Table 1

Model estimates, sensitivity values and sources

Base model valuesValues in one-way sensitivity analysesParameters for probabilistic sensitivity analyses*Sources
Base estimateLow estimateHigh estimateDistribution type and values
Duration of the model30 years10 years40 yearsn/an/a
Starting age of cohort50 years3060Normal (mean 50, SD 9)n/a
Probabilities (Annual)
Person developing benign lesions0.38320.29110.4753Beta (n=107, r=41)†Janda et al, Control group16
Person developing multiple benign lesions0.50640.4280.5849Darlington et al24, Streeton et al31
Person developing keratinocyte cancersAge-dependent tableTable (see online supplementary file), for example, 39 years=0.0180, 79 years=0.0709Pandeya et al22
Person developing multiple keratinocyte cancersAge-dependent tablePandeya et al22
Person developing melanomaAge-dependent tableTable (see online supplementary file), for example, age 44 years=0.0006, 79 years=0.0029Qld Cancer Statistics On-Line (av 2011–2015)18
Person developing multiple melanomas0.0070.0060.009Youlden et al26
Those with melanoma have an invasive thin melanoma in general population (0<1 mm)0.2820.260.30Beta (n=97 114, r=27 386)†Aitken et al23 (remainder of thick and thin have in situ)
Those with melanoma have thicker melanoma in general population (>1 mm)0.270.250.29Beta (n=97 114, r=26 221)†Aitken et al23
Those with melanoma have thicker melanoma (>1 mm) with whole body clinical skin examination (early detection)0.250.210.29Beta (n=97 114, r=24 747)†18% reduction in thick melanoma over 3 years Aitken et al,23 applied to Aitken et al6
Undetected melanomas0.231Beta (α=33.94, β=112.93)Aitken et al21
Undetected KCs0.138Beta (α=38.17, β=238.39)Aitken et al21
Undetected benign lesions0.395Beta (α=26.49, β=40.57)Aitken et al21
Undetected tumour being detected0.200.150.25Beta (α=35.36, β=141.42)Assumption
Death from melanoma if ≤1 mm (thin) by age5 year=0.02
10 year=0.05
Weighted by tumour size categories, Gershenwald et al8 (see online supplementary file)
Death from melanoma if >1 mm (thicker)5 year=0.233
10 year=0.301
See above
Mortality in Queensland general populationAge-dependent tableAustralian Bureau of Statistics, Life tables, 2015–2017, Qld population, Table 1.920
Rate ratios
Rate ratio for KCs and melanomas found during early detection1.501.401.60Gamma (α=44.4, λ=29.63)Janda (2014), 60% skin malignancies versus 40% in control—so 50% increase in skin cancers found16
Rate ratio of melanoma in sunscreen users0.500.450.55Beta (α=312, β=312)Green et al, invasive and non-invasive melanomas4
Rate ratio of KCs in daily sunscreen users0.650.450.94Beta (α=14.91, β=8.03)Van der Pols et al, 1993–2004 follow-up, persons affected, applied rate for squamous cell carcinomas5
Rate reduction of benign lesions in daily sunscreen users0.760.660.86Beta (α=9.91, β=3.13)Darlington et al,24 24% rate reduction in actinic keratoses
Rate of undetected skin tumours being detected annually0.200.150.25Beta (α=35.36, β=141.42)Assumption
Health utilities (quality of life)
Benign lesions and being lesion free1.00Assumption
Having keratinocyte cancers0.980.950.99Beta (α=5.21, β=0.09)Seidler et al30
Disutility of each subsequent KC or benign lesion treated−0.03−0.04−0.02Seidler et al30 used disutility for KC recurrence
In situ or thin melanoma (≤1 mm)0.970.90.98Beta (α=0.28, β=0.009)Tran et al28 meta-analysis
Thicker melanoma (>1 mm)0.770.70.83Beta (α=5.29, β=1.58)Tran et al28 meta-analysis
Costs (US$)
Sunscreen in high users (per year)13.59.517.6Gamma (α=44.4, λ=2.28)Retail supermarket brand, 50+SPF sunscreen 500 mL @AU$6.50 each, 3 bottles each year
Sunscreen in low users (per year)4.53.25.9Gamma (α=44.4, λ=6.84)As above, 1 bottle used every 3 years
Clinical whole body skin examination—higher use in early detection78.3338.59117.50Gamma (α=44.4, λ=2.28)Standard GP consultation, MBS item 23 plus patient out of pocket fees
Clinical whole body skin examination—lower use in primary prevention and no intervention13.06039.17Gamma (α=44.4, λ=6.84)As above, 1 per 3 years
Diagnose and treat a benign lesion115.580.8150.1Gamma (α=44.4, λ=0.42)Streeton 2006 for treatment types and Medicare items
Treating first KC218.9186.1251.1Gamma (α=44.4, λ=0.14)Gordon et al,25 mean cost
Treating multiple KCs414.0351.9476.1Gamma (α=44.4, λ=0.08)Gordon et al,25 mean cost
Thick melanoma in first year22 607.016 524.930 689.1Gamma (α=44.4, λ=0.001)Elliott et al46 Weighted by tumour size
Thick melanoma after year 1Time dependent tableElliott et al,46 AU$7262 for 2 years weighted by tumour size, AU$1275 thereafter
In situ and thin melanoma in first year1189.5832.71546.4Gamma (α=44.4, λ=0.03)Elliott et al46
In situ and thin melanoma after year 1115.50.00.0Elliott et al,46 constant cost of follow-up
Care for person in last months of life16 591.111 613.821 568.5Reeve et al47 (death from other causes)
Death from thicker melanoma (>1 mm)23 662.816 563.930 761.6Reeve et al47 (death from cancer)
Premature death from melanoma—productivity losses207 794.6176 625.4238 963.8Carter et al17 (applies to persons aged <65 years)
  • *It was necessary to have beta distributions for rate ratios under one and gamma distributions for those over one because log normal distributions created excessive variation and created problems with coherence with branch probabilities.

  • †Rather than alpha and beta parameters, we used the n and r directly here from the study which is an option allowed in TreeAge. α=r, β=nr.

  • GP, general practitioner; KC, keratinocyte cancer; MBS, Medicare Benefits Scheme; SPF, sun protection factor.