Robert MacLennan

Sunlight: A major factor associated with the development of melanocytic nevi in Australian schoolchildren

BACKGROUND Case-control studies have identified melanocytic nevi (MN) as the most important phenotypic risk factor for melanoma. A knowledge of any environmental factors that cause MN may facilitate prevention of melanoma. OBJECTIVE This study was undertaken to explore the possible role of ambient solar irradiation in the development of MN in children. METHODS With a standard protocol developed after international consultation, the same medical observers examined children in three Australian cities (Melbourne, Sydney, and Townsville) that span a wide range of latitude. RESULTS A total of 1123 Australian schoolchildren 6, 9, 12, and 15 years of age were surveyed. Larger numbers of MN were found (mean 65.4 MN, standard deviation 52.9) than in previous studies of children. Prevalence increased with diminishing latitude (51.1 in Melbourne, 66.5 in Sydney and 77.2 in Townsville), particularly in children 6 and 9 years of age. Although nevus numbers were higher in children with light skin and hair, blue eyes, and freckling, the latitude gradient remained after adjustment for these and other factors in multivariate analysis. CONCLUSION Latitude of residence, and by implication ambient UV radiation, is strongly related to nevus prevalence in young Australian children. However, these differences diminish with age and may disappear by 15 years of age.

Sun exposure and melanocytic naevi in young Australian children

Queensland, Australia, has the highest rates of melanoma in the world and Queensland children have the greatest numbers of melanocytic naevi, the strongest risk factor for melanoma. Although both melanoma and naevi are broadly related to sun exposure in childhood, the relation to individual exposure early in life is difficult to study retrospectively in adults. We surveyed 506 children aged 1-6 years who had been born in Townsville, North Queensland. Sun exposure was assessed by questionnaire and melanocytic naevi were counted using a standard international protocol. Very high counts (upper quarter) of melanocytic naevi were significantly associated with sun exposure of more than 4 hours per day (adjusted relative risk ratio 3.29; 95% Cl 1.12-9.69), and with a history of sunburn (1.89; 1.11-3.21). Melanocytic naevus counts increased with age, light skin reflectance, and freckling. With exposure to intense ultraviolet light in Townsville, children develop melanocytic naevi early in life and in large numbers. We found that both acute and chronic exposure to sun are associated with their development.

Slaked lime and betel nut cancer in Papua New Guinea

Oral squamous cell cancer is the most common malignant tumour in Papua New Guinea. We have found that oral cancer in this region is concentrated at the corner of the mouth and cheek, by striking contrast with western populations, and corresponds precisely with the site of application of lime in 77% of 169 cases. Powdered slaked lime applied to the chewed Areca nut with Piper betle inflorescence at the corner of the mouth causes the mean pH to rise to 10, at which reactive oxygen species are generated from betel quid ingredients in vitro. Reactive oxygen species, together with sustained lime-induced cell proliferation, suggest a possible mechanism of carcinogenesis for this tumour.

SOLAR UVR EXPOSURES OF THREE GROUPS OF OUTDOOR WORKERS ON THE SUNSHINE COAST, QUEENSLAND

The solar ultraviolet radiation (UVR) exposures of three groups of outdoor workers, physical education (PE) teachers, ground staff/gardeners and lifeguards were measured using UVR‐sensitive polysulfone (PS) film badges. The exposures all took place on the Sunshine Coast, Queensland over 5 consecutive weekdays in November 1992. For the three groups, the shoulder badges received greater UVR exposures than the chest badges, in agreement with previous studies. The PE teachers received the highest UVR exposures while the lifeguards received the least. One of the 5 days of the study was overcast with some rain showers and UVR doses for this day for all groups were significantly lower than on the other 4 days, however the ratio of exposure to ambient remained relatively constant. All groups had measured UVR exposures in excess of occupational guidelines, indicating that protective measures, including education and behavior modification, which are becoming much more common in occupational situations in Australia, are both timely and necessary.

Solar UVR Exposures of Primary School Children at Three Locations in Queensland

Abstract— The ultraviolet radiation (UVR) exposures of primary school children in Brisbane, Toowoomba and Mackay (latitudes 27°30′, 27°33′ and 21°15′ south, respectively) were assessed over a period of 2 weeks at each location using UVR‐sensitive polysulfone (PS) film badges attached at the shoulder. The students filled in questionnaires on their time spent outdoors for each day of the study. These data in conjunction with the ambient UVR measured by a detector/datalogger unit at each site were used to correlate the calculated exposures with those measured using the PS badges. Overall, the questionnaires indicated that the males spent more time outdoors and had higher measured UVR exposures than females. For both boys and girls at each location, there was a strong correlation between the mean measured UVR exposure and the ambient solar UVR at that location.

The Eastern Australian childhood nevus study: Prevalence of atypical nevi, congenital nevus-like nevi, and other pigmented lesions

BACKGROUND Various melanocytic lesions are frequently observed. An understanding of phenotypic factors and environmental stimuli that are associated with these lesions may help explain their pathogenesis. OBJECTIVE This study was undertaken to determine the prevalence of atypical nevi, blue nevi, cafe-au-lait macules, congenital nevus-like nevi, halo nevi, nevi spili, nevi 5 mm or more in diameter, and skin-colored melanocytic nevi in a population of schoolchildren and to explore risk factors including solar radiation in the development of these melanocytic lesions. METHODS A cross-sectional study was performed by the same medical investigators to examine schoolchildren in three Australian cities that span a wide range of latitudes. RESULTS Data from 1123 white Australian schoolchildren, 6 to 15 years of age, were analyzed. Acquired melanocytic nevi (atypical nevi, nevi > or = 5 mm in diameter, and skin-colored nevi) were more likely to develop in older fair-skinned subjects who had freckles and lived closest to the equator. Café-au-lait macules and congenital nevus-like nevi were observed in 36.3% and 4.4% of the total population, respectively. Prevalence for both these types of melanocytic lesions increased significantly with decreasing latitude. Halo nevi were present in 5.3% of the subjects and were usually solitary. These lesions were related to the presence of atypical nevi primarily by virtue of their size rather than of other features of clinical atypia. CONCLUSION Like melanocytic nevi in general, large and atypical nevi are strongly influenced by geographic location and, by implication, degree of solar radiation. The same can be said for congenital nevus-like nevi, which suggests that many so-called congenital nevi are in fact acquired early in life.

