• Second Primary Cancer Occurrence after Colorectal Cancer: A Systematic Review and Meta-Analysis
  • Mohammad Zahedi,1,* Mohammad Yousefi,2 Amirreza Nasirzadeh,3 Parham Mortazavi,4 Reza Alizadeh-Navaei,5 Keyvan Heydari,6
    1. 1. Department of Medical Biotechnology, School of Allied Medicine, Iran University of Medical Sciences, Tehran, Iran 2. Student Research Committee, Iran University of Medical Sciences, Tehran, Iran
    2. Department of medicine, Faculty of Medicine, Semnan University of Medical Sciences, Semnan, Iran
    3. Student of Medical-Surgical Nursing, Student Research Committee, Mashhad University of Medical Sciences, Mashhad, Iran.
    4. 6. School of pharmacy, Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran.
    5. 9. Gastrointestinal Cancer Research Center, Mazandaran University of Medical Sciences, Iran.
    6. 8. Student Research Committee, School of Medicine, Mazandaran University of Medical Sciences, Iran.


  • Introduction: Introduction: Colorectal cancer (CRC) is the third most frequent cancer diagnosis and the second leading cause of cancer-related death. There is evidence of an increased risk of developing a second primary colorectal cancer in CRC patients. This systematic review and meta-analysis aims to provide a pooled relative risk of second primary cancer after colorectal cancer (SPCAC) in CRC patients based on available evidence.
  • Methods: Search Method: Medline (via PubMed), Web of Science, and Scopus databases were searched for English cohort studies that reported standard incidence ratio (SIR) of SPCAC up to 10 Aug 2020. This study was performed based on the PRISMA guideline. Heterogeneity across included studies was determined using the I2 statistic. We used the random‑effect models for pooled Standard Incidence Ratio (SIR) and 95% confidence intervals (CIs). Studies included if they met the following criteria: original studies with cohort design in the English language; studies that investigated and reported the SIR of second primary cancer after colorectal, colon, and rectum cancer. The pooled SIR of SPCAC based on the primary site of cancer was measured. Statistical analysis was performed using STATA version 11.0 (Stata Corp., College Station, TX)
  • Results: Results: A total of 6676 citations were identified through electronic database searches. After excluding 3507 duplicated papers, 3169 records were included after the screening. Through 30 extracted papers, 142429 confirmed SPCAC adult patients (more than 19 years old) were included in this meta-analysis. The SIR of SPCAC was 1.27 (95% CI 1.16-1.37) and was reported by 12 studies. The SIR of SPCAC for digestive, reproductive, and urinary organ’s involvement was 1.31 (95% CI 0.89-1.72), 1.45 (95% CI 0.99-1.90), and 1.27 (95% CI 1.10-1.45), respectively. In comparison to general populations, small intestine, endometrial, colon, and ovary cancer are most common in individuals with previous CRC and will surge in Colorectal cancer survivors (CCSs). Findings of this meta-analysis indicated that people with a history of CRCs are three times more likely prone to subsequent uterus and endometrial cancers (SIR: 3.03).
  • Conclusion: Conclusions: CCSs are more vulnerable to SPCAC of the small intestine and endometrium. The result of this study might be helpful for both clinicians and policymakers. Further investigations on etiologic factors for prevention and early diagnosis of SPCAC are suggested. Unavailable confounding characteristics such as smoking, alcohol intake, physical activity, food, and lifestyle, may restrict the findings.
  • Keywords: Secondary Cancer, Incidence, standard incidence ratio, Colorectal Cancer