BACKGROUND: Adolescents have a unique cancer profile that includes typical childhood cancers such as acute lymphoblastic leukemia (ALL) and adult-type cancers like melanoma and thyroid cancer. In Finland, adolescents above 16 years have been largely treated in adult oncology centers in contrast to many Western countries in which the minimum admittance age is 18 years. The aim of this study was to investigate characteristics, therapy and outcome of cancer in adolescents aged 16 to 17 years. MATERIALS AND METHODS: This retrospective cohort study included adolescents aged 16 to under 18 years at the time of cancer diagnosis between 2000 and 2019 in Tampere University Hospital, a regional tertiary referral center. Clinical data were retrieved from hospital medical records and included diagnosis, clinical and laboratory parameters, therapy and outcome. In addition to standard descriptive statistical analyses, the Kaplan-Meier method and Cox regression modelling were applied to study the outcome and associated factors. RESULTS: A total of 93 patients were diagnosed with a malignant tumour at the age of 16 or 17 years. Males were more often diagnosed with a cancer (62%), while non-CNS (non- central nervous system) solid cancers were the most common entities (76%) and Hodgkin lymphoma was the most common cancer diagnosis (31%). Seventy patients completed their therapy in the referral center and were followed up for a median of 5.4 years. The majority of patients were treated in the adult department (69%). Complete remission was achieved for 89% of patients, while 21% experienced tumor recurrence. The 5-year event-free survival was 65% (95% CI, 54% to 79%) and overall survival 82% (95% CI, 73% to 93%). CONCLUSIONS: The majority of cancers in adolescents of 16 to 17 years of age are solid cancers. Patient outcome in our cohort was favorable and is in line with previously published data.

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In Finland, the incidence of cancer in adolescents aged 15-19 years is 23 per 100,000. 1 The most common types include typical childhood cancers, such as leukaemia, lymphomas and brain tumours, and adult-type cancers, for instance, melanomas and thyroid cancer. 1 Survival rates for children and adolescents with cancer have improved significantly, but patients aged 15-39 years have poorer rates than children for several cancers that affect both groups. 2 Multinational and paediatric-type protocols have been successful in treating adolescents and young adults with acute lymphoblas-