The Eastern Australian Childhood Nevus Study: Site differences in density and size of melanocytic nevi in relation to latitude and phenotype

It has been postulated that site-specific variation in melanocytic nevus density and size is explained by differential response to sunlight. We observed the density and size of nevi at different body sites in relation to age, phenotype, latitude, and other measures of ultraviolet exposure. A standard protocol was used to assess nevi, phenotype, and sun exposure in 1123 Australian schoolchildren at 3 contrasting latitudes. Associations with phenotype (red hair, skin reflectance, sun sensitivity, and tanning) varied by body site. In Queensland, gender differences in nevus density on the back and lower limbs, unrelated to sun exposure, were similar to gender differences for melanoma. Small nevi (2-4 mm) were most dense on the arms, whereas large nevi (> or =5 mm) were most dense on the posterior trunk where they were related to age, decreasing latitude, male sex, and freckling. Our findings support the hypothesis of site-specific differences in nevus proliferative potential.

Betel quid not containing tobacco and oral cancer: a report on a case-control study in Papua New Guinea and a meta-analysis of current evidence.

Smoking and betel quid chewing are associated with increased risk of oral cancer but few studies have reported on associations in populations where betel quid does not contain tobacco. We conducted a case–control study in Papua New Guinea and a systematic review. Our case–control study recruited 143 cases with oral cancer and 477 controls. We collected information on smoking and betel quid chewing. Current smoking was associated with an increased risk of oral cancer with an adjusted odds ratio (OR) for daily smokers of 2.63 (95% confidence intervals (95% CI) 1.32, 5.22) and amongst heaviest smokers of 4.63 (95% CI 2.07, 10.36) compared to never‐smokers. Betel chewing was associated with increased risk of oral cancer with an adjusted OR for current chewers of 2.03 (95% CI 1.01, 4.09) and in the heaviest chewers of 2.47 (95% CI 1.13, 5.40) compared to nonchewers. The OR in those who both smoked tobacco and chewed betel quid was 4.85 (95% 1.10, 22.25), relative to those who neither smoked nor chewed. The systematic review identified 10 previous studies that examined risk of oral cancer associated with betel quid chewing that controlled for smoking in populations where betel quid did not contain tobacco. In studies that reported results for non‐smokers the combined OR was 2.14 (95% CI 1.06, 4.32) in betel quid chewers and in studies that adjusted for smoking the combined OR was 3.50 (95% CI 2.16, 5.65) in betel quid chewers. Preventive efforts should discourage betel quid chewing as well as smoking.

Accuracy of case-reported family history of melanoma in Queensland, Australia.

A positive family history is used in clinical practice as an indication of increased melanoma risk, yet there are no data on the accuracy of reported family histories of melanoma. The validity of case-reported family history of melanoma was assessed in the course of a family and twin study of melanoma in Queensland, Australia, conducted among the families of 2,118 melanoma cases diagnosed in Queensland between 1982 and 1990. A total of 913 melanoma cases made 1,267 reports of melanoma among their first-degree relatives. A total of 1,040 of these reports were checked, first through relatives themselves and then, if the relative also said they had had melanoma, through the relatives medical records. Medical confirmation of melanoma as the diagnosis was obtained for 623 reports (59.9%; 95% confidence interval 56.9–62.9): a false-positive reporting rate by cases of 40.1%. The level of false-positive reporting was lower for cases under 70 years of age, for women, for cases whose own diagnosis of melanoma was more than 5 years earlier, and for cases with three or more relatives with melanoma. Media campaigns in Queensland aimed at increasing skin cancer awareness, and confusion between melanoma and other more common actinic neoplasms (basal and squamous cell carcinomas), may partly explain the high false-positive reporting rate observed here. For this reason, it is difficult to generalize these findings to northern hemisphere populations where skin cancer is not such an important public health issue.

Sun Exposure and the Incidence of Melanocytic Nevi in Young Australian Children

The number of melanocytic nevi (MN) is an important risk factor for cutaneous melanoma. The present study further investigated the relationship between sun exposure, the incidence of MN, and the prevalence of large acquired MN (≥5 mm). A cohort of 479 preschool children born in Townsville, Australia was examined for MN in 1991 and a year later. Sun exposure was assessed by questionnaire. The erythemally effective dose of solar UV radiation was estimated from questionnaire data combined with local UV biometry. Almost all (97.7%) children had acquired new MN (median, 12), with a median incidence rate of 11.0 per year (interquartile range, 7.0-16.5). Total number of hours of sun exposure during follow-up (P = 0.034) and tendency to burn (P = 0.028) were independent risk factors for MN incidence. Sunburn experience during follow-up failed to reach significance when adjusted for tendency to burn. Lifetime number of sunburns (P < 0.001) and the severity of sunburns experienced during follow-up (P < 0.001) were significantly related to the presence of large acquired MN at follow-up. Reducing the total number of hours of sun exposure is particularly relevant in sun-sensitive children and may restrain the development of MN, whereas avoiding sunburn in young children might prevent large MN, subsequently reducing the risk of melanoma. (Cancer Epidemiol Biomarkers Prev 2008;17(9):2318–24)