physician who wishes to prescribe promazine hydrochloride, promethazine hydrochloride, or promethazine theoclate for his patients, and be sure they get them, should always prescribe sparine, phenergan, or avomine. A. R. M. FREEMAN. CANCER INCIDENCE OF THE AFRICAN POPULATION OF KYADONDO
SIR,-Dr. Davies and others (Aug. 18) show that up to the age of about 50 the age-specific cancer mortality-rates in Kyadondo (Africa) are comparable with those in Norway. They draw attention to the fact that beyond this age, cancer-rates increase rapidly with advancing age in Norway, whereas in Kyadondo they level off, or even decrease in females. They suggest that environmental carcinogens in industralised countries are responsible for the steep rise of cancer-rates with age; they add the important and optimistic corollary that, in theory, a vast amount of cancer in the older age-groups is preventable. This argument does not lack circumstantial support, but it may not represent the whole truth.
Fig. 2-Photo-X-ray of hand.
the standard radiograph of the hand. The details of bone structure has proved as good
reproduction of as
radiographs. Satisfactory films for bone measurements have been obtained from the three methods using the following technical factors:
The bone definition which can be produced by photo-X-ray and polaroid methods is shown in the accompanying figures. Departments of Physical Medicine and Radiology,
University of Alberta Hospital, Edmonton, Canada.
J. G. PARISH H. E. DUGGAN.
NAMING OF DRUGS SIR,-In a recent authoritative article1 on obstetric analgesia Mr. Hawksworth recommends the use of ’ Pethilorfan’ (pethidine and levallorphan) with promethazine. Reference to the British National Formulary (1960, Alternative Edition) shows that two drugs with the word promethazine in their names are listed, promethazine hydrochloride (’ Phenergan ’) and promethazine theoclate (’Avomine’), but the accompanying text uses the name promethazine alternatively for and apparently synonymously with promethazine hydrochloride. That this can cause confusion is easily shown by turning to the index (p. 286), where promethazine and promethazine hydrochloride are listed one after the other as though they were different drugs. In addition to this source of confusion it may be noted that the drug listed immediately before promethazine is promazine hydrochloride (’ Sparine ’). While it is desirable that approved names rather than proprietary ones should be used in prescribing in the interests of scientific accuracy and also of economy in prescribing, the interests of the patient should remain paramount. I suggest that while the approved names remain as similar as they now are, the 1. Hawksworth, W. Practitioner, 1962, 189, 169.
Their conclusion would be more convincing if mortality from non-malignant disease in Kyadondo above the age of 45 were not so high; this raises the possibility that a precancerous condition could predispose to death from diseases endemic in African populations. A competitive situation of this kind has been proposed by Stewart1 to account for an inverse correlation between pneumonia and leukxmia mortality in children. Similarly, the large increase of leuksemia mortality in adults (especially chronic lymphatic leukxmia)2 in this country during recent decades may plausibly be attributed in part, at least, to the diminishing lethality of infectious diseases through the use of sulphonamides and antibiotics, improved medical care, and better dietary and living standards.l By the same token, the virtual absence of chronic lymphatic leukaemia in Japan and other Asiatic countries could be ascribed to a high competitive incidence of infectious and parasitic disease. To rationalise, 3 a given inheritance will predispose to certain types of leukxmia,3 but it will also weaken the immune defence mechanism, and in an environment with a high level of infective and parasitic agents death from the latter will tend to supervene. A competitive relationship between an infective or parasitic agent and other precancerous conditions is more difficult to
comprehend. Nevertheless, many cancers, particularly of epithelial tissue, seem to originate in areas where there is an histologically recognisable premalignant change.44 I have recently argued3 that hyperplasia of certain premalignant cells and a multicentric cancer origin are probable whenever the (corrected) age-specific cancer incidence-rate is proportional to a power of adult age appreciably higher than three. This property is displayed by most, if not all, epithelial tumours,5 and is also observed ’in post-1955 mortality statistics for chronic lymphatic leukaemia (although, interestingly enough, not for other types 2). Should this hyperplasia of premalignant cells be associated with a vulnerability to certain nonmalignant diseases, it would provide a supplementary explanation of the observations of Davies and his coworkers. According to my model,3 premalignant hyperplastic cells in a given clone will, for many tissues, increase in number with the cube of time; but, on the average, the number will not become significantly greater than unity
until an age of about 40 and above is attained. This is the age-range (allowing for the latent period) in which cancer mortality in African populations begins to diverge from 1. Stewart, A. Brit. med. J. 1961, i, 452. 2. Court Brown, W. M., Doll, R. ibid. 1959, i, 1063. 3. Burch, P. R. J. Nature, Lond. 1962, 195, 241. 4. Willis, R. A. Pathology of Tumours. London, 1960. 5. Armitage, R., Doll. R. Brit. J. Cancer, 1954, 8, 1.