Influence of the Primary Tumor Location on the Pattern of Synchronous Metastatic Spread in Patients with Stage IV Colorectal Carcinoma, According to the 8 th Edition of the AJCC Staging System
Background and Aims: The correlations between primary tumor location (right colon cancer – RCC, left colon cancer – LCC and rectal cancer – RC) and the incidence of metastatic sites are scarce and divergent. The current study is the first which compares the pattern of metastatic distribution (M1a: metastasis to one organ/site, excluding peritoneum; M1b: two or more metastatic sites; M1c: peritoneal metastases) between RCC, LCC and RC, respectively.
Methods: All patients operated for colorectal cancer (CRC) between January 2006 and December 2015 were analyzed to assess the primary tumor location, the presence and site of synchronous metastases. Univariate analysis determined the statistical significance of association between each CRC location and the metastatic pattern. Multinomial logistical regression model compared the prevalence of each metastatic pattern for each CRC location.
Results: Out of 5,107 patients, 1,318 (25.80%) had metastases on the moment of CRC diagnosis. There were no statistically significant association between the metastatic pattern and the patients’ gender (M1a, p=0.321; M1b, p=0.539; M1c, p=0.417, Chi-square) or patients’ age (p=0.616 Mann–Whitney U-test). RC had a significant higher relative risk for M1a (RR of 1.437, p=0.014) and a lower relative risk for M1c (RR of 0.564, p=0.001), compared to LCC. On the contrary, compared with LCC, the RCC showed a significant lower relative risk for M1a (RR of 0.673, p=0.006) and a higher relative risk for M1c (RR of 1.834, p=0.0001).
Conclusion. There is a strong correlation between the primary location of CRC and the pattern of the metastatic spread, with potential prognostic implications.