Date Published: December 28, 2018
Publisher: Impact Journals
Author(s): Lin Yang, Xingli Yang, Wenzhuo He, Shousheng Liu, Chang Jiang, Kunqian Xie, Kunwei Peng, Yafei You, Bei Zhang, Liangping Xia.
Population-based evaluations of the incidence of metastatic colorectal cancer at diagnosis among different age groups are lacking. Therefore, we investigated the effects of age at diagnosis on metastatic colorectal cancer and patients’ prognoses. The Surveillance, Epidemiology, and End Results database was used to identify patients diagnosed with metastatic colorectal cancer. Multivariate Cox regression analyses were performed to identify factors associated with poor survival. The Kaplan–Meier analysis was used to estimate survival differences between the subgroups. We identified 30,333 adult patients diagnosed with metastatic colorectal cancer between 2010 and 2014. The younger and middle-aged groups had better survival than the older group when brain metastasis was not involved. The liver was the most common site of metastasis followed by the liver and lung combined. Age at diagnosis was an independent factor in patients’ survival. Survival differences between two and three-sites of metastases were found in the middle-aged and older groups but not in the younger group. No survival differences between three and four sites of metastases were found in any of the age groups. Therefore, the incidence and prognosis of metastatic sites for metastatic colorectal cancer varied by age group.
Despite the improved survival of colorectal cancer (CRC) patients, metastatic disease still accounts for a high number of cancer-related deaths. Approximately 20% of patients present with metastatic disease at the time diagnosis . The most common sites of CRC metastasis are the liver, lungs, and peritoneum, but there are other sites of metastasis, such as the bones, brain, and distant lymph nodes [2-5]. Autopsy studies have examined metastatic patterns and found that different primary cancers metastasize with different frequencies to different sites  and studies of CRC have revealed that histological subtypes influence metastatic patterns .
This large-scale study provided more in-depth knowledge and a better understanding of the heterogeneity of colorectal cancer among different age groups. We found that a younger age at diagnosis was associated with being White, having advanced N stage, more lymph node involvement, and a tendency to have LCC. Patients in the younger age group were more likely to have single liver metastasis, but less likely to have single lung metastasis compared with patients in the older age group, and the younger patients had better survival when brain metastasis was not involved.
Our research summarized the tumor characteristics and survival outcomes of patients in three age groups with mCRC from a large sample of the population. Age was a robust prognostic factor and patients in the younger age group were more likely to have single liver metastasis, but less likely to have single lung metastasis compared with the patients in the older age group. The younger patients had better survival when their cancer did not involve brain metastasis. To determine more appropriate healthcare for aging patients with mCRC, further investigations of biochemical and molecular changes with aging are required.
Data were retrieved from the SEER database between 2010 and 2014. The datasets, which are available in the SEER dataset repository at: https://seer.cancer.gov/, represented 30% of the United States population. Pathology was classified as adenocarcinoma (AC), mucinous adenocarcinoma (MC), or other. Grade was defined as well differentiated, moderately differentiated, and poorly differentiated, or undifferentiated. Tumor location and their anatomical components, including RCC were classified as follows: RCC (cecum, ascending colon, hepatic flexure, and transverse colon), LCC (splenic flexure, descending colon, and sigmoid colon), RSC (recto-sigmoid junction and rectum), and appendix cancer . Race/ethnicity was categorized as previously described . The SEER 18 dataset categorized ethnicity as White, African-American, Native American/Alaskan Native, Asian/Pacific Islander, and unknown. The presence of bone, lung, liver, and brain metastases at diagnosis were available in the SEER database and were categorized as the number of metastases among the patients in our study. Patients were observed after the first diagnosis of CRC until the last follow-up, death, or end of the study, whichever occurred first.