significantly reduces local recurrence but has no impact on subsequent metastatic disease or overall survival. The administration of neoadjuvant chemotherapy (NACT) before surgery can increase the chance of a curative resection and improves long-term outcomes in patients with liver metastases. Hence, NACT is being explored in both primary rectal and colon cancers as an alternative strategy to shrink the tumor, facilitate a curative resection, and simultaneously counter the risk of metastases. Yet, this lack of clarity regarding the precise aims of NACT (downstaging, maximizing response, or improving survival) is hindering progress. The appropriate cytotoxic agents, the optimal regimen, the number of cycles, or duration of NACT prior to surgery or in the postoperative setting remains undefined. Several potential strategies for integrating NACT are discussed with their advantages and disadvantages.

Colorectal liver metastases: radiopathological correlation

With the development of chemotherapy regimens, targeted therapies, and hepatic surgery, the survival of patients with colorectal liver metastases (CRLM) has dramatically improved. Imaging plays a central role for the diagnosis, staging, and treatment allocation in these patients. To interpret CRLM on imaging, radiologists must be familiar with the main imaging features of untreated tumors as well as the modifications induced by systemic therapies, and their meaning in relation to pathological tumor response and tumor biology. CRLM have the same histological features as the primary tumor. Most are “non-otherwise specified” (NOS) adenocarcinomas. The mucinous tumor is the most common of the rare subtypes. In NOS tumors, imaging usually differentiates central areas of necrosis from peripheral proliferating tumors and desmoplastic reaction. Areas of mucin mixed with fibrosis are seen in mucinous subtypes to help differentiate the metastases from other tumors cysts or hemangiomas. After treatment, the viable tumor is gradually replaced by ischemic-like necrosis and fibrosis, and remnants cells are mainly located on the periphery of tumors. Imaging can help predict the degree of tumor response, but changes can be difficult to differentiate from the pretherapeutic appearance. When chemotherapy is interrupted or in case of resistance to treatment, a peripheral infiltrating halo of tumor growth may appear. The purpose of the article is to illustrate the significance of the imaging features of colorectal liver metastases during systemic therapy, using radiopathological correlations.