Predictors Of A True Complete Response In Colorectal Liver Metastases That Disappear Radiographically Following Chemotherapy

4058 Background: During chemotherapy for colorectal liver metastases (LM), some lesions disappear by CT scan. This may represent a true complete response (CR) with eradication of tumor or a reduced sensitivity of imaging due to chemotherapy induced hepatic steatosis. This study aimed to determine the significance of radiologic disappearance of LM treated with chemotherapy and factors predictive of a true CR. Methods: Between 2000 and 2003, 435 patients evaluated by a hepatobiliary surgeon were treated with neoadjuvant chemotherapy for LM. Inclusion criteria were fewer than 12 LM initially, disappearance of one or more LM by CT scan and a clinical follow-up of at least 1 year after disappearance. A pathologic CR (pCR) was defined as the absence of a LM in the resected specimen, a durable clinical CR (cCR) was defined as a LM that did not reappear during follow-up imaging. A LM was defined as found if it was detected by other imaging (MRI), at resection, or if it recurred during follow-up. LM that were found were compared to pCR and durable cCR to determine factors predictive of a true CR. Results: During chemotherapy, 39 (9%) patients had a total of 117 LM disappear by follow-up CT scan. The outcome is shown in the Table . Treatment with hepatic arterial infusion (HAI) chemotherapy (n=22) was associated with a significantly higher rate of pCR or durable cCR (42% vs. 14%, p<0.001). LM were also significantly more likely to represent a pCR or durable cCR when the surrounding liver did not demonstrate steatosis (p<0.001), when the patient’s BMI was <30 kg/m2 (p=0.002), and when a preoperative MRI was performed (p=0.01). Conclusions: Among disappearing LM, a pCR occurs in 37% and a durable cCR in 26%, yielding a true CR rate of 63%. The disappearing LM in patients treated with HAI chemotherapy were more likely to a represent true CR when compared to systemic chemotherapy alone. Hepatic steatosis and obesity impaired the ability to detect lesions by CT scan and MRI improved the preoperative detection rate of disappearing LM. [Table: see text] No significant financial relationships to disclose.