Prognostic factors and individualized nomograms predicting overall survival in stage IV rectal cancer patients with different metastatic status: a SEER-based study.

Background: The prognosis of rectal cancer patients with different metastatic status was significantly different. Our aim was to identify prognostic factors for metastatic rectal cancer (mRC) patients with different metastatic status and to construct specific nomograms to predict overall survival (OS).

Methods: This study retrospectively analyzed mRC patients from 2010 to 2016 in the Surveillance, Epidemiology, and End Results Program database. All patients were ultimately divided into four groups: synchronous liver metastasis, synchronous lung metastasis, synchronous other organs metastasis and synchronous multiple metastases. Univariate and multivariate cox analyses were performed to screen out independent factors for each group. Individualized nomograms were constructed in different metastatic modes. The concordance index (C-index), decision curve analysis (DCA), time-dependent receiver operating characteristic (ROC) curve and calibration curve were performed to verify these nomograms.

Results: Finally, 10,407 mRC patients were included in this study. Age, tumor grade, surgery of primary tumor, and chemotherapy were identified as common independent prognostic factors for each subgroup (all P<0.05). Other independent prognostic factors specific to each group included radiotherapy and marital status in the liver metastasis group, race, N stage, and the presence or absence of site-specific metastases in the multiple metastases group (all P<0.05). Higher T staging suggested worse OS in the group with liver, lung, and multiple site metastases. Individualized nomograms predicting 1-, 2-, and 3-year OS for each group were constructed by combining all independently significant risk factors in each group. The area under the curve (AUC) values and C-indexes of these nomograms created by each subgroup were greater than 0.7. All calibration curves and DCA curves showed that these nomograms had good clinical application significance.

Conclusions: Individualized prognostic nomograms were constructed for mRC patients with different metastatic status based on different prognostic factors. These nomograms presented satisfactory predictive effects, which helps to provide survival assessment and individualized treatment decision-making for mRC patients with different metastatic status.