Melanoma risk and residence in sunny areas. EORTC Melanoma Co-operative Group. European Organization for Research and Treatment of Cancer

Analysing the causal relationship between potentially protective and risk factors and cutaneous melanoma: A Mendelian randomization study

BACKGROUND

Previous observational studies reported altered melanoma risks in relation to many potential factors, such as coffee intake, smoking habits and photodamage-related conditions. Considering the susceptibility of epidemiological studies to residual confounders, there remains uncertainty about the actual causal roles of these reported factors in melanoma aetiology.

OBJECTIVES

This study aims to investigate the causal association between cutaneous melanoma (CM) and previously reported factors: coffee intake, alcohol consumption, lifetime smoking, socioeconomic status (SES), ease of skin tanning, childhood sunburn and facial ageing, providing insight into its underlying aetiology and preventative strategies.

METHODS

We utilized a two-sample MR analysis on data from the largest meta-analysis summary statistics of confirmed cutaneous melanoma including 30,134 patients. Genetic instrumental variables were constructed by identifying single nucleotide polymorphisms (SNPs) that associate with corresponding factors. Inverse variance weighted (IVW) was the primary MR method. For sensitivity and heterogeneity, MR Egger, weighted median, simple mode, weighted mode and MR Egger intercept tests were examined.

RESULTS

Cutaneous melanoma risks were found to be elevated in association with a predisposition towards ease of skin tanning (IVW: OR = 2.842, 95% CI 2.468-3.274, p < 0.001) and with childhood sunburn history (IVW: OR = 6.317, 95% CI 4.479-8.909, p < 0.001). Repeated MR after removing potential confounders and outliers demonstrated resolved horizontal pleiotropy and statistically significant results that closely mirrored the initial findings. Other potential factors, such as coffee intake, alcohol consumption, smoking and socioeconomic status (SES), indicated insignificant effects on melanoma risk in the analysis, and therefore, our Mendelian randomization study does not support their roles in modifying melanoma risks.

CONCLUSIONS

Our extensive MR analysis provides strong evidence of the causative role of ease of skin tanning and childhood sunburn history in elevating melanoma risk. Curtailing ultraviolet radiation (UVR) exposure may be the single best preventative strategy to reduce melanoma risk.

Conjunctival Melanoma in Aotearoa-New Zealand: A 21-Year Analysis of Incidence and Survival

PURPOSE

Conjunctival melanoma (CM) is a rare and aggressive malignancy. Global studies demonstrate increased burden of disease in countries with high rates of cutaneous melanoma. There are currently no reports on CM incidence, trends, or survival within Aotearoa-New Zealand (NZ), a country with the highest global rates of cutaneous melanoma, which this study aims to address.

DESIGN

This was a retrospective review using the national cancer registry.

METHODS

Data on histologically confirmed CM diagnosed between January 1, 2000, and December 31, 2020, were obtained from the NZ Cancer Registry. Cases were identified using the International Classification of Disease, 10th edition (ICD-10) codes. Primary outcome measures were age-standardized incidence, trends, and survival.

RESULTS

A total of 68 CM cases were identified. There was a preponderance for females (n=40, 58.8%) and CM predominantly affected European patients (n=63, 92.6%). Median follow-up was 5.0 years [interquartile range (IQR)=2.4-9.9 y] and the median age at diagnosis was 68.5 years (IQR=57.0-79.0 y), with non-Europeans presenting at a significantly younger age [-17.3 y (95% CI: -31.3 to -3.2), P =0.019] than Europeans. The annual age-adjusted incidence(±SD) was 0.6±0.2 cases per million population per year with a stable incidence trend over 21 years. All-cause mortality was found in 28 cases (41.2%) and the median time to death was 3.76 years (IQR=2.1-5.7 y). Five-year all-cause survival and disease-specific survival was 69% and 90%, respectively.

CONCLUSIONS

This is the first report on CM incidence, trends, and mortality in NZ. The CM burden is in line with European and North American data, despite NZ having the highest rate of cutaneous melanoma. The incidence remained stable over 2 decades.

Ambient UVR and Environmental Arsenic Exposure in Relation to Cutaneous Melanoma in Iowa

Intermittent sun exposure is the major environmental risk factor for cutaneous melanoma (CM). Cumulative sun exposure and other environmental agents, such as environmental arsenic exposure, have not shown consistent associations. Ambient ultraviolet radiation (UVR) was used to measure individual total sun exposure as this is thought to be less prone to misclassification and recall bias. Data were analyzed from 1096 CM cases and 1033 controls in the Iowa Study of Skin Cancer and Its Causes, a population-based, case-control study. Self-reported residential histories were linked to satellite-derived ambient UVR, spatially derived environmental soil arsenic concentration, and drinking water arsenic concentrations. In men and women, ambient UVR during childhood and adolescence was not associated with CM but was positively associated during adulthood. Lifetime ambient UVR was positively associated with CM in men (OR for highest vs. lowest quartile: 6.09, 95% confidence interval (CI) 2.21–16.8), but this association was not as strong among women (OR for highest vs. lowest quartile: 2.15, 95% CI 0.84–5.54). No association was detected for environmental soil or drinking water arsenic concentrations and CM. Our findings suggest that lifetime and adulthood sun exposures may be important risk factors for CM.

