Melanoma and exposure to sunlight

REPRINT OF: Racism, Sexism, and Social Class: Implications for Studies of Health, Disease, and Well-being

Editor's Note: This article is a reprint of a previously published article. For citation purposes, please use the original publication details: Krieger N, Rowley DL, Herman AA, Avery B, Phillips MT. Racism, sexism, and social class: implications for studies of health, disease, and well-being. Am J Prev Med. 1993;9(6 suppl):82-122.

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.

The circadian control of skin and cutaneous photodamage

Biologically, light including ultraviolet (UV) radiation is vital for life. However, UV exposure does not come without risk, as it is a major factor in the development of skin cancer. Natural protections against UV damage may have been affected by lifestyle changes over the past century, including changes in our sun exposure due to working environments, and the use of sunscreens. In addition, extended "day time" through the use of artificial light may contribute to the disruption of our circadian rhythms; the daily cycles of changes in critical bio-factors including gene expression. Circadian disruption has been implicated in many health conditions, including cardiovascular, metabolic and psychiatric diseases, as well as many cancers. Interestingly, the pineal hormone melatonin plays a role in both circadian regulation as well as protection from UV skin damage, and is therefore an important factor to consider when studying the impact of UV light. This review discusses the beneficial and deleterious effects of solar exposure, including UV skin damage, Vitamin D production, circadian rhythm disruption and the impact of melatonin. Understanding these benefits and risks is critical for the development of protective strategies against solar radiation.

Time trends and latitude dependence of uveal and cutaneous malignant melanoma induced by solar radiation

In order to evaluate the role of solar radiation in uveal melanoma etiology, the time and latitude dependency of the incidence rates of this melanoma type were studied in comparison with those of cutaneous malignant melanoma (CMM). Norway and several other countries with Caucasian populations were included. there is a marked north-south gradient of the incidence rates of CMM in Norway, with three times higher rates in the south than in the north. No such gradient is found for uveal melanoma. Similar findings have been published for CMM in other Caucasian populations, with the exception of Europe as a whole. In most populations the ratios of uveal melanoma incidence rates to those of CMM tend to decrease with increasing CMM rates. This is also true for Europe, in spite of the fact that in this region there is an inverse latitude gradient of CMM, with higher rates in the north than in the south.In Norway the incidence rates of CMM have increased until about 1990 but have been constant or even decreased (for young people) after that time, indicating constant or decreasing sun exposure. The uveal melanoma rates have been increasing after 1990. In most other populations the incidence rates of CMM have been increasing until recently while those of uveal melanoma have been decreasing. These data generally support the assumption that uveal melanomas are not generated by ultraviolet (UV) radiation and that solar UV, via its role in vitamin D photosynthesis, may have a protective effect.

High incidence of second basal cell skin cancers

We considered the risk of second basal cell cancers (BCC) of the skin using a population-based series of 1,868 BCC collected between 1976 and 1985 in the Swiss Cantons of Vaud and Neuchâtel, and followed-up to the end of 2003. Overall, 507 second BCC were observed versus 59.98 expected, corresponding to a standardized incidence ratio (SIR) of 8.45 (95% CI: 7.73-9.22). The SIRs were similar in men and women in subsequent calendar periods, but tended to decline with advancing age at diagnosis of first BCC, from 13.98 below age 50 to 7.13 at age 70 or over. Consequently, the rate of first BCC increased to approximately 30-fold between 7/100,000 at age 30-39 and 200/100,000 at age 70-79, but the rate of second BCC increased only about 3-fold between 31/1,000 at age 30-39 and 110/1,000 at age 70-79. The cumulative risk of second BCC was 11% at 5 years, 21% at 10 years and 40% at 20 years. This study indicates that the relative (but not the absolute) risk of second BCC is greater at younger age and declines with advancing age, and is therefore compatible with an excess baseline risk in a population of susceptible individuals.

Epidemiologic evidence for different roles of ultraviolet A and B radiation in melanoma mortality rates

PURPOSE

The action spectrum of ultraviolet radiation mainly responsible for melanoma induction is unknown, but evidence suggests it could be ultraviolet A (UVA), which has a different geographic distribution than ultraviolet B (UVB). This study assessed whether melanoma mortality rates are more closely related to the global distribution of UVA or UVB.

METHODS

UVA and UVB radiation and age-adjusted melanoma mortality rates were obtained for all 45 countries reporting cancer data to the World Health Organization. Stratospheric ozone data were obtained from NASA satellites. Average population skin pigmentation was obtained from skin reflectometry measurements.

