Epidemiology of Cancers in Adolescents and Young Adults in Nigeria

In recent times, there has been an increasing need to prioritise cancers in adolescents and young adults, who are individuals aged 15-39 years at cancer diagnosis, due to their unique cancer biology, cancer predisposing factors and cancer epidemiology, peculiar economic, psychological and social needs, heterogeneity of the population, delayed and missed diagnosis, limited clinical trial participation and special survivorship issues.^1-2,3,4 In addition, AYAs present with a distinct clinical need for fertility preservation and incorporating fertility-sparing options is critical to safeguarding reproductive functions.²

The incidence of cancers among adolescents and young adults (AYAs) has increased over the years, while the survival rates, on the other hand, though slightly improved, lag behind those achieved in paediatrics and older adults.^1,3,5,6 Also, the spectrum of adolescent and young adult cancers differs from those in paediatric and older adults and varies with age, ethnicity and geographical locations.^1-6 Haematological malignancies, breast cancer, thyroid cancer, bone and soft tissue cancers, colorectal cancer, CNS tumours, germ cell tumours, cervical cancer and melanoma are common in adolescents and young adults.^1,4,5,6

In 2022, adolescents and young adults made up about 40% of Nigeria's population.⁷ Despite this, studies on adolescent and young adult oncology patients in Nigeria are scarce. This study aims to describe the epidemiological distribution of cancers in adolescents and young adults in Nigeria, which would guide targeted policies, guidelines, research and interventions specific to cancer control in this population.

Data on all adolescents and young adults were extracted from a publication by the Nigerian National System of Cancer Registries, Federal Ministry of Health of Nigeria, on Cancer in Nigeria.⁸ The publication contains data from 14 cancer registries (7 population-based [PB] and 7 hospital-based [HB]) out of 30 cancer registries (10 population-based and 20 hospital-based) in Nigeria, from 2009 to 2016. Five cancer registries were located in Northern Nigeria (Abuja Cancer Registry; PB, [2009-2016], Maiduguri Cancer Registry; PB, [2016], FMC Gombe Cancer Registry; HB, [2009-2016], FMC Keffi Cancer Registry; HB, [2009-2016], and Sokoto Cancer Registry; PB, [2014-2015]) while 9 were in Southern Nigeria (NAUTH Cancer Registry; HB, [2009-2016], FMC Yenagoa; HB, [2009-2016], Calabar Cancer Registry; PB, [2009-2016], Benin Cancer Registry; PB, [2014-2016], Ekiti Cancer Registry; PB, [2014-2016], Enugu Cancer Registry; PB, [2012-2016], LASUTH Cancer Registry; HB, [2009-2016], LUTH Cancer Registry; HB, [2009-2016] and UPTH Cancer Registry; HB, [2009-2016]).[Figure 1] Other details describing the registry coverage, case ascertainment/primary data sources are shown in Table 1.

The data extracted was analysed using SPSS version 25. Frequencies, percentages, tables, and charts were used to represent and present the results. The association between categorical variables (age group, sex, and region) was tested using the Chi-squared test, which met the required assumptions.

This study utilised secondary analysis of fully anonymised, de-identified and publicly available data derived from a publication by the Nigerian National System of Cancer Registries, Federal Ministry of Health of Nigeria, on Cancer in Nigeria (Available from: https://www.ncbi.nlm.nih.gov/books/NBK581073/).⁸ Individual patient confidentiality was preserved throughout the research as there were no direct or indirect personal identifiers in the dataset.

A total of 7,143 cancer cases seen within the study period occurred among adolescents and young adults (AYAs), accounting for 24.2% (≈1 in 4) of cancer cases in Nigeria. In Northern and Southern Nigeria, cancer in AYAs accounted for 28.7% and 22.2% of cancer cases, respectively. Among female patients with cancers, AYAs accounted for 27.9% of cases (32.1% and 26.2% in the North and South, respectively), while among male cancer patients, AYAs accounted for 17.7% of cases (23.4% and 14.8% in Northern and Southern Nigeria, respectively) [Figure 2].

