Seasonal variation in frequency of diagnosis of cutaneous malignant melanoma

Impact of the COVID-19 Pandemic on the Incidence and Thickness of Cutaneous Melanoma in Belgium

(1) Background: COVID-19 had a major impact on cancer diagnostics and treatment. Delays in diagnosis of cutaneous melanoma were particularly feared, given the impact on survival and morbidity that comes with advanced stages. Moreover, its incidence in Belgium has been rapidly increasing in recent decades. This Belgian population-level study quantifies the pandemic effect on the number of melanoma diagnoses and Breslow thickness in 2020 and 2021. (2) Methods: In using an automated algorithm, the number of cutaneous melanoma diagnoses and Breslow thickness were extracted from all pathology protocols from 2017-2021 by the Belgian Cancer Registry. Monthly variations, as well as year-to-year differences, were studied. (3) Results: Annual incidence of cutaneous melanoma fell by 1% in 2020, compared to 2019, mainly due to a diagnostic deficit in March, April, and May 2020. An 8% incidence increase occurred in 2021, primarily reflecting an increase in the number of the thinnest melanomas (≤1 mm). Both the mean and median Breslow thicknesses were higher in spring 2020, resulting from an underrepresentation of thinner tumors. However, no particulars stood out on a full-year basis in either 2020 or 2021. (4) Conclusions: Considering the expected incidence increase, we estimate almost 210 melanoma diagnoses were missed in Belgium in 2020, corresponding to 6% of the expected number. This deficit occurred mainly during the first COVID-19 wave. Despite some rebound, the 2021 total was still 3% short of the expected number, leaving around 325 diagnoses remaining pending in 2020 and 2021, corresponding to a two-year deficit of 4.35%. Fortunately, mainly thin melanomas were missed, without any detectable shift toward thicker tumors later in 2020 and or 2021.

No evidence for seasonal variations of the incidence of testicular germ cell tumours in Germany

The pathogenesis of testicular germ cell tumours (GCTs) is still incompletely understood. Any progress in its understanding must derive from observational studies. Recently, it has been suggested that the incidence of GCTs may follow a seasonal pattern based on circannual changes in the Vitamin D serum levels, with maximum incidence rates in winter months. To examine this promising hypothesis, we studied monthly incidence rates of testicular GCTs in Germany by analysing 30,988 GCT cases aged 15-69 years, diagnosed during 2009-2019. Monthly incident case numbers with data regarding histology and patient age were obtained from the Robert Koch Institut, Berlin, along with annual male population counts. We used precision weighting for deriving pooled monthly incidence rates for GCTs of the period 2009-2019. We stratified pooled rates by histology (seminoma and nonseminoma) and age (15-39 and 40-69 years). By assuming a cyclical effect, we used an estimator of the intensity of seasonal occurrence and report seasonal relative risks (RR). The mean monthly incidence rate was 11.93/105 person-months. The seasonal RR for testicular cancer over-all is 1.022 (95% CI 1.000-1.054). The highest seasonal RR was found in the subgroup of nonseminoma aged 15-39 years, with a RR 1.044 (95% CI 1.000-1.112). The comparison of the pooled monthly rates of the winter months (October-March) with the summer months (April-September) revealed a maximum relative difference of 5% (95% CI 1-10%) for nonseminoma, aged 15-39 years. We conclude that there is no evidence of a seasonal variation of incidence rates of testicular cancer. Our results are at odds with an Austrian study, but the present data appear sound because the results were obtained with precision weighted monthly incidence rates in a large population of GCT cases.

Seasonal variation in diagnosis of cutaneous invasive melanoma and cutaneous squamous cell carcinoma: A nationwide study in the Netherlands

BACKGROUND

Currently, there is no study that has reported on the seasonal trends of skin cancer in the Netherlands. This study aimed to investigate seasonal variation in diagnosis of cutaneous melanoma (CM) and cutaneous squamous cell carcinoma (cSCC) focusing on different subgroups.

METHODS

CM diagnosed from 2001 till 2019 and cSCCs from 2001 till 2015 were selected from the Netherlands Cancer Registry. The monthly distribution of CM and cSCC diagnoses were evaluated. Summer-to-winter ratios (SWRs) were calculated overall and stratified by patient and tumour characteristics.