RESULTS

Paradoxically, melanoma mortality rates decreased with increasing UVB in men (r = -0.48, p < 0.001), and women (r = -0.57, p < 0.001), and with increasing UVA in both sexes. By contrast, rates were positively associated with increasing UVA/UVB ratio in men (r = + 0.49, p < 0.001) and women (r = + 0.55, p < 0.001). After multiple adjustment that included controlling for skin pigmentation, only UVA was associated with melanoma mortality rates in men (p < 0.02) with a suggestive but non-significant trend present in women (p = 0.12).

CONCLUSIONS

UVA radiation was associated with melanoma mortality rates after controlling for UVB and average pigmentation. The results require confirmation in observational studies.

[Primary malignant melanoma of the uterine cervix. Report of two cases and review of the literature]

The manifestation of a malignant melanoma in the uterus is very rare, more often it is the result of metastasis rather than a primary tumor. A malignant melanoma at this site can originate either from melanocytic elements within the cervical epithelium or from the cervical stroma. We report on two cases of primary malignant melanoma of the uterine cervix and compare them with other cases from the literature.

Moderate sun exposure and nevus counts in parents are associated with development of melanocytic nevi in childhood: a risk factor study in 1,812 kindergarten children

BACKGROUND

Melanocytic nevi have been identified as the most important risk factor for cutaneous melanoma. Sun exposure, sunburns, and light pigmentation have been found to be associated with their development in childhood. To the authors' knowledge, nevus proneness of parents and the exact type of ultraviolet (UV) exposure have not yet been investigated in this context. The authors' objective was to determine independent risk factors and their impact for nevus development in childhood.

METHODS

The current study was conducted by two university departments of dermatology in 49 public nursery schools in Stuttgart, Germany and in 38 public nursery schools in Bochum, Germany. The cross-sectional study included 1,812 children aged 2-7 years and their parents. Total body nevus counts in children, assessment of pigmentary features, and nevus counts on the arms of parents were performed. Parents underwent a standardized interview concerning national origin and lifestyle features, as well as habits and magnitude of sun exposure of children. Analysis was performed by multivariate linear regression analysis and by multiple logistic regression analysis.

RESULTS

The number of nevi was found to steadily increase with age from a median of 3 at age 2 years to 19 at age 7 years (P < 0.0001). High numbers of nevi in children were associated with the number of weeks on sunny holidays, outdoor activities at home, skin type, facial freckling, ethnicity of parents, and the number of nevi on the arms of parents. Previously experienced sunburns failed significance (P = 0.0620).

CONCLUSIONS

The authors found a strong association between nevus development in children and the number of parental moles, which most likely points to an inherited factor. Moderate sun exposure such as outdoor activities during a German summer without sunburns seemed to be sufficient for induction of melanocytic nevi. The authors believe that these findings will have direct impact on concepts for preventive strategies.

Gender differences in rising trends in cutaneous malignant melanoma in Spain, 1975-98

BACKGROUND

Cutaneous malignant melanoma (CMM) morbidity and mortality rates have increased over the past several decades all around the world, but some developed countries have experienced recent declines in mortality from CMM among the young and middle-aged and even a reversal in the long-term increase in deaths attributable to CMM.

OBJECTIVES

To describe CMM mortality trends, by age and gender, in Spain between 1975 and 1998.

METHODS

Crude, age-adjusted, truncated, cumulative, age-specific and potential years of life lost rates of CMM mortality were calculated by gender. Age and period Poisson regression models were fitted to gender- and age-specific CMM mortality rates.

RESULTS

In males there were marked increases in all CMM mortality rates between 1975 and 1994, followed by their decrease during 1995-98. In contrast, rates rose in females between 1975 and 1998. There were annual increases of 13% in the risk of dying among males and 33% among females. Relative risks of CMM mortality increased with age in both genders: (i) 21.75 (95% confidence interval, CI 17.32-27.30) in males, and (ii) 28.27 (95% CI 24.99-31.97) in females in the > or = 70-year-old group, when compared with those < 35 years.

CONCLUSIONS

CMM mortality rates continue to rise in females while males have experienced a recent reversal of this trend in Spain. Emphasizing the danger of overexposure to ultraviolet radiation may be especially important in females.

Occupational sunlight exposure and cancer incidence among Swedish construction workers