Females constituted 73.5% of AYAs with cancer, with a male-to-female ratio of ≈1:3. The proportion of female AYAs with cancer was higher in the south compared to the north (76.7% and 67.9%, X²=66.241, 95%CI=0.58-0.71, p=0.000), and the male-to-female ratio was ≈1:3 and ≈1:2 in Southern and Northern Nigeria, respectively [Table 2].

About two-thirds (65.7%) of cancers in AYAs occurred among those within the age group 30-39 years. The proportion of AYAs with cancers within age group 15-19 years and 20-29 years were higher in the north (6.4% and 29.9% respectively) compared to the south (5.1% and 28.1% respectively), while the proportion of AYAs within age group 30-39 years was higher in the south compared to the north (66.8% and 63.6% respectively, X²=9.653, 95%CI=0.01-0.06, p=0.008) [Table 2]. Similarly, the proportion of AYAs with cancer within age group 15-19 years and 20-29 years was significantly higher among the males compared to the females, while the proportion of AYAs within age group 30-39 years was higher among the females both nationwide (X²=213.471, 95%CI=0.15-0.20, p=0.000) and across the two geographic regions(X²=33.632, 95%CI=0.08-0.15, p=0.000 and X²=204.478, 95%CI=0.18-0.24, p=0.000, in the North and South respectively) [Table 3].

The number of cancer cases among AYAs increased rapidly from ages 20-25 years and peaked among those 35-39 years; however, this rapid increase was more among females compared to males [Figure 3A].

The most common cancers in AYAs in Nigeria were breast cancer (37.4%), bone and soft tissue cancer (7.2%), cervical cancer (5.4%), lymphomas (4.7%), ovarian cancer (4.5%) and colorectal cancer (4.5%) [Table 4]. While breast cancer (30.5%), bone and soft tissue cancer (6.8%), non-melanoma skin cancer (NMSC) (6.5%), liver cancer (6.4%), cervical cancer (6.0%) and colorectal cancer (5.1%) were the most common cancers in the north, breast cancer (41.4%), bone and soft tissue cancer (7.4%), lymphomas (5.3%), cervical cancer (5.1%), ovarian cancer (4.4%) and colorectal cancer (4.1%) were the most common in the south [Table 5].

Among female AYAs, Breast, cervical and ovarian cancers were the most common cancers nationwide (50.3%, 7.4% and 6.2%, respectively), as well as the most common cancers in northern Nigeria (44.2%, 8.8% and 7.1%, respectively) and southern Nigeria (53.4%, 6.7% and 5.7%, respectively). Among males, bone and soft tissue cancer (14.8%), liver cancer (11.0%) and colorectal cancer (9.2%) were the most common cancers in Nigeria. In northern Nigeria, liver cancer (14.2%), bone and soft tissue cancer (12.5%) and NMSC (10.7%) were the most common cancers among the male AYAs while bone and soft tissue cancer (16.7%), lymphomas (10.1%) and colorectal cancer (9.3%) were the most common among male AYAs in southern Nigeria [Table 6A-C, see supplementary data for Tables 6B and 6C].

Bone and soft tissue cancer, lymphomas and NMSC were the most common cancers among AYAs within the age group 15-19 years in Nigeria (22.4%, 13.3% and 8.3%, respectively), northern Nigeria (18.7%, 12.0% and 10.2%, respectively) and southern Nigeria (25.0%, 14.2% and 6.9%, respectively). Among AYAs within the age group 20-29 years, breast cancer (26.7%), bone and soft tissue cancer (10.5%) and lymphomas (6.5%) were the most common cancers in Nigeria. While breast cancer, bone and soft tissue cancer and NMSC were the most common cancers among AYAs aged 20-29 years in northern Nigeria (21.5%, 9.9% and 7.9% respectively), breast cancer (29.8%), bone and soft tissue cancer (10.8%) and lymphomas (8.1%) were the most common cancers among AYAs within the same age group in southern Nigeria. Breast cancer, cervical cancer and bone and soft tissue cancer were the most common malignancies among AYAs aged 30-39 years nationwide (45.1%, 6.9% and 4.5% respectively) and in southern Nigeria (49.1%, 6.7% and 4.75 respectively), while breast cancer (37.7%), cervical cancer and liver cancer were the most common malignancies among AYAs between 30-39 years in the north [Table 7A-C, see supplementary data for Tables 7B and 7C].