RESULTS

Significant increases in melanoma incidence were noted over the summer months (SWR 1.39 (CI 1.37-1.40)). This increase was less apparent for cSCCs, as higher incidence rates were observed in the months September-November (SWR 1.13 (CI 1.12-1.14)). The seasonal variation of CM was greater in women and younger people, in superficial spreading melanoma and lentigo maligna melanoma, for the extremities, in thinner lesions, and for stage I at diagnosis. The seasonal variation of cSCC was similar for both sexes, most marked in patients 45-69 and ≥ 70, and for the extremities.

CONCLUSIONS

Our findings showed a pronounced seasonal variation in the diagnosis of CM with a peak in the summer months. For cSCC, no evident peak was observed, but an increase in diagnosis was noted in fall. Both CM and cSCC showed strong seasonal effects for the extremities.

Strong Seasonality in the Diagnosis of Skin Melanoma in Italy: The Italian Network of Cancer Registries (AIRTUM) Study

Aim

To evaluate seasonality in the diagnosis of cutaneous melanoma in Italy.

Methods

A total of 16,284 invasive (and 1,235 in situ) cutaneous melanomas incident from 1978 to 2002 in 14 cancer registries belonging to the Italian Network of Cancer Registries (AIRTUM) was analyzed. We used the Walter and Elwood test to evaluate seasonality. The monthly distribution of diagnosis was evaluated for sex, skin site, melanoma morphology and period of diagnosis.

Results

The overall monthly diagnosis of invasive melanoma showed a statistically significant excess around the month of June. The same pattern was present for males and females, across age-groups and periods of time. All skin sites showed a cycling trend, melanoma of the head and neck peaked around April, all the others peaked around June. As regards morphologic types, a cyclic trend was evident for superficial-spreading melanomas (peak around July), for not-specified melanomas (June) and for other histotypes (June). Diagnosis of in situ melanoma peaked in September.

Conclusions

The present study showed that also in Italy melanoma diagnosis has a seasonal trend, with the peak in early summer. It seemed that summer UV exposure, acting both as a late promoter of malignant melanoma development and also increasing the visibility of pigmented skin lesion, may be relevant to explain such a peak.

Climatic Factors and Epidemiologic Characteristics of Head and Neck Skin Malignancies in Osijek Baranja County, Croatia

AIM

The aim of this study was to investigate and compare the incidence and epidemiological characteristics of head and/or neck skin malignancies in Osijek-Baranja County, Croatia, and to connect them with relative climatic indicators such as the number and intensity of sunny and cloudy days over a longer period of time.

METHODS

The study included patients from Osijek Baranja County with confirmed pathohistological diagnosis of the head and/or neck malignancies from January 1, 2004 to December 31, 2012. The patients were analyzed according to gender, age, residence, occupation, type and location of the neoplasm, and hair and eye colour. The analysis of climatic elements (mean monthly and annual cloudiness values, mean monthly and annual sum values of sunny days) for a period of 50 years (1961-2011) based on the data of the Croatian Meteorological and Hydrological Service for the investigated area was performed.

RESULTS

The study included a total of 2,952 patients: 1,487 (50.4%) males and 1,465 (49.6%) females, representing the estimated annual incidence of 104/100,000. The mean age was 72 years. The patients were mostly from rural areas, 1,952 (66.2%); 2,137 (72.4%) worked outdoors: 907 farmers (42.4%) and 889 construction workers (41.6%). Given the type of neoplasm, the most common was a basal cell cancer (BCC) in 2,160 patients (73.2%). Malignant melanoma was found in 93 patients (3.1%). The most common localizations were face (839 cases, 28.7%) and nose (643 cases, 22.0%). Males had a significantly higher number of planocellular malignancies--341 (56.6%) than females--262 (43.4%) (p=0.005). The median age of the patients was 67 years. There were no significant differences in types of malignancies, place of residence, workplace, or occupation (with respect to working outdoors or indoors). It has been shown that the ears and lips are significantly more affected by squamous cell malignancies (p=0.039 and p<0.001) compared to the neck, eye and head with malignant melanoma (p=0.004, p<0.001, and p=0.026) and the nose where basal cell neoplasms (p=0.002) prevail. There were no significant differences in the type and frequency of malignant neoplasms in relation to hair and eye colour of the patients. The last 50 years in Osijek-Baranja County have seen a declining trend in the number of cloudy days and upward trend in the mean annual sum of sunny days. When compared, the increase in sunny days results in a higher number of patients suffering from malignant melanoma (ρ=0.695, p=0.038).