We studied sunlight exposure from outdoor work in relation to cancer, using data from 323,860 men participating in an occupational health service program of the Swedish construction industry. An experienced industrial hygienist assessed the exposure for 200 job tasks. We estimated relative risks (RRs) adjusted for age, smoking, and magnetic field exposure. There was an increased RR in the high-exposure group for myeloid leukemia [RR = 2.0, 95% confidence interval (95% CI) = 1.1-3.6] and lymphocytic leukemia (RR = 1.7, 95% CI = 0.9-3.2). For non-Hodgkin's lymphoma there was a 30% increase in risk in the high-exposure group (95% CI = 0.9-1.9). There was no increased risk of malignant melanoma, except for tumors of the head, face, and neck in the high-exposure group (RR = 2.0, 95% CI = 0.8-5.2), and we also found an increased risk for malignant melanoma of the eye in this group (RR = 3.4, 95% CI = 1.1-10.5). Outdoor workers had no increased risk of nonmelanoma skin cancer. Nevertheless, the RR for lip cancer (squamous cell carcinoma) among the high-exposure group was estimated at 1.8 (95% CI = 0.8-3.7). Among other sites, an increased risk of stomach cancer was suggested in this group (RR = 1.4, 95% CI = 1.0-1.9). The results for lymphoma, leukemia, and possibly also for stomach cancer might reflect a suppression of the immune system from ultraviolet light in outdoor workers.

Site-specific risk of cutaneous malignant melanoma and pattern of sun exposure in New Zealand

The site-specific relationship between melanoma and sun exposure was investigated in the high-risk region of New Zealand. Age and latitude of residence were used as biological and geographical proxy measures of exposure for the 16,117 newly incident cases and 3,150 death records reported between 1968 and 1993. Age-standardized rates were the highest for the trunk in males and for the lower limbs in females, but once body surface area was accounted for, highest rates were found on fully exposed sites, particularly the ears in men. Melanomas occurred at a substantially younger age on intermittently exposed sites than chronically exposed ones (difference of about 13 and 27 years for men and women, respectively, between the trunk and the face). Age and latitude were found to influence melanoma rates in a sex- and site-specific fashion. For heavily exposed body areas, incidence rates increased more modestly with age before age 50 than after. In contrast, sharp increases in risk occurred from early age for episodically exposed sites with a reversal of trend observed among the elderly. For males, the magnitude of the latitude gradient was about 65% (incidence) and 50% (mortality) greater for body areas most intermittently exposed compared with those with a least intermittent pattern of exposure. The latitude gradient was steeper for males than females and for incidence than mortality, regardless of the pattern of site exposure. Sex- and age-specific differences in risk were largely explained by the varying patterns of exposure. These results confirm that intermittent exposure is probably more effective than continuous exposure in producing an early onset of melanoma. Reducing the episodes of acute exposure remains a paramount aspect to melanoma prevention strategies.

Extrafacial lentigo maligna melanoma: analysis of 71 cases and comparison with lentigo maligna melanoma of the head and neck

We report a retrospective analysis of extrafacial lentigo maligna melanoma (LMM), and a comparison with patients with LMM of the head and neck. Seventy-one patients (22 men, 49 women) with extrafacial LMM were identified from the Scottish Melanoma Group database for January 1979-March 1996. Their mean age (63 years) was significantly less than that of 335 patients with head and neck LMM (mean 72 years, P < 0.001), with a significantly greater difference among women than men. Extrafacial sites comprised 17.5% of LMMs. There was a marked body site distribution difference between the sexes (P = 0. 001): 68% of extrafacial LMMs in men were on the trunk while 80% in women were on the limbs, particularly the lower leg. Extrafacial LMMs were thinner at presentation than head and neck LMMs (P < 0.05) in both sexes, but this was not simply explained by the younger age of these patients as there was no significant correlation between age and tumour thickness at either extrafacial or at head and neck sites. Although the female lower leg is a site of chronic solar exposure in older women, the other extrafacial sites are habitually covered in the temperate Scottish climate. The significantly younger age group of patients with LMM at extrafacial compared with head and neck sites therefore suggests that the relationship between LMM and sunlight is not simply related to cumulative solar exposure. The demonstration that head and neck LMMs were thicker at presentation compared with extrafacial sites, despite being at a more routinely visible part of the body, suggests that there are still opportunities for targeted pigmented lesion public education.

A clinical review of the evidence for the role of ultraviolet radiation in the etiology of cutaneous melanoma

Strong epidemiological evidence exists that solar radiation is causally related to a significant proportion of cutaneous melanoma. The nature of the relationship is, however, complex and the details are not entirely clear. There appears to be a complex interplay between solar exposure in individuals with a characteristic phenotype. Although the exact quantitative and qualitative nature of this exposure is not clear, it is probable that intermittent exposures and intense exposures with consequent sunburns in a high-risk phenotype are critical in increasing the risk of developing melanoma. Despite the lack of complete understanding of this relationship, the evidence is convincing that solar radiation is causally related to cutaneous melanoma and consequently exposures to UV radiation should be reduced from early in life. The preventive measures involve reducing exposure to ambient solar radiation, by avoiding peak exposures, wearing protective outerwear, and using broad-spectrum sunscreens.

