[Haematological malignancies (HM) in Basse-Normandie (BN): incidence and clinical and biological characteristics over the period 1997-2005 in patients less than 25 years old]. / Épidémiologie des hémopathies malignes en Basse-Normandie : incidence et caractéristiques cliniques et biologiques chez l'enfant et l'adulte jeune de moins de 25ans (1997-2005).

BACKGROUND: The study was designed to present the incidence of all the haematological malignancies (HM) in Basse-Normandie (BN) over the period 1997 to 2005 in patients less than 25 years old. BN is an administrative region in the North-West of France, composed of three departments: Calvados, Manche and Orne. We extracted data from the Registre régional des hémopathies malignes de Basse-Normandie, a French registry which belongs to the Association of the French Cancer Registries (Francim). METHODS: All the HM were coded using the third edition of the International classification for oncologic diseases (ICD-O-3). We compared the clinical and biological descriptive data in patients less than 15 years old to those of young adults (15-24 years old). RESULTS: A total of 305 new cases of HM were recorded over the period 1997 to 2005. HM were more frequent in men (168 cases) than in women (137 cases). Patients less than 25 years old accounted for 4.1% of all HM cases, whereas patients less than 15 years old and young adults (15-24 years old) represented 2.2% and 1.9% of all cases, respectively. In patients less than 25 years old, the overall world-standardized incidence rates (WSR) were 7.67/100,000 (95% CI: 6.31-9.04) in BN (8.08 [6.15-10.02] for men and 7.24 [5.31-9.17] for women). In patients less than 15years, the overall WSR was 7.38/100,000 (6.23-8.52), with no difference between boys (7.57) and girls (7.17). Acute lymphoblastic leukaemia (ALL) was the most frequent HM, WSR=4.02/100,000 (3.16-4.88) (4.30 [3.08-5.53] in men, 3.73 [2.52-4.93] in women), with similar clinical and biological criteria between patients less than 15 years and young adults. In young adults, the overall WSR was 8.21/100,000 (7.47-8.96), similar between men and women (9.02 [7.93-10.12] and 7.37 [6.35-8.38], respectively). Their highest WSR was obtained for Hodgkin lymphomas (HL): 3.37/100,000 (2.89-3.85), similar between men (3.49 [2.8-4.17]) and women (3.25 [2.58-3.93]). The study did not show any significant difference between the Calvados, Manche and Orne departments (except for HL, which seems more frequent in Manche department for 15-24 years old cases). There was no evidence of an increased risk for ALL in the subdistricts Beaumont-Hague and Les Pieux, which respectively have a nuclear waste reprocessing plant and a nuclear power plant on their territory. The subtype of HM was dependent on age whereas clinical and biological data were the same, whatever the age. CONCLUSION: These results contribute to HM monitoring in an area where the nuclear industry is present and to improve the organization and follow-up of medical care.