Skin cancers in skin types IV-VI: Does the Fitzpatrick scale give a false sense of security?

The Fitzpatrick scale has been in use for skin colour typing according to the tanning potential of skin since its inception in 1975-1976. Thomas Fitzpatrick developed the scale to classify persons with 'white skin' in order to select the correct amount of UVA in Joules/cm² for PUVA treatment for psoriasis. Since then, it has been widely used in Dermatology to gauge the skin's reaction to UV exposure, tanning potential, assessment of sunburn risk and amount of sun protection required for individual patients. However, the use of this scale has been of limited utility because of different self-perception in different areas of the world, particularly among those with skin of colour. Skin cancer risk is loosely inversely correlated with the initial genetic/inherent amount of melanin (most research has focused on eumelanin) present in the skin, although the pattern of exposure and amount of UV radiation required causing DNA damage varies widely according to different cancers. In this review, we have shown that the Fitzpatrick scale is neither correct nor adequate to reflect sunburn and tanning risk for skin of colour. Therefore, it may give both patients and physicians a false sense of security that there is little risk that people of colour can develop skin cancers. We have reviewed the small but not insignificant risk of skin of colour developing skin cancers and emphasise that there remains much research that needs to be done in this field.

Epidemiology of Melanoma in the Czech Republic in East Bohemia in the Period 2002-2017 and the Effect of the Annual Sunshine Exposure

AIM

The evaluation of the trend in the occurrence of melanoma nodulare, melanoma superficiale, lentigo maligna and melanoma in situ in the period of 2002-2017 in East Bohemia region in the Czech Republic. We examine if the annual numbers of hours of sunshine could affect the number of patients with melanoma.

METHOD

In the peridod of 2002-2017, altogether 2230 patients with new diagnosis of melanoma were examined. We studied 1) If there is some trend in the occurrence of lentigo maligna and melanoma in situ, melanoma superficiale, and melanoma nodulare and if there is a difference in the age of patients with this diagnosis (adjusted calculation of specific kind of melanomas and adjusted calculation of age). 2) If the annual numbers of hours of sunshine affect the trend in the occurrence of melanoma and if the annual numbers of hours of sunshine affect the body site of melanoma.

RESULTS AND CONCLUSION

Our study confirmed that the number of patients with lentigo maligna and melanoma in situ had increased in East Bohemia region in the period of 2002-2017. The number of melanomas of nodular and superficial type does not increase. The total number of melanomas in this period does not increase either. No difference of the age of patients with melanoma nodulare, superficiale, lentigo maligna and melanoma in situ was confirmed. We confirmed no relation of the annual numbers of hours of sunshine to the number of melanoma and to the body site of melanoma.

Review of Wearable and Portable Sensors for Monitoring Personal Solar UV Exposure

Sunlight is one of the main environmental resources that keeps all the organisms alive on earth. The ultraviolet (UV) radiation from the sun is essential for vitamin D synthesis in the human body, which is crucial for bone and muscle health. In addition, sun exposure also helps to reduce the risk of some cardiovascular diseases and cancers. However, excessive UV exposure can lead to adverse effects, including some eye diseases, premature aging, sunburn and skin cancers. The solar UV irradiance itself depends on many environmental factors. In fact, the UV index reported in weather forecasts is an estimation under cloudless conditions. Personal UV exposure also depends on one's outdoor activities and habits. Furthermore, the UV intake depends on the skin sensitivity. Therefore, there is a need for research into monitoring the optimal daily UV exposure for health benefits, without developing potential health risks. To facilitate the monitoring of solar UV intensity and cumulative dose, a variety of UV sensors have been developed in the past few decades and many are commercially available. Examples of sensors being marketed are: portable UV dosimeter, wearable UV radiometer, personal UV monitor, and handheld Solarmeter®. Some of the UV sensors can be worn as personal health monitors, which promote solar exposure protection. The paper provides a comprehensive review of the wearable and portable UV sensors for monitoring personal UV exposure, including a discussion of their unique advantages and limitations. Proposals are also presented for possible future research into reliable and practical UV sensors for personal UV exposure monitoring.

Adverse Events of Intense Pulsed Light Combined With Meibomian Gland Expression Versus Meibomian Gland Expression in the Treatment of Meibomian Gland Dysfunction

BACKGROUND AND OBJECTIVE

To analyze the occurrence and causes of adverse events (AEs) in intense pulsed light (IPL) combined with meibomian gland expression (MGX) and MGX treatment alone for meibomian gland dysfunction (MGD).

STUDY DESIGN/MATERIALS AND METHODS

A retrospective study was conducted on MGD patients treated in Wuhan Aier Hankou Eye Hospital from February 2018 to October 2019 to compare the AEs between IPL-MGX and MGX groups. Relevant AEs that occurred during the treatment and within 1 month after the patients' last treatment were recorded and the causes of the AEs were analyzed.