Effectiveness of two strategies for dissemination of sun-protection policy in New South Wales primary and secondary schools

With rising rates of skin cancer in Australia, there is a need to examine strategies to reduce sun exposure among children. This study aimed to determine the effectiveness of a multifaceted dissemination strategy compared with a simple mail-out strategy in promoting the adoption of comprehensive SunSmart skin protection policies and practices in primary and secondary schools in New South Wales. It also aimed to examine characteristics of the primary and secondary schools that adopted a comprehensive SunSmart policy before and after the intervention. Four hundred randomly selected primary schools and all 381 high schools in New South Wales were randomised to one of two intervention groups. Pretest and post-test surveys of principals were undertaken in 1991 and 1992. Intervention 1 was a simple mail-out of a sample sun-protection policy kit. Intervention 2 comprised the mail-out of the policy kit and a follow-up mail-out of a staff development module. There was a strong intervention effect on adoption of a comprehensive sun-protection policy in primary schools (21 per cent for the 'mail' group compared with 44 per cent for 'mail and staff support' group) but not in high schools (6 per cent and 11 per cent). There was little relationship between adoption of a comprehensive sun-protection policy and sun-protection practices in primary or secondary schools. Further research is needed to determine the most effective ways of ensuring that adoption of a comprehensive sun-protection policy results in effective implementation of sun-protection practices in schools.

Incidence of invasive cancers following cutaneous malignant melanoma

It has long been suggested that subjects diagnosed with cutaneous malignant melanoma (CMM) have an excess rate of subsequent neoplasms. To provide further quantitative information on the issue, we have considered 1,780 histologically confirmed CMM diagnosed between 1974 and 1994 by the Cancer Registries of the French-speaking Swiss Cantons of Vaud and Neuchatel (760,000 inhabitants) and followed up to the end of 1994 for the occurrence of a second primary. A total of 194 neoplasms was observed vs. 111.7 expected, corresponding to a standardized incidence ratio (SIR) of 1.7 [95% confidence interval (CI) 1.5-2.0]. When skin cancers were excluded, 87 subsequent neoplasms were observed vs. 84.9 expected (SIR 1.0). Significant excess rates were observed for basal cell (SIR 4.4), squamous cell (SIR 3.1) and melanoma (SIR 4.7) of the skin, as well as for prostatic cancer (SIR 2.1). The increased rates of subsequent skin cancer were somewhat larger in males, whereas all the SIRs were systematically greater below age 60. The SIRs of subsequent skin cancer remained above unity for 5 years or longer since diagnosis of CMM, in the absence of a clear pattern in trend with time since diagnosis. The cumulative incidence following CMM was 3% for CMM, 4% for squamous cell and 14% for basal cell carcinoma 20 years after diagnosis of CMM. Our results confirm that patients diagnosed with CMM have excess risks of subsequent melanoma and non-melanomatous skin neoplasms which justify focused prevention and surveillance of skin lesions in these patients. Subjects with CMM do not have any appreciable overall excess of non-skin neoplasms, even after long-term follow-up.

Comparison of the site distribution of melanoma in New Zealand and Canada

A comparison of the site distribution of cutaneous malignant melanoma in New Zealand and Canada was performed. This series deals with 41,331 incident cases registered between 1968 and 1990 and is the largest to date to evaluate the influence of age and gender on the site distribution of melanoma. Site-specific, age-standardized rates per unit surface area and relative tumour density were assessed by gender and country and differences compared with statistical techniques adapted to this context. The age-standardized rates for all sites were higher in New Zealand than in Canada, the ratio being 3.2 for men and 3.8 for women. Occurrence of melanoma was denser for chronically than intermittently exposed sites in both New Zealand and Canada. The highest incidence rate per unit area was for the ears in men which was more than 5 times the rate for the entire body in each country. For each gender, melanomas were relatively commoner on the trunk and the face in Canada, and on the lower limbs in New Zealand. The variations in the site distribution were similar in each country and consistent with the effect of differential patterns of sun exposure between genders. Our results show that the levels of risk of melanoma between phenotypically comparable populations exposed to different amount of UV radiation vary in a site-specific manner, especially for intermittently exposed sites. This suggests that both environmental conditions and lifestyle factors influence the site distribution of melanoma in these two populations.

Trends in mortality from melanoma in Canada and prediction of future rates

A long term increase in incidence of and mortality due to malignant melanoma has been observed in all well documented white populations. The major identified cause of melanoma is sun exposure. One would expect predictions of future atmospheric ozone depletion to lead to an increase in ultraviolet radiation (UVR) and in the effects of sun exposure. We consider age-period data for Canadian malignant malanoma mortality. We fit a multiplicative exponential/logistic (MEL) model to the data and extrapolate to AD 2010 hence yielding point estimates of future rates. We obtain total mortality forecasts by multiplying rates by population estimates. We present standard errors for forecasts. We forecast that melanoma will be a much larger burden on the health care system in the early years of the next century than it is at present. We obtain an age-cohort model by a simple transformation of the age-period model. Also, we obtain unconditional probabilities of death due to melanoma both for age-period and age-cohort models. We discuss the assumptions underlying the MEL model that suggest possible relationships between UVR and melanoma.

