Aust, J.Demi, (1982)23. 105

INCIDENCE AND REPORTING OF CUTANEOUS MELANOMAIN QUEENSLAND

GREEN*

Brisbane

SUMMARY .

New cases of primary cutaneous tnelanoma occurring in Queensland in a recenttwelve month period were ascertained from pathology records. The reported incidencerates have risen, even in a two and a half year period, from 32.7 in 1977 to 39.6 perWO, 000 population in 1979-80. The main prognostic features are presented and confirman increased proportion of thin tumours, particularly of the tentigo maligna melanotnatype. To determine underlying medical and public awareness of melanoma a randomsatnple of the total year's patients was interviewed to establish how the tumours werefirst noticed. This factor of awareness in an educated high-risk community may affectthe observed incidence patterns of malignant tnelanoma and should be considered whenseeking to explain the reported rising trends. ,•- , .

INTRODUCTION

During the last 15 years, the annual number ofcases of melanoma of the skin in Queensland hasbeen increasing, consistent with rising trendsreported world-wide.'' A doubling in incidencewas seen in the 10 years to 1977: from 16.4 to32.7 per 100,000 population.^ A detailedepidemiological study of ineident cases ofcutaneous melanoma diagnosed in one year fromJuly 1, 1979 was undertaken to investigate thisobserved rise.

Some factors which may contribute are: a truerise in disease incidence; an increase in thereporting of melanoma; and reporting at anearlier stage. The relative effect of the last twofactors on the number of cases diagnosed inQueensland may be important^* in view of thewidespread publicity regarding skin cancer andmelanoma.

* Queensland Instilule Medical Research and Departmentof Social and Prevenlive Medicine, University ofQueensland.

Address for reprints: Dr. Adcle Green, QueenslandInstitute of Medical Research, Bramston Terrace, Brisbane,Qtjeensland 4(K)6.

This paper reports the results of the mostrecent survey of the incidence and prognosticfeatures of melanoma in Queensland. Interviewdata obtained from a random subset of thepatients regarding their discovery of someabnormality are also presented as a possiblegauge of the community's awareness ofmalignant melanoma.

SUBJECTS AND METHODS

The population studied consisted of allpatients with first primary cutaneous melanomadiagnosed in Queensland in the twelve monthperiod from July 1, 1979 to June 30, 1980. Eachof the state's 24 pathology laboratoriesparticipated in the study and information wasprovided for 871 incident patients who wereresidents of Queensland at time of histologicaldiagnosis.

Histopathological eriteria requested includeddetails of Clark's classification* of the in situcomponent of the lesion and tumour thickness.''Other particulars supplied by the pathologylaboratories included the age and sex of thepatient and the anatomical site of the lesion.

106 A DELE GREEN

Of the total a random sample of 236 patientswas interviewed. Using a standard questionnaire,the interviewer asked respondents how they hadfirst become aware of their lesions: agents whofirst noticed the melanoma were categorized as"self, "doetor" or some "other" lay person. Alldata were gathered by a single interviewer (A.G.)and were coded for eomputer analysis.

For all patients key features of sex and agedistributions, site distribution and tumour thick-ness were analysed in relation to each of thethree major histologieal types; superficialspreading melanoma (SSM), lentigo maligna(melanoma) (LMIM]) and melanoma showing noin situ component (NIS or nodular). For thesecond part of the study, the patient's sex, andthe site and type of melanoma were furtherrelated to the prospects of its being brought tomedical attention, using the results of the 236patient interviews.

RESULTS

Since the large increase recorded in 1977' thereported ineidence of cutaneous melanoma inQueensland has continued to climb. Eighthundred and seventy-one first primary casesdiagnosed between July 1, 1979 and June 30,1980 represent a erude annual ineidence rate of39.6 per 100,000 population. Of these cases, 416(48%) were in men and 455 (52%) were inwomen.

The histological classifieation of all tumours isshown in Table 1. SSM occurred most frequentlyoverall (57% of the total) and was slightly morecommon in women. Eighty-one percent of al!SSM tumours were invasive. LM and LM(M)constituted 23% of melanomas reported and aquarter of these were invasive at time ofdiagnosis (LMIMI). Fifteen percent of cases wereclassified as NIS or nodular type.

When these three main sub-types wereconsidered separately, characteristics of age ofpatient and site and thickness of tumour wereseen to vary greatly (Fig. 1). In women, SSMoccurred predominantly in younger age groups,mostly on the trunk and lower limb, whilenodular melanoma showed increasing propor-tions with increasing age, with the lower limb

TABLE 1

Histotogieat Ciassifieation of ati Tumours, 1979-80

Ciassifieation Sex Distribution

Mate (n = 4I6) Femate (n = 455)

Superficial spreadingmelanoma

Level 1Invasive

Lcnligo maligna(melanoma)

Level IInvasive

Melanoma wilh no in-silu componentAcral lenliginousIndeterminateUnspecified

220 (53% 136 (9%)

184 (44%)

101 (24%)84 (20%)17 (4%)

73 (18%)3 (1%)

17 (4%)2 (0,4%)

279 (61%)60 tl3%)

219 (48%)

100 (22%)64 (14%)36

53 (12%)1 (0.2%)

12 (3%)10 (2%)

being the major site. Men showed a similar agepattern for the nodular melanomas whereas SSMshowed no particular age pattern and the trunkwas the major site for both types.