RESULTS

A total of 2,282 patients received IPL-MGX and 1,407 received MGX treatment. No serious AEs occurred in both groups. There were 74 AEs in the IPL-MGX group, with an incidence of 3.24%, including 14 significant AEs (2 cases of epidemic keratoconjunctivitis, 1 recurrent herpes simplex keratitis (HSK), 9 new onsets of floaters, 1 recurrent glaucomatocyclitic crises, and 1 recurrent iridocyclitis). There were 27 AEs in the MGX group with a rate of 1.92%, including 4 significant AEs (2 cases of keratoconjunctivitis epidemic, 2 new cases of floaters). Compared with the IPL-MGX group, the incidence of AEs in the MGX group was lower (P = 0.017).

CONCLUSIONS

Both IPL-MGX and MGX treatment are safe therapies with low risk for AEs. IPL treatment is not recommended for young children (age 10 or less) as well as patients with anterior uveitis or glaucomatocyclitic crises. The previous history of HSK and eyes with high myopia are advised to exercise caution in IPL treatment. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Ultraviolet radiation and cutaneous melanoma: a historical perspective

In this article, we summarize the research that eventually led to the classification of the full ultraviolet (UV) radiation spectrum as carcinogenic to humans. We recall the pioneering works that led to the formulation of novel hypotheses on the reasons underlying the increasing burden of melanoma in light-skinned populations. It took long before having compelling evidence on the association between UV and melanoma, in particular, the importance of UV exposure during childhood for both the occurrence of melanoma and death. The role of UVA was established only after 2005. If molecular lesions caused by UV radiation are better known, the precise mechanism by which UV exposure drives melanoma occurrence and progression still needs to be elucidated. More research on the UV-melanoma relationships has led to more evidence-based sun-protection recommendations, especially for children, and to effective control of the artificial UV tanning fashion. Since around 1985-1995, the mortality because of melanoma has started to decrease in younger age groups in most light-skinned populations. If sun protection among children remain on top of public health agendas, there is a fairly great chance that melanoma mortality will stabilize and steadily decrease in all light-skinned populations. The introduction of effective therapies against metastatic disease will improve this reversal in mortality trends.

Simulation of UV power absorbed by follicular stem cells during sun exposure and possible implications for melanoma development

The incidence of melanoma in children is extremely rare. However, there is convincing evidence supporting a higher risk of developing melanoma in individuals who have experienced excessive sun exposure during their childhood. A possible explanation for this phenomenon is that prior to puberty, the melanocyte stem cells in the bulge region of hair follicles are much shallower in the dermis, resulting in their increased vulnerability to sun exposure. To validate this hypothesis, a Monte Carlo simulation of light transport is applied to quantify the dose of solar UV power absorbed in the stem-cell layers at different depths in both child and adult skins. The simulated results suggest that the stem cells in vellus hair follicles would absorb over 250 times higher UV photons than those in the terminal hair follicles. Due to the thinner epidermis in child skin, the stem cells in vellus hair follicles absorb about 1.9 and 3.2 times greater ultraviolet A and ultraviolet B, respectively, than those in adult skin. These findings provide a possible explanation to why children are particularly vulnerable to sun exposure.

Review of human hair optical properties in possible relation to melanoma development

Immigration and epidemiological studies provide evidence indicating the correlation of high ultraviolet exposure during childhood and increased risks of melanoma in later life. While the explanation of this phenomenon has not been found in the skin, a class of hair has been hypothesized to be involved in this process by transmitting sufficient ultraviolet rays along the hair shaft to possibly cause damage to the stem cells in the hair follicle, ultimately resulting in melanoma in later life. First, the anatomy of hair and its possible contribution to melanoma development, and the tissue optical properties are briefly introduced to provide the necessary background. This paper emphasizes on the review of the experimental studies of the optical properties of human hair, which include the sample preparation, measurement techniques, results, and statistical analysis. The Monte Carlo photon simulation of human hair is next outlined. Finally, current knowledge of the optical studies of hair is discussed in the light of their possible contribution to melanoma development; the necessary future work needed to support this hypothesis is suggested.

Emerging trends in the epidemiology of melanoma

Cutaneous melanoma (CM) is one of the most rapidly growing cancers worldwide, with a consistent increase in incidence among white populations over the past four decades. Despite the early detection of primarily thin melanomas and the improved survival rates observed in several countries, the rate of thick melanomas has remained constant or continues to increase, especially in the older age group. Current considerations in the epidemiology of melanoma focus on the observed survival benefit of females vs. males, the contributing role of indoor tanning in melanoma risk and the diverse effect of sun exposure in the development of different types of melanoma with respect to their clinical and mutational profile. Certain well-known risk factors, such as skin, hair and eye pigmentation and melanocytic naevi have been validated in large-scale association studies, while additional lifestyle factors and iatrogenic exposures, such as immunosuppressive agents and nonsteroidal anti-inflammatory drugs are being investigated. In addition, genome-wide association studies have revealed genetic loci that underlie the genetic susceptibility of melanoma, some of which are related to known risk factors. Recently, an interesting association of melanoma with Parkinson disease has been noted, with a higher than expected frequency of melanoma in patients with Parkinson disease and vice versa. This review article provides an update in the epidemiology of cutaneous melanoma and discusses recent developments in the field.