Latitude gradients in melanoma incidence and mortality in the non-Maori population of New Zealand

The variation with latitude of incidence and mortality for cutaneous malignant melanoma (CMM) in the non-Maori population of New Zealand was assessed. For those aged 20 to 74 years, the effects of age, time period, birth-cohort, gender, and region (latitude), and some interactions between them were evaluated by log-linear regression methods. Increasing age-standardized incidence and mortality rates with increasing proximity to the equator were found for men and women. These latitude gradients were greater for males than females. The relative risk of melanoma in the most southern part of New Zealand (latitude 44 degrees S) compared with the most northern region (latitude 36 degrees S) was 0.63 (95 percent confidence interval [CI] = 0.60-0.67) for incidence and 0.76 (CI = 0.68-0.86) for mortality, both genders combined. The mean percentage change in CMM rates per degree of latitude for males was greater than those reported in other published studies. Differences between men and women in melanoma risk with latitude suggest that regional sun-behavior patterns or other risk factors may contribute to the latitude gradient observed.

Cutaneous malignant melanoma of the head and neck. Analysis of treatment results and prognostic factors in 581 patients: a report from the Swedish Melanoma Study Group

BACKGROUND

Results of surgical treatment of cutaneous malignant melanoma (CMM) have been highly variable, probably because of patient selection. Therefore, a study of representative patients with this disease was performed.

METHODS

In a defined area of Sweden, 581 patients were analyzed. Clinical records and histopathologic findings were reviewed. The minimum follow-up time was 7 years. Prognostic factors were evaluated by the Cox proportional hazards model.

RESULTS

Evaluation of sex distribution, age, and anatomic site of the primary tumor showed that the patients were representative of all Swedish patients with CMM of the head and neck. The mean patient age at diagnosis was 64 years for both sexes. Fifty-three percent of the patients were women. Female patients had more tumors of the face than did male patients, whereas male patients were overrepresented among patients with tumors of the auricle-external ear canal and scalp-neck area. Localization to the face was observed in 68%, which is an overrepresentation of three to four times when skin surface is taken into consideration. Twenty-four percent of the patients had lentigo maligna melanoma. Only 33% of the patients had superficial spreading melanoma. In univariate analyses, sex, anatomic site of the primary tumor, histogenetic type, Clark level of invasion, and tumor thickness had prognostic power. In a multivariate analysis, tumor thickness, anatomic site of the primary tumor, and sex of the patient were independent prognostic factors.

CONCLUSIONS

In representative patients with CMM of the head and neck, tumor thickness, anatomic site of the primary tumor, and sex of the patients were independent prognostic factors.

C32 human melanoma cell endogenous lectins: characterization and implication in vesicle-mediated melanin transfer to keratinocytes

To optimize skin pigmentation in order to help body prevention against UV radiation, the mechanism of melanin pigment transfer from melanocytes to keratinocytes must be elucidated. Melanin transfer to keratinocytes requires specific recognition between keratinocytes and melanocytes or melanosomes. Cell surface sugar-specific receptor (membrane lectin) expression was studied in human C32 melanoma cells, an amelanotic melanoma, by flow cytometry analysis of neoglycoprotein binding as an approach to the molecular specificity. Sugar receptors on melanocytes are mainly specific for alpha-L-fucose. Their expression is enhanced upon treatment by the diacylglycerol analogue 1-oleoyl-2-acetylglycerol, which can induce melanin synthesis in amelanotic human melanoma cells in a dose-dependent manner. Flow cytometry analyses showed a small-sized population of vesicles distinguishable from large cells by their fluorescence properties upon neoglycoprotein binding. Sorting indicated that the small-sized subpopulation is composed of vesicles produced by melanocytic cells. Upon vesicle formation, a selective concentration of sugar receptors specific for 6-phospho-beta-D-galactosides appears in the resulting melanocytic vesicles. Vesicles are recognized and taken up by cultured keratinocytes and a partial inhibitory effect was obtained upon cell incubation in the presence of neoglycoproteins, indicating a possible participation of sugar receptors in this recognition. The validity for such a model to help in understanding the natural melanin transfer by melanosomes is confirmed by electron microscopy, which demonstrates the presence of melanin inside keratinocytic cells upon incubation with melanocytic vesicles.

