Melanocytic Nevi, Ambient UV Exposure And Thyroid Cancer Risk: The French E3N Prospective Cohort

Marina KVASKOFF, Gustave Roussy, France
MESRINE S. 1,2,3 , BAH T. 1,2,3 , WALD L. 4 , CLAVEL-CHAPELON F. 1,2,3 , BOUTRON-RUAULT M. 1,2,3

1 Inserm, CESP, U1018, Generations and health, F-94805, Villejuif, France
2 Univ Paris Sud, Univ Paris-Saclay, UMRS 1018, F-94805, Villejuif, France
3 Gustave Roussy, F-94805, Villejuif, France
4 MINES ParisTech, PSL-Research University, O.I.E. Centre Observation, Impacts, Energy, CS10207, F-06904, Sophia Antipolis, France

Purpose: Incidence rates have considerably increased worldwide for both differentiated thyroid cancer (DTC) and cutaneous melanoma, and two-way associations between these neoplasms have been described. Whether melanoma risk factors such as ultraviolet (UV) exposure and pigmentary traits are associated with DTC risk remains unknown.

Methods: Using Cox regression modeling, we prospectively analyzed the relations between self-reported pigmentary traits, childhood and adulthood residential UV exposure, and risk of DTC in 91,082 women from the E3N cohort, who were followed-up over 1990-2008 through biennial questionnaires. We used logistic regression modeling to assess associations of pigmentary traits and UV exposure with personal history of benign thyroid diseases. All statistical tests were two-sided.

Results: In models adjusted for age and DTC risk factors, number of nevi was positively associated with DTC risk (“very many” vs. “none”: Hazards Ratio=1.67, 95% Confidence Interval=1.03–2.73; Ptrend=0.01), independently of residential UV exposure or iodine intake. DTC risk was inversely associated with latitude (Ptrend=0.03) and positively associated with mean daily UV dose (Ptrend=0.02) at baseline, but not at birth, and only in women with dietary iodine below the median intake. Personal histories of dysthyroidism and of goiter/nodules were positively associated with number of nevi (Ptrend=0.0001 for both) and mean daily UV dose at baseline (Ptrend=0.0001 and 0.0003, respectively).

Conclusions: Our results suggest that number of nevi and residential UV exposure are associated with the risks of DTC and benign thyroid conditions. They point to novel pathways in thyroid cancer or melanoma etiologies and warrant replication.

Funding source: This work was supported by the Mutuelle Générale de l’Education Nationale (MGEN); the European Community; the French League against Cancer (LNCC); Gustave Roussy, the French National Institutes for Health and Medical Research (Inserm) and the French National Cancer Institute (InCA) (#2009-139). MK is supported by a Marie Curie Fellowship (#PIOF-GA-2011-302078)