Country of origin, age at migration and risk of cutaneous melanoma: a migrant cohort study of 1,100,000 Israeli men

Cutaneous melanoma (CM) is a common cancer with increasing incidence in many parts of the world where light-skinned populations live. We conducted a large-scale nationally representative migrant cohort study to assess country of origin and age at migration as predictors of CM, controlling for possible confounders. Data on 1,086,569 Israeli Jewish males, who underwent a general health examination before compulsory military service at ages 16-19 between the years 1967-2005, were linked to Israel National Cancer Registry to obtain incident CM up to 2006. Cox proportional hazards was used to model time to event. Overall, 1562 incident cases were detected during 19.3 million person-years of follow-up. Origin was a strong independent predictor of CM. Incidence was higher for European (hazard ratio [HR] = 4.08, 95% confidence interval [CI]: 3.55-4.67) and Israeli origin (HR = 2.92, 95% CI: 2.25-3.79) compared to N. African/Asian origin, adjusted for year of birth, years of education, residential socio-economic position, rural residence and body surface area (or height). Among those of European origin, the adjusted risk was significantly lower for those who immigrated after the age of 10 years (HR = 0.58, 95% CI: 0.45-0.73) but not for younger ages (HR = 1.02, 95% CI 0.84-1.23) compared to Israeli born. The high rates of CM among men of European origin and the almost twofold lower risk among those immigrating after age 10 provide solid support for the deleterious role of childhood sun exposure as a risk factor for melanoma. These findings will serve in directing public health and research efforts.

Quantification of ultraviolet radiation-induced DNA damage in the urine of Swedish adults and children following exposure to sunlight

CONTEXT

DNA damage following exposure to ultraviolet radiation (UVR) is important in skin cancer development. The predominant photoproduct, cyclobutane thymine dimer (T=T), is repaired and excreted in the urine, where it provides a biomarker of exposure.

OBJECTIVE

To quantify urinary T=T levels after recreational sunlight exposure in adults and children.

METHODS

Average UVR doses were measured with personal dosimeters. Urinary T=T was analysed with (32)P-postlabelling.

RESULTS

Background levels of T=T increased significantly following exposure to sunlight. Amounts of T=T in urine of children and adults were not significantly different after adjusting for area of skin exposed and physiological differences. UVR dose and amounts of T=T correlated for both adults and children.

CONCLUSION

Recreational exposure to sunlight in Sweden induces levels of DNA damage, clearly detectable in urine.

Ultraviolet radiation and melanoma

Melanoma is a particularly aggressive type of skin cancer, and its incidence has been increasing steadily since the 1970s. This article will review the extensive epidemiologic data demonstrating that ultraviolet radiation (UVR) exposure, from the sun or artificial tanning beds, is the most important environmental risk factor for melanoma; the multiple detrimental effects of UVR on human skin, including DNA damage through the formation of dimeric photoproducts, gene mutations, oxidative stress, inflammation, and immunosuppression, all of which contribute to melanomagenesis; and the evidence that protection from UVR exposure, whether by melanin or by sunscreen, reduces the risk of developing melanoma.

Malignant melanomas on head/neck and foot: differences in time and latitudinal trends in Norway

BACKGROUND

Cutaneous malignant melanoma (CMM) incidence continues to increase in many parts of the world. Solar ultraviolet (UV) radiation is the main environmental risk factor for CMM. Different body locations are subjected to different doses and exposure patterns of solar UV. Time and latitudinal trends of CMMs on shielded and exposed skin give valuable information about the aetiology of these cancers. In this study, we have compared the time and latitudinal trends of CMM incidence on skin areas which are chronically (head and neck) and rarely (foot) exposed to UV radiation, to gain more information about the relationship between sun doses, exposure patterns and melanomagenesis.

METHODS

We have analysed epidemiological data from the Cancer Registry of Norway, for foot and head and neck CMM for two time periods: 1966-1986 and 1987-2007.

RESULTS

Cutaneous malignant melanoma incidence rate on head and neck has increased with time, while incidence rates of foot CMM have remained almost constant with time in Norway. There is a large north-south gradient in incidence rates of CMM on head and neck in Norway, while there is almost no north-south gradient for CMM incidence on foot.

CONCLUSIONS

Comparisons of time trends and latitudinal trends of the incidence rates of CMM on head/neck and on foot indicate that solar radiation plays a role in the induction of the former CMM but probably not for the latter.

Solar UVR Exposure, Concurrent Activities and Sun-Protective Practices Among Primary Schoolchildren

Comprehensive measures of ultraviolet radiation (UVR) exposure, concurrent activities and sun-protective practices are needed to develop and evaluate skin cancer prevention and sun protection interventions. The UVR exposures of 345 primary schoolchildren at 23 schools around New Zealand were measured using electronic UVR monitors for 1-week periods over 12 weeks in 2004 and 2005. In addition, ambient UVR levels on a horizontal surface were measured on-site at each school. Children completed activity diaries during the period UVR measurements were made and provided information on their indoor and outdoor status and clothing and sun protection worn. Mean total daily UVR exposure (7:00-20:00 h NZST + 1) at the body location where the UVR monitors were worn was 0.9 SED (standard erythemal dose, 1 SED = 100 J m(-2)). This was 4.9% of the ambient UVR on a horizontal surface. Mean time spent outdoors was 2.3 h day(-1). Differences in children's UVR exposure could be explained in part by activity, where outdoor passive pursuits were associated with higher UVR exposure rates than outdoor active and outdoor travel pursuits. Compared with older children, the activities of younger children, although labeled the same, resulted in different UVR exposures, either as a result of reporting differences or a real difference in UVR exposure patterns. UVR exposure rates were generally higher on weekdays compared with the weekend, confirming the important role of school sun protection and skin cancer prevention programs. High UVR exposure activities included physical education, athletics and lunch break.