There was an increase in the incidence of cases of the common cancers among AYAs with increasing age, except for bone and soft tissue cancer, which had a slight decline after age 25-29 years [Figure 4].

This study set out to evaluate the national burden of cancers in AYAs in Nigeria, as well as describe the epidemiological distribution of cancers in AYAs in Nigeria by sex, age and geographical location.

AYA cancers accounted for about 1 in 4 (24.2%) of all cancer cases in Nigeria within the study period. This finding differed from those of studies conducted in the United States of America (USA) and Europe, which reported that cancers in AYAs accounted for 4.2% (≈ 1 in 24) and 5.0% (1 in 20) of all cancer cases, respectively.^{5, 9} The proportion of AYA cancers in Nigeria was about 6 and 5 times higher than the proportion of AYA cancers in the USA and Europe. This could be due to the high proportion of AYAs in the Nigerian population⁷ as well as the early occurrence of some common malignancies at an earlier age in blacks.^10,11 Our study revealed that the proportion of AYA cancers in Northern Nigeria was significantly higher than that in Southern Nigeria (28.7% and 22.2%, respectively, p<0.001). This could be due to underestimation as a result of fewer reported cases, as well as a lower number of registries in the North compared to the South.

Females accounted for about three-quarters of cancers in AYAs, with a male-to-female ratio of ≈1:3. The sex distribution of breast cancer, the most common malignancy in Nigeria, could explain the skewed sex distribution of AYA cancers. Studies done by Li et al and Trama et al also demonstrated similar findings of female preponderance of AYA cancers with a male-to-female ratio of 1:2.^{6, 9} Across Northern and Southern Nigeria, female AYAs with cancers were more than the male AYAs; however, the proportion of female AYAs with cancers was significantly higher in the South than in the North (76.7% and 67.9%, respectively, p=0.000)

A higher proportion of AYAs with cancer (65.7%) occurred among those between 30 and 39 years. A similar age distribution was also noticed across Northern and Southern Nigeria (63.6% and 66.8%, respectively). These findings were in Tandem with those from previous studies, which reported that AYAs within the ages of 30 and 39 years accounted for about 65.7% - 68.3% of AYA cancers.^12-14 This is not unexpected, as the incidence of cancers increases with increasing age. However, this increase was more rapid among the females compared to the males, and this further explains the reason for the female preponderance. The proportions of AYAs with cancers within the ages 15-19 years and 20-29 years were higher among the males as well as among the Northerners compared to the females and the Southerners. A similar age distribution among sexes was reported in the USA by Scot et al.¹³ Furthermore, the male-to-female ratio varied with increasing age, from ≈1:1 among those 15-19 years, to ≈1:2 among those 20-29 years, to ≈1:4 among those 30-39 years. These findings suggest the earlier occurrence of AYA cancer among males compared to females, and buttress the heterogeneity of cancers in AYAs by age, sex and geographical location.

Breast cancer, bone and soft tissue cancers, cervical cancer and lymphomas were the most common cancers in AYAs in Nigeria. This finding differed slightly from that reported by Li et al, who revealed that breast cancer, thyroid cancer, cervical cancer and lymphomas were the most common malignancies in AYAs globally.⁶ Also, the National Cancer Institute (NCI) and Trama et al reported breast cancer, thyroid cancer, testicular cancer and melanoma as the most common cancers among AYAs in the USA and Europe.^5,9 Within Nigeria, AYAs' malignancies varied based on geographical location. While breast cancer, bone and soft tissue cancers, non-melanoma skin cancer (NMSC) and liver cancer were the most common AYA cancers in the North, breast cancer, bone and soft tissue cancers, lymphomas and cervical cancers were the most common AYA cancers in the South. The difference could be due to variation of risk factors (genetic and environmental) based on geographical location.