CONCLUSION

It is obvious that malignant neoplasms of the skin, head and neck occur after decades of exposure, and as a cumulative effect of exposure to risk factors. A direct exposure to sun seems to play an important role, especially with regard to melanoma. Nevertheless, further research is needed.

Seasonal variation in cutaneous melanoma incidence, link with recent UV levels: a population-based study in Belgium (2006-2011)

Our objective was to test the hypothesis of a short-term late-promoting effect of ultraviolet (UV) exposure on the development of cutaneous melanoma as an explanation for the summer peak in melanoma incidence. Therefore, we studied seasonal variation in melanoma incidence in relation to recent UV levels by direct UV measurements. Data from the Belgian Cancer Registry on invasive cutaneous melanoma diagnosed during 2006-2011 were used for analysis. Daily data on UV measurements in Belgium were obtained from the Royal Meteorological Institute. Simple and multiple negative binomial regression models were used to investigate the influence of recent UV levels on melanoma incidence. The sum of the mean UV doses in the 2 months before diagnosis was used as a proxy for recent UV exposure in the population. To include variable sunburn risks during the year, the categorical variable 'semester' was created. The incidence of melanoma in Belgium shows a distinct seasonal variation, with peaks in June or July. We found that part of this variation could be explained by the variation in dermatologic activity and, therefore, used this as an offset in our models. We found a linear relationship between melanoma incidence and UV dose in the 2 months preceding the diagnosis. UV levels had more impact in the first semester. The effect of UV levels was not modified by sex nor age. The interaction between anatomical site and UV levels was significant (P=0.002) and showed a higher effect on the upper and lower limbs compared with the head and neck and trunk.

Replacing surrogate measures by direct quantification of ultraviolet radiation exposure in registry-based analyses of seasonality of melanoma diagnoses

Seasonal variation in melanoma diagnoses has been observed in numerous studies that used calendar time indicators. Depending on the latitude (and altitude) of the study region, the magnitude of seasonal and year-to-year variation of ultraviolet radiation (UVR) is neglected in these studies. An alternative approach comprises the direct incorporation of UVR measurements into such analyses. The aim of this investigation is a comparative evaluation of these approaches. The population-based Bavarian cancer registry recorded 11 901 incident melanoma cases between 2003 and 2008 that were used for the analysis. UVR intensity data for the same period were available from the solar radiation station at Munich-Neuherberg. Negative binomial regression modelling yielded adjusted relative risks (RR) controlled for year of diagnosis and age in 16 subgroups defined by sex, Breslow thickness and localization. Overall, the analyses showed slightly differing yet consistent results for exposure effects in subgroups. Melanoma evolving on the extremities showed the most pronounced association with increasing level of the UV index among men [e.g. RR=1.086, 95% confidence interval (CI) 1.054-1.119, and RR=1.102, 95% CI 1.046-1.161, for thin and thick melanoma on the upper limbs, respectively] and women (e.g. RR=1.088, 95% CI 1.058-1.119, and RR=1.056, 95% CI 1.010-1.103, for thin and thick melanoma on the lower limbs, respectively). Our analysis provides a benchmark for international comparisons and synthesis of epidemiologic evidence of seasonal variability in melanoma diagnoses. Future studies should use direct UVR measures to enable pooling of risk estimates and resolve remaining inconsistencies potentially resulting from latitudinal differences in exposure between international studies.

