Japanese Journal of Clinical Oncology

Letters: Notes on Cancer Management from a Visiting Australian Researcher

To the Editor:

As an Australian researcher I recently had the opportunity to visit Tokyo for four days, made possible by support from the Foundation for Promotion of Cancer Research as an activity of the Australia-Japan Cancer Cooperative Research Program. The chief purpose of the visit was to attend the Twenty-Seventh International Symposium of the Princess Takamatsu Cancer Research Fund, entitled Fundamentals of Cancer Prevention. This was an outstanding forum in which scientists working at the forefront of the fields presented their recent data. The contributions covered a wide spectrum from laborotary investigations to clinical aspects of chemoprevention of cancer, with particular focus on experimental findings and possible molecular mechanisms involved. From an epidemiologist's point of view this was a valuable experience because it provided fine detail down to the cellular level, which complements data from human cancer prevention studies and can assist in their interpretation.

At the Symposium, it was evident that many of the scientific insights arose from the presentations, verbal and written, of Japanese scientists and delegates. In this way the full potential of such a meeting could be realized by building on comparisons between approaches used in various laboratories on one hand, and on contrasts in the genetic and cultural settings for cancer control on the other.

In this remarkable scientific setting I introduced the `Nambour Skin Cancer Prevention Trial: an Australian Field Trial' (Green et al., 1994) as a specific instance of an approach to cancer prevention which complemented, yet contrasted with, the experimental models of ultraviolet carcinogenesis and chemoprevention which were also presented. Ultraviolet radistion is, of course, a commonly exploited carcinogen in animal models universally, yet extrapolating from animals to humans without the benefit of human trial data would be extremely difficult with regard to findings of skin cancer chemoprevention studies. The Nambour Trial offers a paradigm of how pertinent human data can be gathered. This is possible because skin cancer is relatively common in Australians of European ancestry, though it is rare in Japan.

Briefly, this field trial has been conducted in an unselected adult population in Queensland, Australia, by a team of investigators funded by the Australian National Health and Medical Research Council. Using a factorial design, the main aims are to assess the value of routine application of sunscreen and of oral beta-carotene supplementation in reducing the incidence of basal and squamoua cell carcinomas and other sun-related skin disease. Participants were 1626 adult residents of Nambour, a sub-tropical Queensland township, who in 1992 were examined by dermatologists and then randomized to receive (or not) a standard high protection, broad-spectrum sunscreen (Auscreen Ultrablock Lotion SPF 15+, supplied by Woolworths Ltd) for daily application to all exposed sites on the head, neck, and upper limbs; and 30mg beta-carotene or placebo tablets (supplied by Roche Vitamins and Fine Chemicals) over 4V5 years. Occurrence of skin cancer was monitored by (i) the use of wallet-sized `treatment cards' carried by participants and completed by their doctors whenever a skin cancer was treated and (ii) skin examinations conducted by dermatologists in 1994, and again in August, 1996, prior to cessation of treatment. Knowledge of possible chemopreventive effects must await the assessment of incident skin cancer according to treatment group. In summary, while modest in size, and limited in the chemopreventive agents used, this Australian trial shows that skin cancer in a high risk population presents unusual opportunities for human chemopreventive trials to be carried out with cancer as an end-point, and with follow-up times which feasibly may be less than a decade.

Adèle Green
Senior Principal Research Fellow
Queensland Institute of Medical Research
Brisbane, Australia

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