A Comparison of Colorectal Cancer in West African and North American Patients: Is the Cancer Biology Different?

Saurabh Saluja, MD, Olusegun I Alatise, MD, Adisa Adewale, MD, Justine Misholy, BA, Joanne Chou, MPH, Mithat Gonen, PhD, Martin Weiser, MD, and T. Peter Kingham, MD


70% of the 24 million people predicted to have cancer by 2050 will live in low- and middle-income countries (LMIC). As a result, cancer care is becoming a priority for healthcare systems in West Africa. This study compares the presentation and pattern of spread of colorectal cancer (CRC) observed in a hospital in West Africa (Nigeria) to that of a North American referral center (New York City).


Data on all adults presenting with CRC at a hospital in West Africa (Nigeria; 1990-2011) and all adults with stages III or IV CRC at a specialty hospital in North America (New York City; 2005-2011) were retrospectively examined. Demographic data, stage of disease, site of metastasis, and survival were compared.


There were 160 patients identified in West Africa and 1,947 patients identified in North America. West African patients were younger (52 vs 59 years, p<0.01) and presented with a later stage of disease (58% stage IV versus 47%, p<0.01). Site of disease presentation was significantly different between West African and North American patients (p<0.01). 2.2% of West African patients presented with liver metastases only, compared to 48.1% of North American patients. Conversely, 61.3% of patients in West Africa presented with peritoneal metastases only, compared to 5.4% in North America. OS stratified by stage at presentation (III/IV) showed worse prognosis for patients in either stage subgroup in Nigeria than North America.


We found differences in the presentation, metastatic pattern, and outcomes of CRC in West Africa when compared to North America. Late detection and differential tumor biology may drive the differences observed between the sites. Future studies on early CRC detection and on tumor biology in LMIC will be critical for understanding and treating CRC in this region.Keywords: Colorectal cancer, Outcomes data, West Africa, Screening, Global Health, Tumor BiologyGo to:


In West Africa, data were obtained from a Nigerian hospital, Obafemi Awolowo University Hospital (OAU). OAU is a tertiary referral hospital with a catchment area of 25 million patients. The charts of all patients diagnosed with CRC between 1990 and 2011 were reviewed by one of the study authors (OIA). Patients without a medical chart present at the time of data collection were excluded. In North America, data were obtained from a prospectively maintained database of all CRC patients treated at a specialty cancer hospital (Memorial Sloan Kettering Cancer Center, MSKCC). These data were crosschecked with a prospectively maintained database of all CRC patients presenting with liver metastases. Patients in this population were included if they presented with or developed a diagnosis of Stage III or IV CRC between 2005 and 2011 and were over age 18. Survival data reflects time from date of diagnosis to death or loss to follow-up. In both sites, follow-up data were limited to patients who continued to seek care at the study hospital. OAU and MSKCC have started an NCI recognized consortium (The African coloRectal cancer GrOup; ARGO) to prospectively build a database and biobank to study colorectal cancer in Nigeria.

In West Africa, staging was performed by physical exam (e.g size of rectal masses, palpable liver lesions), abdominal ultrasound, chest x-ray and laparotomy. In a select group of patients treated in recent years, colonoscopy, diagnostic laparoscopy or CT scan may also have been performed. In the US, staging modalities included physical exam, colonoscopy, endorectal ultrasound, CT scan, MRI and PET scan.

Statistical Methods

Patient demographic data, disease, tumor, and treatment characteristics were compared using Chi-square test for categorical variables or Wilcoxon Rank Sum test for continuous variables. Fisher exact test was used to compare the association between site of metastases to the liver and whether patients presented with obstruction among stage IV patients. Overall survival (OS) was calculated from date of diagnosis/surgery until the time of death. Patients who did not experience the event of interest by the end of the study were censored at the time of the last available follow-up. OS was estimated using the Kaplan-Meier method and the survival probabilities between patients in the two regions were compared using log-rank test.

Time to first recurrence was estimated by cumulative incidence function. The main event of interest was peritoneum recurrence without liver involvement. Stage III patients who had a liver recurrence without peritoneum involvement (N=106), both peritoneum and liver recurrence (N=11), other recurrence without involvement to either liver or peritoneum (N=61) or died without a recurrence (N=52) were considered as competing events. Gray’s test9 was used to test the difference in time to recurrence between the two countries. All P values were based on 2-tailed statistical analysis. All analyses were performed with SAS version 9.3 (SAS institute, Cary, North Carolina) and R (version 10.2).Go to:


There were 160 patients identified at the West African center and 1,947 patients identified at the North American center. Patients in West Africa were significantly younger (52 vs 59 years, p<0.01) and more commonly male (61% vs 52%, p<0.01) (Table 1). Seven percent of North American patients were African American. In the West African dataset, 144 of the patients had complete data describing which surgical procedure was performed. In the North American dataset, 1,657 patients had complete data describing which surgical procedure was performed. West African patients more commonly presented with rectal primary tumors (53% vs 32.3%, p<0.01) and had a bowel obstruction as a presenting symptom (45% vs 28%, p<0.01). In West Africa, 41% of patients presented with stage III disease and 58% presented with stage IV disease, whereas in North America, where the study population was limited to stage III and IV disease, the population was nearly evenly divided between stages. 49 (2.5%) patients in North America entered the study period with stage II cancer and subsequently developed metastases whereas one patient in West Africa entered the study period with stage I cancer and developed metastases.