Seasonal variation in diagnosis of invasive cutaneous melanoma in Eastern England and Scotland

BACKGROUND

Worldwide, the incidence of cutaneous melanoma has been reported to be highest in the summer and lowest in the winter. Northern Irish data suggested seasonal variation for women only, especially those with thinner melanomas, sited on limbs. We interrogated two larger UK cancer registries for temporal differences in melanoma diagnosis and associated patient characteristics.

METHODS

Melanomas diagnosed from 2006 to 2010 in the Eastern England and Scottish cancer registries (n=11,611) were analysed by month of diagnosis, patient demographics and melanoma characteristics, using descriptive and multivariate modelling methods.

RESULTS

More patients with melanoma were diagnosed in the summer months (June 9.9%, July 9.7%, August 9.8%) than the winter months (December 7.2%, January 7.2%, February 7.1%) and this pattern was consistent in both regions. There was evidence that the seasonal patterns varied by sex (p=0.015), melanoma thickness (p=0.002), body site (p=0.006), and type (superficial spreading melanomas p=0.005). The seasonal variation was greatest for diagnosis of melanomas occurring on the limbs.

CONCLUSION

This study has confirmed seasonal variation in melanoma diagnosis in Eastern England and Scotland across almost all population demographics and melanoma characteristics studied, with higher numbers diagnosed in the summer months, particularly on the limbs. Seasonal patterns in skin awareness and related help-seeking are likely to be implicated. Targeted patient interventions to increase sun awareness and encourage year-long skin inspection are warranted.

Is melanoma survival influenced by month of diagnosis?

BACKGROUND

Despite being a well-documented phenomenon, seasonal variation in the incidence of cutaneous melanoma is poorly understood, and data on the seasonality of melanoma survival are scarce. We sought to explore the seasonal variation in melanoma incidence and survival in Belgium and to assess the characteristics and outcomes of cases diagnosed during the seasonal peak.

METHODS

All cases of invasive cutaneous melanoma-patients over 15 years of age and registered by the Belgian Cancer Registry (BCR) from 2004 to 2009-were included (n=9782). Monthly variations in incidence were estimated by the ratio of the number of cases diagnosed each month to that diagnosed in January (Rmonth/January) using Nam's method. The observed and relative 5-year survival rates were adjusted on patient and tumour characteristics using Cox proportional hazards regression models and generalised linear models with a Poisson error structure, respectively.

RESULTS

A peak in melanoma incidence was observed in June (RJune/January=1.64, 95% confidence interval (CI)=1.54-1.73). The 5-year observed survival (OS) and relative survival (RS) rates were significantly higher for patients diagnosed in June compared with other months (OSJune=84%, 95%CI=81-86 versus OSOthermonths=79%, 95%CI=78-80; RSJune=93%, 95%CI=90-95 versus RSothermonths=87%, 95%CI=86-88). After adjustment, the 5-year OS remained significantly higher for patients diagnosed in June (hazard ratioJune=0.78, 95%CI=0.62-0.98); however, the 5-year RS was no longer significantly different for patients diagnosed in June compared with other months (relative excess riskJune=1.16, 95%CI=0.73-1.84).

CONCLUSIONS

This study demonstrated a seasonal variation in melanoma incidence in Belgium with a peak in June for the period 2004-2009. When adjusted for patient and tumour characteristics, patients diagnosed in June had higher observed survival rates, but relative survival rates did not differ. Our findings do not support an influence of season of diagnosis on melanoma prognosis.

Exponentially increasing incidences of cutaneous malignant melanoma in Europe correlate with low personal annual UV doses and suggests 2 major risk factors