Oral contraceptive use and risk of cutaneous malignant melanoma

The relation between cutaneous malignant melanoma (MM) and the use of oral contraceptives (OC) was investigated in a case-control study carried out from 1979 to 1991 among patients in hospitals and clinics in the Philadelphia (PA) and New York City (NY) metropolitan areas (United States). Cases were 615 women under age 70 who recently had been diagnosed with invasive melanoma; controls were 2,107 women of the same ages who had been treated for other conditions unrelated either to OC use or to skin diseases. The cases were categorized as severe or nonsevere based on the depth of invasion of the tumor or the presence or absence of metastases. Among the severe cases, OC use was not associated with MM: the relative risk (RR) estimate for ever-use was 1.1 (95 percent confidence interval [CI] = 0.8-1.5) and the estimate for 10 or more years of use was 1.1 (CI = 0.6-2.1). Nor was risk associated with recent use, long latency, or young age at first use. Among the nonsevere cases, ever-use of oral contraceptives was associated positively with MM (RR = 1.5, CI = 1.1-2.4) but there was no trend with increased duration of use. The findings provide evidence against the hypothesis that OC use increases the risk of malignant melanoma. The elevated estimates among the nonsevere cases most likely reflect selection bias rather than a causal relation.

The geography of non-ocular malignant melanoma in India: its association with latitude, ozone levels and UV light exposure

Ultraviolet light from sunlight is implicated in the aetiology of non-ocular malignant melanoma, mostly from Western studies. This study reports the relation of such melanomas from 7 cancer registries in different parts of India with latitude, altitude, ozone levels and ultraviolet (UV) light exposure. A log linear model was fitted using GLIM, assuming Poisson errors in incidence; linear and non-linear regression techniques were also used. Results show slight negative associations of melanoma with latitude, chi 2 = -3.37, p = 0.07, and statistically non-significant ones with atmospheric ozone levels (r = -0.36, n.s.), and a positive association with UV (r = 0.30, n.s.). Melanoma incidence from 4 places relates in a parabolic curve with latitude (y = 1-0.09 chi 2 + 0.003 chi 2 in males and y = 1.73-0.17 chi 2 + 0.005 chi 2 in females). Patients originally from west coastal ethnic/linguistic communities predominate in Bombay. Geographic patterns of melanoma in Indians are similar with those in white Caucasians. Ultraviolet light exposure may also be involved in its aetiology in non-white Caucasians, such as Indians.

Cutaneous melanoma and sunburns in childhood in a southern European population

A population-based case-control study of 260 patients (74 males and 186 females, mean age = 56) with cutaneous malignant melanoma and 416 controls (211 males and 205 females, mean age = 55) was conducted in Turin, north-west Italy, to examine the relation between timing of sunburns and sun exposure and melanoma risk within a southern European population, which is still relatively little investigated. Particularly elevated risk was associated with history of sunburns in childhood [odds ratio 5.9; 95% confidence interval (CI) 3.6-9.5], and such risk elevation persisted after allowance for other major melanoma risk covariates. Conversely, risk increase from history of severe sunburns lifelong was lower (odds ratio = 1.7; 95% CI: 1.1-2.4) and was eliminated by allowance for type of skin reaction to sun exposure and history of sunburns in childhood. A significant increase in the risk of cutaneous malignant melanoma was also associated with number of weeks spent on holiday at the beach not only as an adult, but also as a child.

Melanoma and sun exposure: contrasts between intermittent and chronic exposure

The evidence relating cutaneous malignant melanoma to previous sun exposure is now very strong. Major northern hemisphere studies consistently show increases in melanoma in association with recreational and vacation activities related to intermittent sun exposure. These studies have also recorded amounts of sun exposure from such activities. Several studies suggest an increased risk related to short periods of intensive exposure in early adult life. In contrast, regular outdoor occupation confers a decreased risk in these same studies. Australian studies, in populations with much higher levels of total sun exposure, do not show such a clear distinction between intermittent and chronic exposure. The evidence is consistent with a complex relationship of melanoma risk to sun exposure, the risk being increased by intermittent exposure to levels of sun which are higher than normal for that individual, but no increased risk or even a decreased risk related to long term chronic exposure. Possible biological mechanisms for this complex relationship are discussed. In the Western Canada Melanoma Study the effects of occupational and recreational exposure are different in form and are independent. The increased risks seen with various measures of sun exposure do not appear to be systematically different for individuals who have a good tanning response as compared to individuals who do not.

Malignant melanomas masquerade--as benign naevi

Malignant melanoma is becoming more common. 'Curable' early, the prognosis worsens quickly with depth and stage. Publicity in Hong Kong led to an increase in the referral and excision rates for 'benign' pigmented lesions. These excisions yielded 5% (3/61) malignant melanomas. It is suggested that aggressive policies of publicity and excision are justified, along with advice on prevention targeted at known high risk groups.

