Influence of histologic subtype on metastatic pattern in colorectal cancer.

Abstract

395 Background: In colorectal cancer (CRC) mucinous adenocarcinoma (MC) and signet-ring cell carcinoma (SRCC) have been associated with differences in metastatic patterns compared to the more common adenocarcinoma (AC). This study systematically evaluates metastatic patterns of different histological subtypes and analyses metastatic disease based upon primary tumor localization. Methods: A nationwide retrospective review of pathological records of 5,813 patients diagnosed with CRC who underwent an autopsy between 1991 and 2010 was performed. Patients were selected from the Dutch Pathology Registry (PALGA). To validate metastatic patterns in rectal cancer patients, data was compared to the prospective randomized multicentre TME-trial that investigated efficacy of preoperative radiotherapy. Results: In the autopsy study 1,675 patients with CRC had metastatic disease. Metastatic disease was more frequently found in MC and SRCC than in AC (33.9%, 61.2% and 27.5%; P< 0.0001) and more often had metastases at multiple sites (58.6% and 70.7% versus 49.9%; P=0.001). AC more commonly metastasized to the liver compared with MC and SRCC, 73.0% versus 52.2% and 31.7% (P<0.0001). The occurrence of metastases exclusively to the liver was less common in MC and SRCC patients. In SRCC patients, liver metastases were almost always observed in combination with other metastases. MC and SRCC metastasized to the peritoneal surface frequently, 48.2% and 51.2%, compared with 20.1% in AC (P<0.0001). Colon cancer patients presented more frequently with intra-abdominal metastases, than rectal cancer patients. Rectal cancer patients presented more often with extra-abdominal metastases. Results from the TME-trial confirmed findings in rectal cancer patients from the autopsy study. Conclusions: There are profound differences in metastatic patterns between different histological subtypes and the localization of the primary tumor in CRC. Findings from this study should encourage to take histological subtype into account during pre-operative examination for metastases and during follow-up. Results also indicate that these factors should be considered a stratification factor in future research initiatives focusing on advanced disease.