In our study, breast cancer, cervical cancer and ovarian cancer were the most common malignancies among female AYAs, while bone and soft tissue cancers, liver cancer and colorectal cancer were the most common among male AYAs. This finding corroborates the variation of AYA cancers based on sex as reported by a global population-based study in AYA malignancies by Li et al.⁶ They demonstrated that breast cancer, thyroid cancer and cervical cancer were the most frequently diagnosed AYA cancers in females, while thyroid cancer, lymphomas and testicular cancer were the most frequently diagnosed in male AYAs.⁶ In the USA, AYAs' cancer also varied based on sex, as breast cancer, thyroid cancer and melanoma were the most common among female AYAs, while testicular cancer, lymphomas and colorectal cancer were the most common among male AYAs.⁵ Worthy of note is that the high burden of thyroid cancer among AYAs in the USA and the global population, compared to the findings from our study. This could be due to differences in thyroid cancer risk factors (genetic and environmental), as well as differences in thyroid cancer diagnosis practices, which could lead to under-diagnosis and underestimation of thyroid cancer in our setting. Breast cancer was the most common cancer among female AYAs in both Northern and Southern Nigeria. However, among male AYAs, liver cancer was the most common in the North, while bone and soft tissue cancers were the most common in the South. This could be due to variation in risk factors of liver cancer across both regions. Musa et al demonstrated that the prevalence of hepatitis B virus infection was higher in Northern Nigeria compared to the South.¹⁵

Bone and soft tissue malignancies, lymphomas and NMSC were the most common cancers among AYAs aged 15-19 years. Breast cancer, bone and soft tissue cancers and lymphomas were the most common among AYAs aged 20-29 years, while breast cancer, cervical cancer and bone and soft tissue cancers were the most common among AYAs aged 30-39 years. These findings were in tandem with reports from other studies by Li et al and Miller et al, which also demonstrated age variation of AYA cancers.^6,12 Li et al reported Leukaemia, thyroid cancer and breast cancer as the most common malignancies among AYAs aged 15-19 years, 20-29 years and 30-39 years respectively,⁶ while Miller et al reported lymphoma, thyroid cancer and breast cancer as the most common malignancies among AYAs aged 15-19 years, 20-29 years and 30-39 years respectively.¹² The age variation of AYA cancers was fairly similar in both the Northern and Southern parts of Nigeria.

The most common cancer in AYAs in Nigeria was breast cancer, accounting for 37.4% of cancers in AYAs (30.5% in the North and 41.1% in the South). Breast cancer was also the most common among female AYAs as well as among AYAs between the ages of 20-29 years and 30-39 years in Nigeria. AYAs accounted for ≈ 1 in 4 (30.4%) of all breast cancer cases in Nigeria (≈ 1 in 3 in the North and ≈ 2 in 7 in the South). Most of the breast cancer cases in AYAs in Nigeria occurred among those between the ages of 30-39 years, and 1.3% occurred among males (1.5% in the North and 1.2% in the South).

The second most common cancers in AYAs in Nigeria were bone and soft tissue cancers, accounting for 7.2% of cancers in AYAs (6.8% in the North and 7.4% in the South). Bone and soft tissue sarcomas were also the most common cancers among male AYAs, as well as among AYAs between 15 to19 years. AYAs accounted for ≈ 2 in 5 (42.5%) of all cases of bone and soft tissue cancers in Nigeria (≈ 2 in 5 in both Northern and Southern Nigeria, respectively). The male-to-female ratio was 1:0.8, indicating a slight male preponderance (1:0.7 in the North and 1:0.9 in the South). Most bone and soft tissue cancers occurred among AYAs aged 20-29 years (20-29 years in Northern Nigeria and 30-39 years in Southern Nigeria).

Cervical cancer was the third most common cancer in AYAs in Nigeria (fifth in the North and fourth in the South), accounting for 5.4% of AYA cancers (6.0% in the North and 5.1% in the South). It was the second most common malignancy among female AYAs. AYAs accounted for about 2 in 15 (13.4%) of all cases of cervical cancer in Nigeria (≈1 in 6 in the North and ≈ 2 in 17 in the South). Most of the AYA cervical cancer cases occurred among AYAs between the ages of 30-39 years, and the incidence of cases increased with increasing age.

Lymphomas (Hodgkin and non-Hodgkin lymphomas) were the fourth most common cancers in AYAs in Nigeria (ninth in the North and third in the South), accounting for 4.7% of AYA cancers (3.6% in the North and 5.3% in the South). Lymphomas ranked fourth and sixth in cancer cases in male and female AYAs, respectively, with fairly equal sex distribution. About 1 in 3 of all lymphomas in Nigeria occurred among AYAs (1 in 3 in both Northern and Southern Nigeria). A higher proportion of AYAs with lymphoma occurred among those in the age group 30-39 years.

