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Background Clinically, metastatic rectal cancer has been considered a subset of left-sided colon cancer. However, heterogeneity has been proposed to exist between high and middle/low rectal cancers. We aimed to examine the efficacy of anti-epidermal growth factor receptor (EGFR) treatment for middle/low rectal and left-sided colon cancers. Methods This study enrolled 609 patients with metastatic colorectal cancer who were treated with anti-EGFR therapy. They were divided into groups based on primary tumour locations: the right-sided colon, the left-sided colon or the middle/low rectum. The efficacy of first-line and non-first-line anti-EGFR treatment was analysed. Genomic differences in colorectal cancer data from The Cancer Genome Atlas (TCGA) were investigated and visualised with OncoPrint and a clustered heatmap. Results On first-line anti-EGFR treatment, patients with middle/low rectal tumours had significantly lower progression-free survival, overall survival, and overall response rates (6.8 months, 27.8 months and 43%, respectively) than those with left-sided colon cancer (10.1 months, 38.3 months and 66%, respectively). Similar outcomes were also identified on non-first-line anti-EGFR treatment. In TCGA analysis, rectal tumours displayed genetic heterogeneity and shared features with both left- and right-sided colon cancer. Conclusions Anti-EGFR treatment has lower efficacy in metastatic middle/low rectal cancer than in left-sided colon cancer.

BACKGROUND: A significant proportion of patients with rectal cancer will present with synchronous metastasis at the time of diagnosis. Rates of OS for these patients are highly variable and previous attempts to build predictive models often have low predictive power, with concordance indexes (c-index) less than 0.70. METHODS: Using the National Cancer Database (2010–2014), we identified patients with synchronous metastatic rectal cancer. The data was split into a training dataset (diagnosis years 2010–2012), which was used to build the machine-learning model, and a testing dataset (diagnosis years 2013–2014), which was used to externally validate the model. A nomogram predicting 3-year overall survival was created using Cox proportional hazard regression with lasso-penalization. Predictors were selected based on clinical significance and availability in NCDB. Performance of the machine-learning model was assessed by c-index. RESULTS: A total of 4,098 and 3,107 patients were used to construct and validate the nomogram, respectively. Internally validated c-indexes at 1, 2, and 3 years were 0.816 (95% CI 0.813 – 0.818), 0.789 (95% CI 0.786 – 0.790), and 0.778 (95% CI 0.775 – 0.780), respectively. External validated c-indexes at 1, 2, and 3 years were 0.811, 0.779, and 0.778, respectively. CONCLUSIONS: There is wide variability in the OS for patients with metastatic rectal cancer, making accurate predictions difficult. However, using machine learning techniques, more accurate models can be built. This will aid patients and clinicians in setting expectations and making clinical decisions in this group of challenging patients.

To compare the cost-performance between planned short-course radiation and upfront concurrent chemoradiation on metastatic rectal cancer. A total of 75 patients with metastatic rectal cancer who underwent planned short-course radiation or upfront concurrent chemoradiation were enrolled. The Kaplan-Meier method was used to compute the survival rates. The χ2 test was used to compare baseline characteristics. The Cox proportional hazards model was applied to determine the prognostic influence of clinicopathological factors. The planned short-course radiation is superior to upfront concurrent chemoradiation in overall survival for the patients with metastatic rectal cancer (34.8 vs. 20.2 months, P = 0.010). The planned short-course radiation was an independent prognostic factor (P = 0.009, HR (95% CI) = 0.319(0.135–0.752)). The efficacy of radiation on downstaging was similar between planned short-course radiation and upfront concurrent chemoradiation. The total cost of concurrent chemoradiation is 4.52-fold more expensive than that of short-course radiation (340,142 vs. 75,106 NT dollars, respectively). Based on the impressive cost-performance of planned short-course radiation compared with upfront concurrent chemoradiation (better OS, modest downstaging and lower cost), planned short-course radiation should be the preferred radiation approach for managing metastatic rectal cancer.

We now describe the first example of a patient who developed perirenal hematoma during the course of bevacizumab-containing chemotherapy. A 59-years-old woman with metastatic rectal cancer treated with bevacizumab, who developed low back pain after 11 cycles of chemotherapy. CT-scan was consistent with perirenal hematoma and discontinuation of bevacizumab resulted in symptomatic improvement. Nontraumatic perirenal hematoma is a rare condition that can cause shock in severe cases. Given that several types of bleeding complication are known to be associated with bevacizumab treatment, we concluded that bevacizumab likely contributed to the perirenal hematoma in this case. Although the appropriate modification of bevacizumab treatment in the setting of perirenal hematoma is still unclear, physicians should be aware of this potential bevacizumab-associated bleeding complication.