LM(M) varied least between the sexes,inereasing to a peak in the 60 69 year age group,with the head and neck being the predominant,though not the only site in both, men andwomen.

With respect to measured tumour thickness,most SSM and LM(M) tumours were thin, incontrast to the majority of nodular melanomas.

The details of lesion reeognition prior todiagnosis, as elieited from the 236 randomlyehosen patients, are summarized in Table 2.Three quarters of nodular melanomas and abouthalf of SSM and LM(M) lesions were notieed bypatients.

Significantly more women than men notieedtheir own lesions (X?-11.92,p<.001). Thiseould not be explained by their differing sitedistributions. For the relatively inaccessible backand shoulders, the sexes showed approximatelythe same propensity to notice tumours onthemselves; and doctors and other lay peoplenoticed similar proportions of lesions there.However for the head and neck, a siteuniversally accessible and showing similarnumbers of tumours in each sex, womenreported 77% self-notieed, compared with only36% of men who were aware of melanomashere.

CUTANEOUS MELANOMA IN QUEENSLAND 107

5 S M LMW)

80 60 40 20 0 ZD 40 40 80 80 60 40 20 0 20 40 SO 80 BO 60 40 20 0 20 40 BO 80

FIGURE I — Comparison of cases in major histological classes, showing distributions of patient age, and tumour siteand thicktiess.

DISCUSSION

Although the incidence of cutaneousmelanoma in Queensland rose from 32.7 in 1977^to 39.6 per 100,000 population in 1979-80, thiscould be attributed largely to the rise in onehistologieal sub type: LM{M), which constituted7% of diagnosed cases in 1967, rising to 15% in1977 and to 23% of all lesions in the presentstudy. The proportion of tumours falling into theSSM class has varied little in the last decade;whereas the nodular class which is generallyinvasive' when first seen, comprised 28% of alllesions diagnosed in 1967, but only 15% of thetotals in both 1977^ and 1979 80.

The patients' ages and the thickness of thetumours showed distributions similar to previousreports."** On the other hand, some interestingfeatures emerged from the type-specific data onthe site of tumour occurrence. The lower limbhas been reported as the predominant site fornon-LM(M) tumours occurring in women;'" andalthough this was seen with nodular melanomasin the present study, the major group, SSM,

appeared as frequently on the trunk as on thelower limbs. Furthermore, LM(M), classicallyseen on the head and neck, has been seen onother sites in 38% of the present series of 201patients. In men, one quarter occurred on thetrunk, while in women the other chief sites werethe limbs: 17% on the upper and 11% on thelower limb.

However, the above comparative data fail toanswer the question of how much of the ob-served increase in incidence can be attributed toa true rise in the disease. LM(M), as distinct fromthe other types of melanoma, is regarded as beingassociated with repeated exposure to the sun."On this basis a true rise in LM(M) frequency mayindeed have occurred: the past two decades haveseen a proliferation of seaside resorts inQueensland, the popularity of which isassociated with increased affluence and leisuretime.

The part played by increased reporting ofmelanoma may also be important but is difficultto assess, as there are no known studies that have

108 ADELE GREEN

TABLE 2Distribution of tumours as first detected by various agentsaccording to

(a) class of melanotna • :(b) sex of patient(e) site of tutnour and sex of patient

(a) HistoloKical Class

SSM(n=l4ULM(M) tn = 49)NIS in = 36)

(b) Sex

Male (n= 120)F e m a l e ( n = 116)

(c) Site of tumour/andsex of pattcntHead and neckMale tn = 28)Female (n = 26)

Back and shouldersMale (n = 48)Female (n= 18)Upper limbMale(n= 11)Female (n = 23)Lower limbMale In =16)F e m a l e (n = 41)Chest and abdomenM a l e ( n = 17)Female tn = 8)

Agent

Self

to first delect lesion

OtherDoctor non medical

Percentage of Cases

535375

4668

3677

4239

5548

6981

47100

26313

2620

3619

2733

939

07

410

211622

2812

294

3128

3613

3112

120

addressed this aspect. Increased attention tomelanocytie lesions hy the medical professioncould affect the clinician's recognition and thepathologist's reporting of melanoma. If over-diagnosis by clinicians or misclassification ofmelanomas by pathoiogists were to occur, trendsin incidence would be affected. These events maybe especially true in the LM(M) classificationwhich shows least agreement between differentpathoiogists.'- The magnitude of this effect onthe rise of LM(M) observed in the present studyhas been assessed and is reported elsewhere.'^

Also, if melanoma were being reported at anearlier stage, a rise in relative proportions of earlyto advanced lesions would be observed. This is

the situation described here with respect tosuperficial sub-types: the majority of these had ameasured thickness of less Chan 0.75 mm (Fig. 1).Early reporting may arise when medicalpractitioners recognize lesions of which thepatient was unaware or about which he/she wasunperturbed; or when the general population isulert to suspicious pigmented lesions seen onthemselves or on others.