Ovarian cancer was the fifth most common cancer among AYAs in Nigeria (7th in the North and 5th in the South), accounting for 4.5% of AYA cancers (4.8% in the North and 4.4% in the South). It was the third most common cancer among female AYAs in Nigeria. About 1 in 3 of all ovarian cancer cases in Nigeria occurred among AYAs (≈ 2 in 5 in the North and ≈ 1 in 3 in the South). Over half of the cases of ovarian cancer in AYAs occurred among those between 30-39 years.

The 6th most common AYA cancer in Nigeria was colorectal cancer, accounting for 4.5% of AYA cancers (5.1% in the North and 4.1% in the South). About 1 in 5 cases of colorectal cancer in Nigeria occurred among AYAs (≈ 2 in 7 in the North and ≈ 2 in 11 in the South). There was a slight male preponderance of colorectal cancer in AYAs with a male-to-female ratio of 1:0.8 (1:0.7 in the North and 1:0.9 in the South).

This study used data published from cancer registries in Nigeria; hence, the accuracy depends on the data reported by the cancer registries. Challenges documented from the publication about the data from the cancer registries were data availability, data inconsistency, data insufficiency and data quality concerns. Some reasons for these challenges include: industrial actions, lack of sufficient manpower, lack of funding, inefficiency of registry personnel and Boko Haram insurgency⁸ which could lead to underestimation of cancer burden and a distorted public health trend. In addition, information about the completeness/quality metrics and management of duplicate data was not available. Data from 7 seven hospital-based cancer registries were used, and may not be representative of true cancer distribution in the general population. Also, hospitals with specialised oncology centres will show artificially high numbers of cancers, especially rare cancers, due to selection bias. Furthermore, as patients move from cities/states to hospitals with specialised oncology centres, this skews the data, making it difficult to ascertain the geographic origin of the cancer cases. It also leads to duplication of cancer registrations, as there is no unified cancer registry database in the Country as of the time of writing this article. While most of the cancer cases were diagnosed with histology/cytology, some of the diagnoses were based on clinical, radiological and laboratory diagnosis, which may affect the data quality, increase the risk of diagnostic inaccuracy and mask disparity across geographic regions. Furthermore, Procedures used for handling multiple primaries, validating age and sex or missing/unspecified values were not stated. In addition, the cancer registry data currently available for Nigeria were collected from 2009 to 2016, and this may not represent the current epidemiological status of AYA cancers in Nigeria. Also, the use of 2009-2016 data would fail to demonstrate demographic shifts, fail to reflect modern diagnostic advances and changes in tumour classification, and fail to reflect current changes in registry infrastructure. Furthermore, data on cancer survivorship were not available. Despite these limitations, this study presents a comprehensive epidemiological picture of cancers in AYAs in Nigeria using available registry data.

Cancers in AYAs accounted for about 1 in 4 (24.2%) of cancers in Nigeria, with a male-to-female ratio of about 1:3 and most cancers in AYAs occurred among those within the age group 30-39 breast cancer was the most common cancer among females, while bone and soft tissue cancers were the most common among male. The occurrence of AYA cancers in Nigeria varied based on sex, age group and geographical location.

The authors declare that they have no conflict of interest.

No specific funding was received for this work.

This study was a secondary analysis of aggregated, de-identified data obtained from the publicly available report Cancer in Nigeria: 2009–2016, published by the Nigerian National System of Cancer Registries. The investigators had no access to individual-level records or direct or indirect patient identifiers. Because the study involved only analysis of publicly available, aggregated data and did not constitute human-participant research, institutional ethics committee approval was not required.

Informed consent was not applicable because no participants were recruited or contacted, and the investigators analyzed only publicly available, aggregated data containing no identifiable patient information.

Not applicable. No direct participant enrollment or prospective data collection occurred.

