A critical analysis of reasons for improved survival from invasive cutaneous melanoma Colin Glen Luke 1 , Brendon John Coventry 2 , Erwin Joseph Foster-Smith 3 & David Murray Roder 4 * 1 Epidemiology Branch, Department of Human Services, South Australia; 2 Adelaide Melanoma Unit, Department of Surgery, University of Adelaide, Royal Adelaide Hospital; 3 Department of Tissue Pathology, Institute of Medical and Veterinary Science; 4 The Cancer Council South Australia, Centre for Cancer Control Research, P.O Box 929, 5061 Unley, South Australia Received 6 January 2003; accepted in revised form 28 July 2003 Key words: cutaneous melanoma, level, survival, thickness, tumour biology. Abstract Objective: To determine the extent to which increases in survival from melanoma are explained by changes in thickness, level, histological type, site of lesion, and sociodemographic characteristics. Methods: Analyses of changes in survival among 9519 South Australians with melanoma reported to the State’s population-based cancer registry during the 1980–2000 diagnostic period, using proportional hazards regression to adjust for thickness, level and other characteristics. Results: Lower survivals applied for thicker lesions, deeper Clark levels, lesions on the trunk and scalp/neck, and for older cases and males. After adjusting for these characteristics, the relative risk (95% confidence limits) of case fatality for the 1994–2000 diagnostic period was 0.79 (0.63, 0.99), when compared with the 1980–1986 baseline. Prior to adjusting, the relative risk for these cases was 0.58 (0.47, 0.72). An unexpected finding was a secular change for deeper Clark levels within Breslow thickness categories. Conclusions: Approximately half the survival increase was not explained by changes in thickness, level, lesion site, and age and sex. Other possible contributors warranting further study include changes in ulceration, nodal or more distant site involvement, treatment gains and changes in tumour biology. The trend for deeper Clark levels within Breslow thickness categories requires independent confirmation. Introduction Pronounced increases in age-standardized incidence of invasive cutaneous melanoma have been recorded in many populations of predominantly European extrac- tion [1–4]. Often commensurate increases in mortality have not been observed, such that incidence and mortality rates have diverged, particularly in the young- er age groups [1]. In South Australia, the age–sex standardized incidence, for all ages combined, increased by 90% between 1977–1981 and 1997–2000, whereas the mortality rate remained stable, despite an earlier three- fold increase between the early 1950s and 1977 [5, 6]. A likely reason cited for the divergence in melanoma incidence and mortality has been increased case survival [1]. In South Australia, 5-year survivals from invasive melanoma increased from 87% for the 1977–1983 diagnostic period to 89% for 1984–1990 and 93% for 1991–1998 [7]. Upward trends of a similar magnitude have been reported elsewhere in Australia and in North America [2, 8]. Earlier diagnosis probably accounts for much of these survival increases [1]. In South Australia, where survival has been shown to vary markedly with thickness of lesion at diagnosis [9], the percentage of invasive lesions diagnosed with a thickness of 0.75 mm or less increased from 40% in 1980–1983 to 57% in 1996–2000 [5]. This occurred at a time of active promotion of early detection, particularly among high-risk groups [10]. Meanwhile, it is evident that surgical management has become more conservative, without a detectable increase * Address correspondence to: David Roder, The Cancer Council South Australia, P.O. Box 929, 5061 Unley, South Australia. Ph.: +61-8-8291-4103; Fax: +61-8-8291-4268; E-mail: roder@chari- ot.net.au Cancer Causes and Control 14: 871–878, 2003. 871 Ó 2003 Kluwer Academic Publishers. Printed in the Netherlands.