In the present study, the main characteristicsassociated with a patient's own observation of amalignant lesion, in contrast to having someother person draw attention to it, were thepatient's sex, and the histological type of thelesion. Women noticed a greaier proportion oftumours occurring on all siies except the upperlimb. Such a trend might reflect a positive aspectof social pressure on women to be appearance-conscious. With respect to type, nodularmelanomas were most often self-noticed, perhapsbecause these inherently invasive tumours maybe more likely to have associated symptoms suchas itching or bleeding.

In cases where the patient was unaware of alesion, melanomas on the back were detected insimilar proportions by doctors and lay persons.With respect to other sites more readily seen,doctors detected more lesions than did non-medical observers, except the limbs of males. Ifoverdiagnosis of the superficial types ofmelanoma by doctors were considered a possiblefactor in their rise, it is of interest that they firstsuspected only a quarter of SSM and a third ofLM(M) classes of lesion.

Thus, the findings of this study show that alarge proportion of the cases diagnosed in1979-80 were thin lesions of LM(M) and SSMtypes; and that the public in Queensland detecton themselves and on others more than two-thirds of the malignant melanomas diagnosed.

It is likely that education campaigns inQueensland have contributed to this publicawareness. Both the major organizationsinvolved, the Queensland Cancer Fund and theState Government's Division of Health Promo-tion testify to a dramatic rise in their educationprogrammes concerning all types of skin cancer,including melanoma, over the last decade.'*

CUTANEOUS MELANOMA IN QUEENSLAND 109

Information has been inereasingly disseminatedthrough leaflet publieations, through the media,particularly television, and through eourses forsehool students. This trend may be reasonablyrelated to the ability of people in Queensland todetect early eutaneous melanoma, althoughquantitation is not available.

In summary, it is difficult to distinguishbetween a true rise in disease which may haveoccurred, e.g. as the result of sun exposurereceived at increasingly popular beach resorts,and a rise resulting from early reporting in acommunity which is aware of the disease. Clearlylongitudinal studies are needed to documentthese trends in the future.

ACKNOWLEDGEMENTS

I am grateful to all pathoiogists in Queenslandwho contributed to the survey; and to Dr.Graeme Beardmore for his helpful criticism ofthe paper. The work was supported by theNational Health and Medical Research Councilof Australia and the Queensland Cancer Fund.

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Uensen, 0 . M. ana Bolander, A. M. (19S0r. "Trendsin Malignant Melanoma of ihe Skin", World HealthStatistics, 33: 2.

3 Little, J. H., Holt, J. and Davis, N. (1980); "ChangingEpidemiology of Malignant Melanoma inQueensland", Med. J. Aust., 1: 66.

' Arnistrong, B. K.. Holman. C. D. J.. Ford. J. M. andWoodings, T. L. U9821: "Trends in MelanomaIncidence and Mortality in Australia." In: Trends inCancer Ineidenee. Causes and practieat implications,K. Magnus, (ed.). Hemisphere Publishing Corp. NewYork. p. 399.

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* Breslow. A. (19701; "Thickness, Cross-sectional Area andDepth of Invasion in ihe Prognosis of CutaneousMelanoma",/imi. 5u/-^., 172:901.

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s McCarthy. W. H., Black, A. L. and Milton, G. W. (19S0):"Melanoma in New South Wales. An EpidemioiogicalSurvey 1970-1976". Cancer, 46: 927.

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'" Holman, C. D. J., Mulroney, C. D., and Armstrong, B. K.(1980): "Epidemiology of Pre-invasive and InvasiveMalignant Melanoma in Western Australia", Int. J.Cancer. 25' 117.

" McGovern, V. J., Shaw, H. M.. Milton. G. W. andFarago. G. A. (1980): "Is Malignant MelanomaArising in Hutchinson's Melanotic Freckle a SeparateDisease Entity?" Histopathotogy, 4: 235.

'̂ Larsen, T. E., Uule, J, H., OrelL S. R. and Prade, U.(1980): "Inlernationai Pathoiogists Congruence Surveyin Quantitation of Malignant Melanoma", Pathology,12: 245.

13 Green. A,, Little, J. H. and Weedon, D. "The Diagnosis ofHutchinson's MelanoUc Freckle (LenVigo Malignal inQueensland", Paihotony, (in press).

** Personal communications.