All authors contributed to the study conception and design. Data collection was done by Chiamaka G Ehiedu, Olabisi T Ojo, and Abel S Anegbe under the supervision of Ayorinde M Folasire, Adebayo A Oladeji, Ajibike A Orekoya and Atara I Ntekim. The draft preparation was made by Chiamaka G Ehiedu and Olabisi T Ojo, reviewed and edited by the supervisors. The final manuscript represents the aggregate of revisions and adjustments by all the authors. All authors agreed on the publication of the manuscript.

1. Adolescent and Young Adult Oncology Progress Review Group. Closing the Gap: Research and Care Imperatives for Adolescents and Young Adults with Cancer. NIH Pub. No. 06-6067. National Institutes of Health; 2006. Accessed July 12, 2025. http://cancer.gov/types/aya/research/ayao-august-2006.pdf

2. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Adolescent and Young Adult (AYA) Oncology. Version 2.2024. Published July 7, 2023. Accessed July 12, 2025. https://www.nccn.org/guidelines/guidelines-detail?category=4&id=1412

3. Ferrari A, Stark D, Peccatori FA, et al. Adolescents and young adults (AYA) with cancer: a position paper from the AYA Working Group of the European Society for Medical Oncology (ESMO) and the European Society for Paediatric Oncology (SIOPE). ESMO Open. 2021;6(2):100096. doi:10.1016/j.esmoop.2021.100096

4. Canadian Partnership Against Cancer. Adolescents & Young Adults with Cancer: A System Performance Report. Canadian Partnership Against Cancer; 2017. Accessed July 2, 2025. https://s22457.pcdn.co/wp-content/uploads/2019/01/Adolescents-and-young-adults-with-cancer-EN.pdf

5. National Cancer Institute. SEER Cancer Stat Facts: Cancer Among Adolescents and Young Adults (AYAs). Surveillance, Epidemiology, and End Results Program. Accessed July 16, 2025. https://seer.cancer.gov/statfacts/html/aya.html

6. Li W, Liang H, Wang W, et al. Global cancer statistics for adolescents and young adults: population-based study. J Hematol Oncol. 2024;17(1):99. doi:10.1186/s13045-024-01623-9

7. National Bureau of Statistics. Demographic Statistics Bulletin 2022. National Bureau of Statistics; 2022. Accessed June 21, 2025. https://www.nigerianstat.gov.ng/elibrary/read/1241422

8. Akintola A, Odutola M, Olayinka T, Akinjiola A, Nwokwu UE, Adebamowo C, eds. Cancer in Nigeria: 2009-2016. Nigerian National System of Cancer Registries; 2021. Accessed [date needed]. https://www.ncbi.nlm.nih.gov/books/NBK581073/

9. Trama A, Stark D, Bozovic-Spasojevic I, et al. Cancer burden in adolescents and young adults in Europe. ESMO Open. 2023;8(1):100744. doi:10.1016/j.esmoop.2022.100744

10. Hendrick RE, Monticciolo DL, Biggs KW, Malak SF. Age distributions of breast cancer diagnosis and mortality by race and ethnicity in US women. Cancer. 2021;127(23):4384-4392. doi:10.1002/cncr.33846

11. Siegel RL, Miller KD, Jemal A. Cancer statistics, 2020. CA Cancer J Clin. 2020;70(1):7-30. doi:10.3322/caac.21590

12. Miller KD, Fidler-Benaoudia M, Keegan TH, Hipp HS, Jemal A, Siegel RL. Cancer statistics for adolescents and young adults, 2020. CA Cancer J Clin. 2020;70(6):443-459. doi:10.3322/caac.21637

13. Scott AR, Stoltzfus KC, Tchelebi LT, et al. Trends in cancer incidence in US adolescents and young adults, 1973-2015. JAMA Netw Open. 2020;3(12):e2027738. doi:10.1001/jamanetworkopen.2020.27738

14. Darling HS, Mohan R, Sud R. Epidemiology of cancer in adolescents and young adults from a tertiary care hospital in Southern India. J Cancer Res Ther. 2023;19(7):2036-2044. doi:10.4103/jcrt.jcrt_1185_22

15. Musa BM, Bussell S, Borodo MM, Samaila AA, Femi OL. Prevalence of hepatitis B virus infection in Nigeria, 2000-2013: a systematic review and meta-analysis. Niger J Clin Pract. 2015;18(2):163-172.