Cutaneous malignant melanoma in children and adolescents in Sweden, 1993–2002: The increasing trend is broken

The incidence of cutaneous malignant melanoma rose rapidly in teenagers in Sweden during 1973-1992, while it remained low in younger children. To study the further trends and characteristics of melanoma in this young population, data on all cases in individuals under 20 years of age reported to the Swedish Cancer Registry during 1993-2002, and the corresponding pathology reports were examined. Seventy-nine cases were reported to the Registry. There were 24 males and 55 females. Most melanomas occurred on the trunk followed by the legs in both genders. The median tumor thickness was 0.8 mm. Children under age 15 had thicker melanomas than individuals aged 15-19. Superficial spreading melanoma was the most common histological subtype (43/78, 55%). The melanoma-specific 5-year survival rate was 90%. During 1993-2002, the age-standardized incidence fell to 3.6/million from 5.0/million in 1983-1992 (RR 0.74, 95% CI 0.58-0.92). The most pronounced decrease was for melanomas on the trunk in boys and on the legs in girls. The incidence for 15-19-year-old boys peaked for the cohort born between 1968 and 1972 and for girls between 1973 and 1977. The decrease in incidence may be a result of public health campaigns aiming at reducing sun exposure in childhood. A contributing effect from an increased immigration of individuals with darker complexions and at a lower melanoma risk is probable.

Risk factors for skin cancers: a nested case–control study within the Nurses’ Health Study

BACKGROUND

Constitutional factors and sun exposure are associated with skin cancer risk. However, these relations are complex and differ according to skin cancer type.

METHODS

We examined the associations of constitutional risk factors and sun exposure with the risks of three types of skin cancer simultaneously and evaluated the interaction between constitutional susceptibility and sun exposure in a nested case-control study within the Nurses' Health Study [200 melanoma, 275 squamous cell carcinoma (SCC), and 283 basal cell carcinoma (BCC) cases, and 804 controls]. Information regarding skin cancer risk factors was obtained from the retrospective supplementary questionnaire.

RESULTS

Constitutional susceptibility was an independent risk factor for all three types of skin cancer. Sunlamp usage or tanning salon attendance was a risk factor for melanoma after adjusting for potential confounding variables (OR for ever vs never usage, 2.06, 95% CI 1.30-3.26). Higher sun exposure while wearing a bathing suit was an independent risk factor for all three types of skin cancer. We observed a significant interaction between constitutional susceptibility and sun exposure while wearing a bathing suit on melanoma risk (P, interaction, 0.03); women with the highest susceptibility and highest exposure had an OR of 8.37 (95% CI 3.07-22.84). This interaction was weaker and non-significant for SCC and BCC.

CONCLUSIONS

These data largely confirm past studies on risk factors for skin cancer but provide evidence of difference on the strength of these risk factors for melanoma compared with SCC and BCC.

Sun exposure and risk of melanoma

BACKGROUND

As skin cancer education programmes directed to children and adolescents continue to expand, an epidemiological basis for these programmes is necessary to target efforts and plan for further evaluation.

AIMS

To summarise the epidemiological evidence on sun exposure during childhood and adolescence and melanoma risk.

METHODS

A literature review was conducted using Medline (1966 to December 2004) to identify articles relating to sun exposure and melanoma. The review was restricted to studies that included sun exposure information on subjects 18 years of age or younger.

RESULTS

Migrant studies generally indicate an increased melanoma risk in individuals who spent childhood in sunny geographical locations, and decreasing melanoma risk with older age at arrival. Individuals who resided in geographical locations close to the equator or close to the coast during childhood and/or adolescence have an increased melanoma risk compared to those who lived at higher latitudes or never lived near the coast. The intermittent exposure hypothesis remains controversial; some studies indicate that children and adolescents who received intermittent sun exposure during vacation, recreation, or occupation are at increased melanoma risk as adults, but more recent studies suggest intermittent exposure to have a protective effect. The majority of sunburn studies suggest a positive association between early age sunburn and subsequent risk of melanoma.

CONCLUSION

Future research efforts should focus on: (1) clarifying the relation between sun exposure and melanoma; (2) conducting prospective studies; (3) assessing sun exposure during different time periods of life using a reliable and quantitative method; (4) obtaining information on protective measures; and (5) examining the interrelations between ability to tan, propensity to burn, skin type, history of sunburns, timing and pattern of sun exposure, number of nevi, and other host factors in the child and adolescent populations.

