Background: Cancers in adolescents and young adults (AYAs; ages 15–39 years) differ from those in children and older adults. AYAs with cancers have received less research focus over the years despite their unique medical, psychological, socioeconomic and sexual concerns. The burden of cancer among this age group in Nigeria is unknown. This study aims to determine the pattern of cancers in AYAs seen in a radiation oncology clinic in Nigeria.

Method: A retrospective study among AYAs (15–39 years) with cancer who presented at a Radiation Oncology Clinic in Nigeria between January 2018 and December 2023.

Results: There were 529 new cancer cases among AYAs, accounting for 14.1% of all cancer cases seen during the period. The male-to-female ratio was 1:3. The majority (72.8%) were in the 30–39 age range, with a mean age of 32.06 ± 6.18 years. Females had a higher mean age (33.01 ± 5.31 years) than males (29.43 ± 7.57 years) (p < 0.001). Breast (39.1%), bone and soft tissue (12.9%) and cervix (11.6%) were the most common sites of cancer in AYAs. Among the males, bone and soft tissue (20.0%), nasopharynx (13.6%) and sinonasal (10.7%) were the most common sites, while breast (52.2%), cervix (15.4%) and bone and soft tissue (10.0%) were the most common sites among females.

Conclusion: AYAs accounted for 14.1% of all new cancer cases. Breast cancer was the most common cancer among female AYAs, while bone and soft tissue cancers were the most common among males.