br proportional hazards regression models were used

proportional hazards regression models were used for the unadjusted univariate and adjusted multivariate survival analyses. Proportionality assumptions for the Cox regression models were tested, as well as Schoenfeld residuals plots for each subsite location over time. Variables and pairwise interactions included in the full Cox models are covariates that have been reported previously to have associations with CRC cancer mortality. For the prognostic significance of variables, the Cox regression was performed to obtain the unadjusted and adjusted ha-zards ratios (HRs) at 95% confidence intervals (CIs) in OS for RCC, LCC and ReC patients within each subgroup, controlling for all other vari-ables. Entry and removal probabilities for stepwise-regression were 0.05 and 0.10, respectively. In addition, Lakatos method was used to determine the power of the study. Most of statistical analyses were performed with SPSS software (SPSS Inc., Chicago, IL), using two-sided testing with a significance level at p-value of 0.05. SAS version 9.1.3 (SAS Institute), was used to determine the power of the study.
3. Results
3.1. Patients’ characteristics by epidemiological and clinicopathological features
With respect to the clinico-pathological features of the cases, the histologic grade was consistent across each subsite location, with only 4.4% of tumors being poorly differentiated. A greater proportion of cases had a higher level of tumor depth of invasion (T3-4 = 74.1%) with no regional 6-diazo-5-oxo-L-nor-Leucine node metastasis (N0 = 57.6%) and no distant metastasis (M0 = 88.9%). When stratified by tumor node metastasis stage, more than 55.4% of all cases were at stage I-II in each of the subsite locations of CRC. In TNM stage III-IV, patients with LCC (23.08%) were slightly frequently higher compared to RCC (20.58%), but no statistical significant (P = 0.693). In addition, patients with RCC exhibited a higher frequency of distant metastasis M1(36.67%) com-pared to only 28.33% and 35.0% for LCC and ReC respectively.
There were significant differences between subsite location re-garding smoking status, drinking status, tumor grade, T-stage, M-stage (all, P < 0.05). Concerning the treatment regimens, more than half of all cases did not have chemotherapy (55.4%) and they were either at stage I-II. In contrast, patients from stage III-IV received either FOLFOX or FOLFIRI.
3.2. Survival outcomes after CRC diagnosis
Median follow-up duration was 68.62 months (range, 0–112.70 months). Unadjusted Kaplan Meier survival curves based on subsite location revealed significantly better overall median survival (OS)
Table 1
Epidemiological and Clinicopathological Characteristics of post-surgical patients with colorectal cancer (CRC).
Characteristics CRC RCC LCC ReC P-value
Gender
Smoking
Drinking
Residence
Tumor Grade
T-Stage
N-Stage
M-Stage
TNM-Stage
Adjuvanta chemotherapy
Abbreviation: CRC-colorectal cancer, RCC-right colon cancer, LCC-left colon cancer, ReC-rectum cancer,:TNM-tumor-node-metastasis, FOLFOX-Folinic acid
Fluorouracil Oxaliplatin, FOLFIRI-Folinic acid Fluorouracil Irinotecan. a: Only patients with TNM III/IV have received a chemotherapy regimen.
S. Abasse Kassim, et al.
Table 2
Univariate and Multivariate analysis of the risk of mortality among colorectal cancer subsite location by epidemiological and clinico-pathological characteristics.
Unadjusted
Adjusted
Unadjusted
Adjusted
Unadjusted
Adjusted
Abbreviation: CRC-colorectal cancer, RCC-right colon cancer, LCC-left colon cancer, ReC-rectum cancer, TNM-tumor-node-metastasis, FOLFOX-Folinic acid Fluorouracil Oxaliplatin, FOLFIRI-Folinic acid Fluorouracil Irinotecan, OS-Overall survival, HR-Hazard ratio, 95%CI-95%confidence interval.