For several decades the incidence of cutaneous malignant melanoma (CMM) steadily increased in fair-skinned, indoor-working people around the world. Scientists think poor tanning ability resulting in sunburns initiate CMM, but they do not understand why the incidence continues to increase despite the increased use of sunscreens and formulations offering more protection. This paradox, along with lower incidences of CMM in outdoor workers, although they have significantly higher annual UV doses than indoor workers have, perplexes scientists. We found a temporal exponential increase in the CMM incidence indicating second-order reaction kinetics revealing the existence of 2 major risk factors. From epidemiology studies, we know one major risk factor for getting CMM is poor tanning ability and we now propose the other major risk factor may be the Human Papilloma Virus (HPV) because clinicians find β HPVs in over half the biopsies. Moreover, we uncovered yet another paradox; the increasing CMM incidences significantly correlate with decreasing personal annual UV dose, a proxy for low vitamin D3 levels. We also discovered the incidence of CMM significantly increased with decreasing personal annual UV dose from 1960, when it was almost insignificant, to 2000. UV and other DNA-damaging agents can activate viruses, and UV-induced cytokines can hide HPV from immune surveillance, which may explain why CMM also occurs in anatomical locations where the sun does not shine. Thus, we propose the 2 major risk factors for getting CMM are intermittent UV exposures that result in low cutaneous levels of vitamin D3 and possibly viral infection.

Seasonality of cutaneous melanoma diagnoses: a comprehensive comparison of results in Bavaria and Northern Ireland

Ultraviolet radiation is an established skin carcinogen. By analysing the seasonality of melanoma diagnoses, the effect of this risk factor can be examined indirectly. However, previous studies yielded conflicting results, because of vastly differing analytical methods and diverse study designs. Therefore, to validate the findings by Chaillol and colleagues based on 3868 melanoma diagnoses from Northern Ireland, we used an identical methodology to examine the seasonal effects on monthly incidences of 11,901 cutaneous malignant melanoma cases registered from 2003 until 2008 in Bavaria, Germany. Multivariable regression models for count data were used to estimate the effect of seasons while taking into account sex, age, year of diagnosis, Breslow thickness and anatomical site. Point and interval estimates of the adjusted relative risks associated with seasons were compared with the findings of the Irish study. Both analyses demonstrated a promoting effect of intermittent ultraviolet radiation on cutaneous melanoma of a thickness of 2 mm or less evolving on the extremities, whereas no seasonality for melanomas on the trunk was evident. Differences were identified with regard to thick melanomas. In the present analysis, only melanomas with a Breslow thickness of more than 2 mm were also found to be associated with season, in particular, the melanomas on the limbs. Hence, in contrast to the data of, and to the interpretation by, Chaillol and colleagues, an effect of ultraviolet radiation on melanoma progression from thin to thick cannot be excluded.

Analysis of trends and seasonal variation in primary cutaneous melanoma: an Irish study

A seasonal variation in the presentation of cutaneous melanoma has been documented in several studies. We performed a retrospective review of primary cutaneous melanomas (n = 263) from our institution to examine whether the seasonal patterns of presentation noted in the literature would be similar in Ireland, a climate with low ambient sunshine. A summer : winter ratio was determined for age, gender, subtype, location and Breslow thickness. We found an increase in total numbers of melanomas, particularly in men. The summer : winter ratio was 2.39 for all patients (95% CI 1.60-3.57, P < 0.001), with seasonal variations noted for location, thickness and subtype (excluding lentigo). Melanomas presenting over the summer tended towards a greater Breslow thickness than did those presenting in winter. This subclassification of primary cutaneous melanoma with summer : winter ratios based on patient and tumour characteristics gave remarkably similar results to previously published reports, notwithstanding the low levels of annual ambient sunshine in Ireland.

Space-time clustering and seasonality in diagnosing skin cancers in Wallonia (south-east Belgium)

BACKGROUND

In Westernized populations, the number of diagnosed cases of primary cutaneous cancers, particularly malignant melanomas and basal cell carcinomas (BCC), has been previously shown to fluctuate during specific periods of the year.

OBJECTIVE AND METHOD

The aim of the present 6-year study was to explore the seasonality if any in skin cancer detection in Wallonia (south-east Belgium).

RESULTS

For both malignant melanomas and BCC late spring/early summer and mid-autumn were the periods of highest diagnosis prevalence irrespective of gender. The amplitude of this bimodal evolution remained within the range of 2 standard deviations around the monthly means. Similar seasonal variations were also found in non-neoplastic controls consisting of laboratory samplings of onychomycoses and non-infectious onychodystrophies.