A retrospective mortality study within operating segments of a petroleum company

This retrospective mortality study was conducted among 34,597 oil industry workers in diverse operating segments. Employees were traced through Statistics Canada, and overall mortality (SMR = 0.85) was lower than general population rates and similar to other petrochemical cohorts. The most notable finding was a significant excess of malignant melanoma [observed deaths (N) = 16, SMR = 1.87, 95% CI = 1.07, 3.04], which concentrated among upstream workers (N = 6, SMR = 6.00, 95% CI = 2.19, 13.06), and was directly related to employment duration and latency. Specific substances or hydrocarbon (HC) streams could not be implicated, although possible explanations include dermal HC exposure, ultraviolet light exposure, or a synergistic effect between these two factors. Marketing/transportation workers showed a non-significant excess of multiple myeloma (SMR = 1.81), which was also related to employment duration, latency, and commencement of employment before 1950. Lymphatic cancer, skin cancer, and kidney cancer mortality was not elevated in refinery workers, a finding at odds with some previous refinery worker studies. Although the malignant melanoma and possibly the multiple myeloma mortality patterns are consistent with an occupational link, further studies are needed to investigate the relationship of these diseases with particular exposures.

Indications of future decreasing trends in skin-melanoma mortality among whites in the United States

Trends in skin melanoma death rates during a 35-year period, 1950-84, were analyzed according to age, sex, and birth cohort for whites in the United States. In contrast to upward trends observed for older men and women (i.e., over 40), downward trends were noted for younger age groups. The risk of dying from skin melanoma appears to have peaked for male cohorts born during the 1950s and for female cohorts born during the 1930s. Assuming no future environmental or lifestyle changes, the upward trend in age-adjusted mortality rates, which averaged 2 to 3% per annum since 1950, is projected to discontinue and bend downward by the second decade of the 21st century. Skin melanoma incidence data, which was limited to a series of 12 years (1973-84) and inadequate for cohort analyses, were included to demonstrate that trends in age-specific rates were comparable with those observed for mortality during the overlapping time period. Incidence trends according to anatomical site are also described. These results indicate that baseline data necessary for assessing the potential effects on this disease from future depletions of the ozone layer, and predicted increases of solar ultra-violet radiation exposure, would be improved with the inclusion of cohort data and age-specific trend analyses.

Early detection and prevention of cutaneous malignant melanoma: emphasis on Swedish activities

The incidence of cutaneous malignant melanoma has increased more than the incidence of any other malignant tumour disease in Sweden the last three decades. Parallel to the almost 6% annual increase in incidence there has been a 3% annual increase in mortality. The knowledge of significant risk factors for melanoma (intermittent sun exposure and phenotypic traits related to skin pigmentation and propensity for dysplastic nevi) as well as the relationship between thin tumours and a good prognosis has been used to develop strategies for primary and secondary prevention. In this paper the Swedish programs for education of physicians, nurses and the general population are presented. A nationwide program for the identification and follow-up of individuals with dysplastic nevus syndrome has been initiated. The effects of the programs are followed by population-based melanoma registries.

A commentary on an association of malignant melanoma with non-ultraviolet radiation exposure

There are direct and indirect studies that suggest that non-ultraviolet radiation may be associated with the increasing mortality and incidence of malignant melanoma of the skin. Tangential and supporting evidence for these associations are critically reviewed.

Solar protection issues for schools: policy, practice and recommendations

This study presents findings on solar protection policies and practices in primary and secondary schools in New South Wales, Australia. The findings suggest that policies have been more fully articulated in primary schools than in secondary schools and that there is wide scope for further public health initiatives to protect children from the risk of skin cancer. Little attention has been given to the potential benefits of timetable changes and provision of shade in school environments, although school principals considered the latter would be a successful means of increasing protection. The level of solar education provided in the schools surveyed in our study was minimal, suggesting that urgent attention should be given to incorporating these issues in the school curriculum. Observations of school children's solar protection behaviours suggest that the majority of children used some form of protection in the middle of the day, but the form of protection changed with age. Consideration of more structural and environmental changes is needed to maximise the opportunities for solar protection in schools.

