How ethnicity is fueling breast cancer in Kenya-Aga Khan University Hospital, Nairobi

By Gatonye Gathura

A large study involving 11 hospitals throughout Kenya shows breast cancer is highly influenced by local ethnic characteristics and habits.

The study shows more breast cancer among women in ethnic communities with low female education, early pregnancies and obesity promoting lifestyles.

It also shows farmer women at higher risk while suggesting that Nilotes may be facing a more aggressive breast cancer than other ethnic groups.

The study: Ethnicity and breast cancer characteristics in Kenya, covered 846 breast cancer patients from public, private and faith based hospital across the county

In the three –year project coordinated by the Aga Khan University Hospital, Nairobi researchers studied breast cancer among Kenya’s three major ethnic groups of Bantus, Nilotes and Cushites.

The study published on 26th September says the types of breast cancers affecting women across all the ethnic groupings are largely similar.

However, the cancers were found to be associated with certain social characteristics among the ethnic groups.

For example affected Bantus were most likely to be more overweight or obese, older at first pregnancy, and younger at menopause compared to the other groups.

Most of the Bantu women, the report says were likely to be working in the farms compared to Nilotes who were most likely in formal employment or housewives.

Although the study does not explain the association of breast cancer to farming, it is likely a co-incidence, however   other studies have pointed to possible exposure to pesticides and development of certain cancers.

“We also found Nilotes to more likely present with larger tumors compared to the other groups,” explained Dr Shahin Sayed, of Aga Khan University Hospital who was the lead investigator.

She explained they are not yet clear whether larger tumors among the Nilotes reflected a type of aggressive tumor or was due to late presentation and diagnosis in this group.

“On average we found that patients from the most highly educated group had the smallest tumors most probably because they are likely to seek health care much earlier.”

But due to the smaller number of Nilotes in the study, the researcher explained they were not able to determine conclusively whether they were at risk of developing a more aggressive type of breast cancer from other groups.

“This is an area in which we recommend further studies,” said Dr Sayed in an interview on Tuesday.

Affected Nilotes were significantly less overweight or obese, younger at first pregnancy, and older at menopause in comparison with the Bantus.

On the other hand the Cushites, the report shows were likely to be diagnosed with breast cancer at younger ages than the other ethnic groups.

The greatest proportion of the Cushites, 56 per cent had a first pregnancy by age 20 compared with 35 per cent of Nilotes and 24 per cent of Bantus.

“Early marriages and subsequent early pregnancies could contribute to the higher proportion of early-onset premenopausal breast cancers seen in the Cushites versus the other two ethnic groups,” said Dr Sayed.

An interesting finding in the study is that a vast majority of women, 92 per cent did not report any history of breast cancer in the family.

Reported in the journal Breast Cancer Research and Treatment the study largely confirms findings published last year by the Nairobi Cancer Registry which had linked various cancers to tribal origins and habits.

The earlier findings were reported by a team of scientists who took time to study medical records of patients who had died from cancer in Nairobi going back 15 years.

The combined team of six researchers from Kenya Medical Research Institute (Kemri), Britain’s Queen Mary University and Oxford University came to striking conclusions linking the occurrence of cancer in Nairobi to the tribal origin and habits of afflicted people.

The new study recruited 846 breast cancer patients including 661 Bantus, 143 Nilotes, 19 Cushites, and 23 breast cancer patients of mixed ethnicity.

Nilotic-speaking tribes in the country comprise the Luo, Maasai, Pokot, Samburu, Turkana, and many of the subgroups which constitute the Kalenjin.

They occupy the vast areas of western Rift Valley, which skirts the border of Uganda from Sudan in the north to Tanzania in the south.

Some of the bigger Bantu groups include the Kikuyu, the Kamba, the Luhya, the Kisii, the Meru, and the Mijikenda. The Swahili people are descended from Mijikenda Bantu peoples that intermarried with Arab and Persian immigrants.

The Somali, Rendile, Oromo, and Borana are some of the larger Cushitic ethnic community who reside in the semi-arid and arid North Eastern regions of Kenya.

To qualify for inclusion as a pure ethnic group in the study, the parents and both grandparents of the breast cancer patient had to belong to the same ethnic group.

“If all maternal and paternal grandparents and parents did not belong to the same ethnic group, that patient’s ethnicity was categorized as mixed.”

According to the Nairobi Cancer Registry, breast cancer is the most common malignancy in Kenyan women, accounting for 23 per cent of all incident cases


Participating health facilities


  1. Aga Khan University Hospital, Kenya
  2. AIC Kijabe Hospital
  3. Mary’s Mission Hospital, Nairobi
  4. Nyeri Provincial General Hospital
  5. Kenyatta National Hospital
  6. Garissa Provincial General Hospital
  7. Coast Provincial General Hospital
  8. New Nyanza Provincial General Hospital
  9. Tenwek Hospital, Kenya
  10. Aga Khan Hospital Mombasa
  11. Aga Khan Hospital Kisumu


Other institutions

African Population and Health Research Centre (APHRC), Nairobi

University of Alabama at Birmingham, US

National Cancer Institute, Bethesda, US

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