CONCLUSION

There is reason to believe that this timing and rhythm is unrelated to any specific cancer chronomics. Rather, the present findings suggest unspecific seasonality in diagnosing skin disorders including malignancies. A variable patient awareness of changing aspects of the skin according to seasons probably represents the major influence of the described space-time clustering of skin cancer diagnosis.

Variation in Incidence and Fatality of Melanoma by Season of Diagnosis in New South Wales, Australia

Seasonal variation in cutaneous melanoma incidence with a summer peak is poorly understood. It has been hypothesized to be due to increased diagnosis in summer or a late-promoting effect of sun exposure. We analyzed the characteristics of incident cases of cutaneous melanoma and their outcome by season of diagnosis in the population of New South Wales, Australia. Cases of melanoma (25,845 cases; 10,869 females and 14,976 males) were registered by the New South Wales Central Cancer Registry in 1989 to 1998. There was significant seasonal variation in incidence (P < 0.0001, Nam test). The summer to winter ratio was greater for women, younger people, lesions on the limbs, and superficial spreading melanoma. Melanomas were thicker in winter than in summer (medians 0.75 and 0.70 mm, respectively; P < 0.0001, Kruskal-Wallis test). Cases were followed for a median of 63 months and 2,710 (10.5%) died from their melanoma. Fatality from melanoma was lower for melanomas diagnosed in summer than winter (relative fatality = 0.72; 95% confidence interval, 0.65-0.81); the 5-year survival rate was 92.1% for diagnosis in summer and 89.0% for diagnosis in winter. This result remained significant after adjustment for year of diagnosis, age, sex, Breslow thickness, anatomic location, and histologic type (relative fatality = 0.82; 95% confidence interval, 0.72-0.94). Seasonality in melanoma incidence is probably caused mainly by increased and earlier diagnosis in summer, although a late-stage promotional effect of sun exposure cannot be excluded completely. Earlier diagnosis may also reduce fatality when melanoma is diagnosed in summer. Independence of variation in fatality with season from seasonal variation in thickness, however, suggests that sun exposure around the time of diagnosis decreases fatality of melanoma.

Cutaneous melanoma and intervention strategies to reduce tumor-related mortality: what we know, what we don't know, and what we think we know that isn't so

The care of patients who have cutaneous melanoma (CM) has undergone a dramatic change during the past five decades. In an increasing majority of cases, CM is being discovered in a premetastatic phase of tumor progression. Most patients are being treated in the ambulatory setting with a minimum of inconvenience and economic cost, and modest re-excision margins have largely replaced the mutilating surgical exonerations that were once standard only four decades ago. Histopathologic assessment of the primary tumor is the most widely used staging procedure to determine who is most likely to develop metastatic disease. For patients who develop distant metastases, there is no therapy currently available, based on large-scale randomized trials, that will prolong patient survival. Therefore, establishing an early diagnosis in a premetastatic phase of tumor development must be the overriding goal of any intervention strategy that seeks to reduce CM-related mortality. Unfortunately, as a result of public messages that emphasize the role of ultraviolet radiation (UVR) exposure in tumor development, most general physicians and lay people believe that most if not all cases of CM are the direct result of UVR exposure. In fact, we do not know the case fraction of CM directly attributable to UVR, and the unintended consequences of current messages directly linking UVR exposure and CM development may be thwarting the primary intervention goal of reducing tumor-related mortality. More likely to have an immediate positive impact on CM-related mortality are public messages that encourage skin awareness and self-examination by patients, total skin screening examinations by physicians during routine care, and periodic lifetime surveillance of patients determined to have a high CM risk based on identifiable historic and phenotypic traits.