Neonatal susceptibility to UV induced cutaneous malignant melanoma in a mouse model

UV irradiation has multiple effects on skin including erythema, immunosuppression and the induction of keratinocyte-derived skin cancers and cutaneous malignant melanoma (CMM). CMM which arises from damage to the melanocyte, the pigment cell of the skin, is associated in epidemiologic studies with sun-exposure of susceptible populations, especially children. Our experimental studies have supported the concept that the epidemiologically observed susceptibility in children has a biologic basis. Hepatocyte growth factor/scatter factor (HGF/SF) transgenic mice neonatally irradiated with UV produce melanomas which recapitulate human disease in histopathology and molecular pathogenesis. In this model, neonatal UV is necessary and sufficient for melanoma induction although an additional adult dose of UV radiation significantly increased melanoma multiplicity. One hypothesis for the susceptibility of neonatal mice to induction of melanoma is that neonatal skin contains a large number of immature melanocytes which may result in the retention of the consequences of UV damage throughout the lifetime of the animal. An alternate hypothesis is that the immaturity of the neonatal immune system results in tolerance to melanocytic antigens produced by UV exposure, thus permitting the subsequent outgrowth of melanoma. Here, we discuss the current state of knowledge about the differences between adult and neonatal mice in melanocytes and immune maturation as possible factors playing a role in the susceptibility to melanoma in UV irradiated HGF/SF transgenic mice.

Melanoma and lifetime UV radiation

OBJECTIVE

Because most risk factors for melanoma are immutable constitutional factors such as skin type, it is important to more fully understand the relationship between melanoma risk and sun exposure, one of the few modifiable risk factors for the disease. The goal of this case-control study was to quantify the risks of melanoma associated with UV exposure at different periods of life.

METHODS

Cases were 386 patients between the ages of 35 and 74 who were diagnosed with primary cutaneous melanoma within the Seattle-Puget Sound area during 1997. Controls were 727 participants of the same age and geographic area, selected by random-digit dialing. A telephone interview included a complete residential history, lifetime sun exposure history (days in the summer sun for at least 4 h at each place of residence), and personal characteristics. UV exposure was calculated based on satellite data on potential erythemal exposure at each place of residence, years at each location and time spent in the sun at each location. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) reflecting the risk of melanoma associated with UV exposure, after adjustment for age, sex, income, tendency to burn and sunburns during ages 2-10.

RESULTS

Among women, lifetime UV exposure was associated with melanoma risk (adjusted OR = 1.99 for highest versus lowest quartile, 95% CI: 0.95-3.03, p for trend = 0.008). There were significant trends for UV exposure during ages 1-10, 11-20 and 31-40 (all p < 0.02). Among men, there were no significant associations at any time period, but lifetime UV exposure was associated with higher risk for men who had a tendency toward severe or painful sunburns (OR = 2.85 for highest versus lowest quartile, 95% CI: 0.84-9.64, p for trend = 0.04).

CONCLUSION

The differing results by sex are not easily interpretable, though it may be useful to target those with a higher sensitivity to the sun when formulating messages for prevention of melanoma by lowering exposure to UV.

Bronzeamento e risco de melanoma cutâneo: revisão da literatura

Estudos epidemiológicos sugerem a relação entre comportamentos relacionados ao bronzeamento e risco elevado de melanoma. Nesse sentido, realizou-se revisão sobre essa temática que abrangeu o período correspondente aos anos de 1977 a 1998. Foram pesquisadas as bases de dados Medline e Embase (Excerpta Medica). A análise mostrou que entre os jovens, apesar do conhecimento sobre os riscos da exposição excessiva à radiação ultravioleta e sobre as práticas visando à proteção da pele, prevalece o hábito de expor-se intencionalmente ao sol. Esse hábito é alimentado por crenças e atitudes em relação ao bronzeado e estimulado por influência do grupo e de pessoas consideradas "referências". As práticas mais freqüentemente adotadas para bronzear a pele apresentam risco elevado para o desenvolvimento de melanoma. Conclui-se que a forma mais eficaz de prevenir o melanoma é divulgar nos meios de comunicação que a pele bronzeada não é saudável, pois foi danificada pela radiação ultravioleta solar; e iniciar campanhas com ações efetivas para mudar comportamentos, naquilo que os motiva e os alimenta.

Epidemiology of malignant melanoma

Trends in melanoma incidence have shown an increase in thinner, less lethal tumors in recent years. The overall increases in melanoma incidence have begun to slow in Western Europe and North America. Environmental risk factors are important in the development of melanomas in individuals with high-risk phenotypes, and these people should modify their recreational and overall UV exposure. Primary prevention of melanoma and early detection are essential to reduce melanoma mortality in future years. The complex relationships between genetic factors and patterns of sun exposure, especially in childhood, are the focus of continued research.

Skin cancer prevention counseling and clinical practices of pediatricians

Little is known about pediatricians' counseling and clinical practices to reduce skin cancer risk among their patients. Thus our objectives were to characterize skin cancer preventive counseling and clinical practices in a sample of pediatricians and identify correlates of these practices. Physicians practicing general pediatrics in Harris County, Texas, received a mail survey that assessed their sun protection recommendations and skin cancer preventive counseling and clinical practices. Pediatrician, patient, and medical practice variables were assessed as correlates. Most (76%) pediatricians routinely recommended sunscreen; however, relatively few (24%) suggested reapplying it after prolonged periods outside. About half routinely recommended protective clothing (53%), shade (47%), or limiting midday sun exposure (46%). Even fewer pediatricians routinely discussed skin cancer risk factors, passed out sunscreen samples, made educational materials available, took a family history of skin cancer, or documented risk factors in a patient's chart. More than half reported that they routinely performed full-body skin examinations during a first visit (65%) and annually (56%). Perceived barriers, perceived relevance of skin cancer prevention, and personal sun protection practices were important factors associated with professional practices in this sample. Interventions are needed to increase pediatricians' counseling and clinical practices to reduce skin cancer risk among patients.

