Sharp v Port Kembla RSL Club: establishing causation of laryngeal cancer by environmental tobacco smoke

To the Editor: Consensus exists that the provision of medical advice must be based on the correct interpretation of the evidence base. It is logical to assume that consideration should also apply to the provision of medical opinion in cases of medical litigation. The recent article on Sharp v Port Kembla RSL Club1 raises concerns which require wider debate.

It is not our purpose to discuss legal niceties nor to contest the epidemiological evidence of an increased incidence, in active smokers, of cancers at several sites, including the head and neck. Rather, we wish to concentrate on a central conclusion in the report, namely the assertion that ". . . a relationship between exposure to ETS [environmental tobacco smoke] and an increased risk of head and neck cancer . . . is supported by the available epidemiology".

The larger2 of the two studies quoted showed a crude odds ratio of 2.4 (95% CI, 0.9–6.8). This result is statistically non-significant. The authors also claimed a dose response between "moderate" and "heavy" exposure of 1.8 (95% CI, 0.5–7.3) and 4.3 (95% CI, 0.8–23.5) for non-smokers and 2.5 (95% CI, 0.9–6.9) and 5.3 (95% CI, 1.8–16.1) for smokers. Statistical interpretation of these results leads to a conclusion of no evidence of an increased risk compared with people who were "never" exposed to ETS.

Leaving aside our considerable reservations regarding the overall design and analysis of this case–control study, the data as presented are at best suggestive. Significant doubt must remain regarding the role of ETS in head and neck cancer.

That being so, two disturbing issues emerge which merit further debate.

Firstly, there is an ethical issue as to whether the requirements for the correct interpretation of the evidence base for medical opinion should be any different in the clinic or the courtroom.

Secondly, the judgment in this case highlights a dilemma in clinical practice. A clinician is not expected to practise according to non-significant differences in outcome. But, in the event of litigation, will the courts decide, as in this case, that bigger is better?