Poly(adenosine diphosphate-ribose) polymerase 1 expression in malignant melanomas from photoexposed areas of the head and neck region

The family of the poly(adenosine diphosphate-ribose) polymerase (PARP) proteins is directly involved in genomic stability, DNA repair, and apoptosis by DNA damage. In this study, we evaluated the role of PARP-1 in melanoma and its prognostic importance. We studied by immunohistochemistry and Western blot analysis PARP-1 expression in a selected series of 80 primary melanoma of the head and neck region. The results were correlated with tumor thickness and patient's outcome. A follow-up of at least 3 years was available. Fifteen cases of benign melanocytic nevi were used as controls. Normal melanocytes showed only scattered, focal nuclear positivity and were considered as negative for PARP-1 expression by immunohistochemistry (score, 0). Thirty cases of melanoma (37.5%) showed nuclear expression of PARP-1 in both radial and vertical growth phases. Western blot analysis showed the presence of a high signal for full-length PARP-1 only in the cases with high immunohistochemical (nuclear) expression of protein (score, ++/+++) in both radial and vertical growth phase. A significant correlation was present between PARP-1 expression in vertical growth phase and the thickness of tumor lesion (P = .014); all but one tumor measuring less than 0.75 mm showed no or low PARP-1 expression. No correlation was found between PARP-1 expression in radial growth phase and tumor thickness (P = .38, data not shown). These data suggest that PARP-1 overexpression is a potential novel molecular marker of aggressive cutaneous malignant melanoma and a direct correlation between PARP-1-mediated inhibition of the apoptosis and biologic behavior of cutaneous malignant melanoma.

Seasonal variation in the occurrence of cutaneous melanoma in Europe: influence of latitude. An analysis using the EUROCARE group of registries

The aim of our study was to analyse seasonal variations in melanoma incidence in Europe. Data from 28117 cutaneous melanoma cases reported during 1978-1993 to the EUROCARE group of registries were analysed. There is a clear summer peak in incidence in Western countries (summer-winter ratio: 1.31 P < 0.0001; Nam's test), which was not observed in Central Europe (ratio: 1.06; P = 0.0699). The amplitude of seasonality is higher for females (ratio = 1.38, 95% Confidence Interval (CI) [1.31-1.44]) than for males (ratio = 1.21 95%CI [1.14-1.29]). It is also higher for upper and lower limbs (1.44 and 1.46, respectively), than for head and neck or trunk regions (1.09 and 1.20, respectively). The amplitude of seasonality also varies with latitude and increases with time: in a linear regression adjusting for age, gender and anatomical localisation, the date of diagnosis was significantly closer to summer solstice with decreasing latitude (P = 0.0005) and for more recent year of diagnosis (P = 0.0123). The effect of latitude on the amplitude of the seasonal variation in melanoma incidence in Europe may be an indicator of ultraviolet B (UVB) exposure. Furthermore, an increase in intentional sun exposure could lead to an increase in melanoma promotion and thus to an increase in the amplitude of seasonal variation.

Seasonal variations in the diagnosis of cutaneous melanoma

Seasonal patterns in diagnosis were examined in 7836 patients with cutaneous melanoma (clinical stage I and II) documented at the Department of Dermatology and Allergology at Ludwig-Maximilian-University in Munich, Germany, between 1977 and 2000. Of these patients, 2362 were first given a diagnosis in the summer months (June-August) and 1757 were first given a diagnosis in the winter months (December-February). A summer-to-winter ratio was determined for sex, age, anatomic tumor site, histopathologic subtype, and tumor thickness. The summer-to-winter ratio was 1.34 (95% confidence interval: 1.27-1.43) for all patients, with a ratio of 1.22 (95% confidence interval: 1.12-1.33) for men and 1.47 (95% confidence interval: 1.35-1.60) for women. The frequency of diagnosis of cutaneous melanoma was seasonal for all age classes, for all anatomic tumor sites, for all histopathologic subtypes except acrolentiginous melanomas, and for melanomas with a tumor thickness <3.0 mm. Comparing subgroups of the above-mentioned clinical and histopathologic parameters, significant differences could be observed for sex and anatomic tumor site. On the basis of this data, possible explanations for the diagnostic summer peak may be a greater awareness as a result of clothing habits in summertime or because of incurred sunburns in patients with skin type I and II, and the influence of public-health campaigns usually performed at the beginning of summer.

Seasonal effect upon excision of acquired melanocytic proliferations

BACKGROUND

Acquired melanocytic proliferations (AMPs) are excised throughout the year. Questions exist concerning seasonal variation in these excisions.

OBJECTIVE

To investigate whether AMPs are removed more often during the spring-summer seasons than in the fall-winter and whether the percentage of benign nevi, dysplastic nevi and melanoma varies according to season.