Teen smoking, field cancerization, and a "critical period" hypothesis for lung cancer susceptibility

Cigarette smoking by children and adolescents continues to be prevalent, and this fact represents a major public health problem and challenge. Epidemiologic work has previously suggested that exposure of the lung to tobacco carcinogens at an early age may be an independent risk factor for lung cancer. Recent studies at the molecular and cellular levels are consistent with this, now suggesting that early exposure enhances DNA damage and is associated with the induction of DNA alterations in specific chromosomal regions. In this paper we hypothesize that adolescence, which is known to be the period of greatest development for the lung, may constitute a "critical period" in which tobacco carcinogens can induce fields of genetic alterations that make the early smoker more susceptible to the damaging effects of continued smoking. The fact that lung development differs by sex might also contribute to apparent gender differences in lung cancer susceptibility. Because this hypothesis has important implications for health policy and tobacco control, additional resources need to be devoted to its further evaluation. Targeted intervention in adolescent smoking may yield even greater reductions in lung cancer occurrence than otherwise anticipated.

In vitro transformation of human congenital naevus to malignant melanoma

The incidence of melanoma is estimated to be growing at the second fastest rate among all cancers in the United States. The progression of the melanocyte to a malignant melanoma involves various sequential steps: development of benign naevocellular naevus, preneoplastic dysplastic naevus, primary melanoma, and metastatic melanoma. Despite these clearly defined stages, very little is known about the molecular events leading to melanoma progression. We established a human congenital naevus cell line (UISO-CMN-1). UISO-CMN-1 cells were confirmed to have melanocytic origin by S100 immunoreactivity and the presence of melanin granules and melanosomes. UISO-CMN-1 cells, even though they showed structural and numerical abnormalities in karyotype, were non-tumorigenic when transplanted into athymic mice. However, following frequent exposure to ultraviolet C radiation, UISO-CMN-1 cells acquired tumorigenic potential. Transformation of UISO-CMN-1 cells into tumorigenic cells was accompanied by induction of ganglioside-2 expression without any significant changes in cellular ganglioside-3. These transformed and non-transformed UISO-CMN-1 cell lines can serve as excellent research tools for studying the molecular changes associated with melanoma development and progression, and for identifying agents that might prevent development of malignant melanoma.

The body site distribution of melanocytic naevi in 6-7 year old European children

The number and size of melanocytic naevi are the main predictors of cutaneous melanoma. Naevus development per unit of skin surface is greatest during childhood. We assessed the body distribution of naevi 2-4.9 mm and > or = 5 mm in 649 European children aged 6-7 years old from Brussels (Belgium), Bochum (Germany), Lyon (France) and Rome (Italy). The numbers of naevi 2-4.9 mm and naevi > or = 5 mm were strongly correlated, especially on the trunk. For naevi 2-4.9 mm, the highest relative densities were found on the face, back, shoulders and the external surface of the arms. The lowest relative densities were found on the hands, legs, feet and abdomen. The relative density of naevi > or = 5 mm was higher on the trunk than on any other body site. Similar body distributions were observed in both sexes and at each centre. The body site distribution of naevi 2-4.9 mm seemed to parallel the usual sun exposure patterns of young European children. It is suggested that the development of naevi > or = 5 mm might be a marker of the vulnerability of melanocytes to the harmful effects of solar radiation. Vulnerability would be maximal on the back, and would decrease from proximal to distal skin areas, with melanocytes of the hands and feet having the lowest vulnerability. The number of naevi acquired on a specific area of skin would result from the combined effects of local vulnerability to solar radiation and local sun exposure history. The origin of acquired body site differences in the susceptibility of melanocytes to ultraviolet radiation is unknown, although it seems to parallel the body site density of sensory innervation.

Sun Protection is Fun! A skin cancer prevention program for preschools

Children and their caregivers are prime candidates for intervention to curb the rising incidence of skin cancer in the United States. Preschools provide a unique opportunity to influence the sun protection practices of parents and teachers on behalf of young children. Sun Protection is Fun!, a comprehensive skin cancer prevention program developed by The University of Texas M. D. Anderson Cancer Center in collaboration with The University of Texas-Houston Health Science Center School of Public Health, was introduced to preschools in the greater Houston area. The program's intervention methods are grounded in Social Cognitive Theory and emphasize symbolic modeling, vicarious learning, enactive mastery experiences, and persuasion. Program components include a curriculum and teacher's guide, videos, newsletters, handbooks, staff development, group meetings designed to encourage schoolwide changes to support the program, and sunscreen. The intervention map, including objectives for program development, implementation, and evaluation, is discussed.

A comparison of melanoma mortality among WWII veterans of the Pacific and European theaters

PURPOSE

To determine whether cutaneous melanoma is associated with past military service in tropical locations, as a test of the 'critical period' sunlight exposure hypothesis.