Urban and rural factors in the aetiology of cancer

The incidence of cancer, or the mortality attributed to it, has been compared in urban and rural residents in 13 populations. In each case, the incidence (or mortality) has been higher in the urban areas in each sex, the ratios varying from a minimum of 1.03 to 1 in men in Japan to 1.63 to 1 in men in Denmark. Examination of 26 separate types of cancer showed that 23 tended to be more common in towns, 1 (myeloma) to be evenly distributed, and 2 (cancers of the lip and eye) to be more common in the countryside. The urban excess was greatest for cancers of the bladder, larynx, liver, lung, mouth and pharynx, and oesophagus, and least for leukaemia and non-Hodgkin's lymphoma. It is concluded that differences in personal behaviour (cigarette smoking, alcohol consumption, sexual promiscuity, exposure to ultraviolet light, type of diet, and family size) are the principal factors responsible for the urban excess. Other factors include general atmospheric pollution, occupational hazards, genetic differences in susceptibility, and artefacts of diagnosis and recording. The rural excess was marked for cancer of the lip in both sexes, but less marked and clearly evident only in men for cancer of the eye. Three-quarters of eye cancers are melanomas and the excess incidence in rural areas provides some weak support for the idea that exposure to sunlight contributes to the production of the disease.

Occupational sunlight exposure and melanoma in the U.S. Navy

Melanoma is the second most common cancer, after testicular cancer, in males in the U.S. Navy. A wide range of occupations with varying exposures to sunlight and other possible etiologic agents are present in the Navy. Person-years at risk and cases of malignant melanoma were ascertained using computerized service history and inpatient hospitalization files maintained at the Naval Health Research Center. A total of 176 confirmed cases of melanoma were identified in active-duty white male enlisted Navy personnel during 1974-1984. Risk of melanoma was determined for individual occupations and for occupations grouped by review of job descriptions into three categories of sunlight exposure: (1) indoor, (2) outdoor, or (3) indoor and outdoor. Compared with the U.S. civilian population, personnel in indoor occupations had a higher age-adjusted incidence rate of melanoma, i.e., 10.6 per 100,000 (p = .06). Persons who worked in occupations that required spending time both indoors and outdoors had the lowest rate, i.e., 7.0 per 100,000 (p = .06). Incidence rates of melanoma were higher on the trunk than on the more commonly sunlight-exposed head and arms. Two single occupations were found to have elevated rates of melanoma: (1) aircrew survival equipmentman, SIR = 6.8 (p less than .05); and (2) engineman, SIR = 2.8 (p less than .05). However, there were no cases of melanoma or no excess risk in occupations with similar job descriptions. Findings on the anatomical site of melanoma from this study suggest a protective role for brief, regular exposure to sunlight and fit with recent laboratory studies that have shown vitamin D to suppress growth of malignant melanoma cells in tissue culture. A mechanism is proposed in which vitamin D inhibits previously initiated melanomas from becoming clinically apparent.

UVA-induced tumours in pigmented hairless mice and the carcinogenic risks of tanning with UVA

An animal experiment is presented in which two groups of pigmented hairless mice were exposed daily to suberythemal doses of UVA to study tumourigenesis. The aim of the study was to estimate the carcinogenic risks of tanning by UVA. The pigmented hairless mice, Skh-hr2, were separated by selective breeding into two groups, the "browns" and the "blacks". Both groups were exposed daily to UVA from fluorescent UVA lamps (Philips TL40W/09) purified by rigorously filtering out the shorter wavelengths. No acute actinic damage was observed after any exposure. However, in most UVA exposed animals, especially in the blacks, a marked scratching preceded the development of tumours. Hyperkeratosis was also observed. All animals developed tumours. Histopathologically at least 60% of the tumours were squamous cell carcinomas. Depositions of melanophages were observed, but no melanomas. It is beyond any doubt that UVA is carcinogenic in laboratory animals. The present state of knowledge justifies no preference for tanning with UVA over tanning with UVB.

Changes in cancer incidence in the Swiss Canton of Vaud, 1978-87

Changes in age-standardized cancer registration rates in the Swiss Canton of Vaud (population 530,000) over the two five-year calendar periods 1978-82 and 1983-87 were analyzed. The incidence of occurrence at lung and other tobacco-related sites remained stable (or slightly decreased in males), but showed a substantial increase in females (approximately 40%, from 6.8 to 9.5/100,000 world standard, for lung alone). Other upward trends were observed for skin in both sexes (approaching 50% for melanoma in males), female breast (+8.0%, reaching 69.5/100,000), ovary and urinary tract neoplasms. In contrast, declines were observed not only for stomach and cervix, but also for intestine, gallbladder and endometrium. Consequently, overall total cancer incidence (excluding non-melanomatous skin) declined by 1.1% in males, but increased by 2.7% in females, reaching values of 277.9 and 205.4/100,000, respectively, in 1983-87. The absence of any substantive trends in incidence for cancers of the prostate, testis, brain and multiple myeloma is of potential interest, and represents an important indicator of the uniformly high standard of monitoring by this cancer registration scheme. In a public health perspective, it is discouraging that most of the increases were restricted to cancer sites whose etiology has long been well defined, i.e., tobacco for females and sunshine or other sources of non-ionising radiation, although it is reassuring to be able to document the levelling of tobacco-related cancer incidence in males.