DESIGN

Retrospective analysis of 4794 histologically confirmed biopsies of AMPs was performed.

RESULTS

A total of 2802 of the 4794 lesions (58%) were removed during the spring-summer season. These results confirm that seasonal variation in removal of AMPs does occur, and that removal peaks during the warmer months. In addition, the increased numbers of removals were accounted for by increases in benign pigmented lesion removals.

CONCLUSIONS

Many etiologic factors can be suggested for increased removal of AMPs during the warmer months. Reasons may include the cosmetic desires of the patient and clothing choices resulting in increased awareness of pigmented lesions. Increases in the number of skin cancer prevention programs offered by dermatologists in the spring also have a large impact on the awareness of the general population and potentially contribute to the seasonal variation.

Photoperiod modulates melanoma growth in C57BL/6 mice

Seasonal variations can be found in almost any parameter of an organism's biochemistry, physiology, endocrinology, and behaviour. This phenomenon, generally called photoperiodism, results from one of the major functions of the circadian system, i.e. the translation of environmental information into rhythmic intraorganismic signals, which then regulate or influence physiology and pathology. We induced melanoma in three groups of syngeneic C57BL/6 mice synchronised to different photoperiods (8, 12, or 18 h of light within 24-h days) by subcutaneous injections of HFH18 melanoma cell suspensions. All animals from all three photoperiodic groups developed exponentially growing tumors. The average tumor volume on day 31 post injection was significantly smaller in animals exposed to light/dark conditions (LD) 8 : 16 h as compared with animals held in LD 18 : 6 h and intermediate in animals from the equinox group. These results indicate that C57BL/6 mice react to photoperiod, which can exert a significant effect on tumor growth.

Seasonal variation in the diagnosis of cancer: a study based on national cancer registration in Sweden

Data from the Swedish Cancer Register 1987-1996 were used to examine seasonal trends in the diagnosis of cancer. For melanomas, prostate, breast and thyroid cancer there were clear seasonal variations with reductions in the number of cases reported during the summer and December that are likely to reflect mainly hospital delays.

A role for photoproducts of vitamin D in the etiology of cutaneous melanoma?

Several clinical and epidemiological aspects of cutaneous melanoma seem anomalous because they contrast with other sunlight-associated skin cancers. For example, persons with the greatest risk of melanoma are not those with the greatest cumulative solar exposure, the anatomic areas that receive the most solar exposure are not preferentially affected, and the incidence of the disease is seasonal, with more cases reported in summer than winter. This article discusses the synthesis and biologic effects of vitamin D photoproducts and suggests that sun-related local skin effects, mediated by vitamin D photoproducts, on melanocytes previously damaged by excessive solar exposure may help explain the seemingly anomalous aspects of melanoma.

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

Melanoma risk among subjects from Germany, France and Belgium who had lived for 1 year or more in sunny climates was examined in a one-to-one unmatched case-control study conducted among white subjects 20 years old or more. A total of 412 consecutive patients with melanoma diagnosed from 1 January 1991 onwards, were derived from hospital registers; 445 controls were randomly chosen in the same municipality as the cases. After adjustment for host characteristics, melanoma risk associated with residence in a sunny area was 2.7 (95% CI: 1.4-5.2), increasing to 4.7 (95% CI: 1.4-13.5) if subjects sought a suntan when residing in sunny climates, and to 4.3 (95% CI: 1.7-11.1) if subjects arrived before the age of 10 years in the sunny area. Residence in sunny areas and recreational sun exposure seemed to combine their effects on melanoma risk. Increase in melanoma risk conveyed by deliberate sun exposure during adulthood was highest among subjects who had lived in sunny areas as a child or adolescent and lowest among subjects who had never resided in sunny areas. Our results support conclusions from migrant studies that indicated that childhood is a critical period of either vulnerability to solar radiation or more frequent exposures to melanoma risk factors. They also suggest that moderate sun exposure of an adult who was heavily sun exposed in childhood is associated with a higher melanoma risk than that of high sun exposure of an adult who was sun protected in childhood.