METHODS

Mortality data from a longitudinal follow-up study of 5524 former prisoners of war (POW) and 3713 non-POW veteran controls, all white male veterans of World War II (WWII), were examined to determine whether death attributed to melanoma was associated with history of military service in Pacific or European theaters during WWII or with POW status. Deaths from colon cancer were used as a comparison outcome.

RESULTS

During 50 years of follow-up, there were 18 deaths from melanoma and 83 deaths from colon cancer among the cohort. Melanoma mortality varied with theater of war and POW status, whereas colon cancer mortality was similar for all subgroups. Pacific War POWs were at the highest risk overall (odds ratio (OR), 3.35; 95% confidence interval (CI), 0.39-28.76), whereas veterans of the Pacific War had nearly the same risk of melanoma (OR, 1.04; 95% CI, 0.09-11.94) compared with veterans of the European War. European theater POWs had a higher risk than non-POW veterans (OR, 2.76; 95% CI, 0.31-24.81). None of these differences, however, were statistically significant.

CONCLUSIONS

To the extent that POW status is associated with higher sun exposure, these data are consistent with the hypothesis that exposure to high levels of solar radiation in young adulthood is associated with a higher risk of melanoma mortality.

The genetics of hereditary melanoma and nevi. 1998 update

Although the first English-language report of melanoma in 1820 contained a description of a melanoma-prone family, it was 1983 before formal genetic analysis suggested an autosomal dominant mode of inheritance for both melanoma and the then newly described melanoma precursor, dysplastic nevi (DN). Subsequent genetic studies have assumed this model to be correct, although when viewed in aggregate, the data are inconsistent. The first proposed melanoma gene (CMM1) was mapped to chromosome 1p36. This gene assignment has not been confirmed. A second melanoma gene, designated CMM2, has been mapped to chromosome 9p21. This gene assignment has been confirmed, and the cell cycle regulator CDKN2A has been proposed as the candidate gene. Germline mutations in this gene have been identified in about 20% of melanoma-prone families that have been studied to date. Pancreatic cancer occurs excessively in melanoma families with germline mutations in CDKN2A. Germline mutations in the cyclin-dependent kinase gene CDK4 (chromosome 12q14) have been described in three melanoma families. This finding represents a third melanoma gene but one that accounts for only a tiny fraction of all hereditary melanoma. Recently, a familial melanoma-astrocytoma syndrome has been reported. Large germline deletions of 9p21 occur in these families, with the p19 gene implicated in its pathogenesis. At present, clinical predictive genetic testing for mutations in the CDKN2A gene is available commercially, but its use has been limited by uncertainty as to how test results would affect the management of melanoma-prone family members. Currently, management recommendations include monthly skin self-examination, clinical skin examination once or twice yearly, a low threshold for simple excision of changing pigmented lesions, moderation of sun exposure, and appropriate use of sunscreens. A heritable determinant for total nevus number has been suggested by twin studies. Other data suggest the presence of a major gene responsible for "total nevus density" in melanoma-prone families. Approximately 55% of the mole phenotype in multiplex melanoma families was explained by this proposed gene. An autosomal dominant mode of inheritance has been proposed for DN, and data exist to suggest that DN may be a pleiotropic manifestation of the 1p36 familial melanoma gene. However, there clearly are melanoma-prone families that do not express the dysplastic nevus trait, and some of the families linked to CDKN2A also present with dysplastic nevi. Several studies have shown a surprisingly high prevalence of DN on the skin of family members of probands with DN. In light of the extensive evidence documenting that persons with DN (both sporadic and familial) have an increased prospective risk of melanoma, these family studies suggest that relatives of persons with DN should be examined for both DN and melanoma. Genetic determinants play a major role in the pathogenesis of normal nevi, DN, and melanoma. Identifying the molecular basis of these genetic events promises to enhance melanoma risk-reduction strategies and, ultimately, reduce melanoma-associated mortality.

Influence of sun exposures during childhood and during adulthood on melanoma risk. EPIMEL and EORTC Melanoma Cooperative Group. European Organisation for Research and Treatment of Cancer

Sun exposure in both childhood and adult life represents the main environmental risk determinant for cutaneous melanoma. However, little is known about the joint effects of sun exposure during early and later life on melanoma risk. A case-control study in Belgium, Germany and France conducted in 1991-1992 suggests that the melanoma risks attached to indicators related to sun exposure appear to combine their effects in an additive way. We therefore constructed composite indices of sun exposure during childhood and during adulthood, assuming additive combinations of melanoma risk associated with each indicator of sun exposure. Logistic regression modeling showed that the melanoma risk associated with a given level of sun exposure during adulthood increased with higher sun exposure during childhood, but the increase in risk was higher than the simple addition of melanoma risk associated with sun exposure during childhood or adulthood. In turn, high sun exposure during childhood constituted a significant risk factor for melanoma only if there was substantial sun exposure during adult life. We thus suggest that sun exposure during childhood and during adulthood would be interdependent as far as their impact on melanoma risk is concerned. Our results support the hypothesis by which the important contribution of sun exposure during childhood in melanoma occurrence is not properly assessed by retrospective epidemiologic studies. Sun avoidance during childhood would have a greater impact on melanoma risk than sun avoidance during adulthood.