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Low incidence of cancer in the Sultanate of
Oman
Cervical cancer
"Early Cancer" vs. "Dormant Cancer" and the potential
hazards of the rush to surgery
Re: Cervical cancer
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| Umesh Kumar Dashora, Specialist, Diabetologist Ibri Regional Referral Hospital Send response to journal: Email Umesh Kumar Dashora: |
Low incidence of cancer in the
Sultanate of Oman
Cervical cancer screening is one of the many efforts at reducing the mortality and Morbidity associated with the cancer (1). A look into the epidemiological factors responsible for various cancers in different parts of the world may give new insight into prevention of cancer. Incidence rates (New cases /100,000 population) of different types of cancers vary widely from place to place. It was interesting to notice that almost all cancers in Oman have very low incidence rates (2) as compared to the USA. Here are the incidence rates of some cancers in Oman, compared to that of USA (as given in the manual of clinical oncology)(3) Lung cancer(2 Vs 66, colon (1.42 Vs .41), rectum and anal canal (1 Vs 16, female breast at the age of 50 years (2.4 Vs 150), uterine cervix (2.5 Vs 11), endometrium (1.32Vs 23), ovary (3.7 Vs 18), kidney and ureter (.65 Vs 11), urinary bladder (2 Vs 20), non-hodgkins lymphoma (2.78 Vs 15.3), skin cancer including malignant melanoma (2 Vs 281). Are there any special protective factors against cancers in Oman? Low prevalence of smoking and alcoholism, Low prevalence of HPV infection, practice of circumcision in male partners, multiparty and prolonged periods of lactation, dates (with their high fiber content) as the principal component of diet in Oman, poor industrialization, lack of pollution, predominantly rural habitat, low prevalence of HIV infection, very high temperature (precluding exposure to sun), along with traditional dresses which cover the whole body may be some of the factors maintaining the low incidence of cancers in Oman. Dr Murad Meena Faragale,MD.Jr Specialist Dr Umesh Kumar Dashora, MRCP.Specialist Dr Vandana Dashora, MD.Medical Officer Dr Samy suliman Marzook, MD.Specialist Dr Kamiran Dabbagh, MRCP.Sr Consultant and HOD Department of Medicine and Department of Gynaecology, Ibri Regional Referral Hospital, POB 46 PC 516 Sultanate of Oman Ph 968 491905 Ext 265 Fax 968 491915 E Mail: dashora@hotmail.com 1 Screening and mortality from cervical cancer Vaidya JS, Baum M Quinn MJ, Babb PJ, Jones JK, Adab P, McGhee S, and Hedley A. BMJ 1999;319 642. 2 Annual Statistical Report-1998.Directorate General of Planning.Ministry of Health, Sultanate of Oman.1999;10:53-56 3 Tabbarah HJ, Lowitz BB, Livingston RB, Lung cancer.In:Casciato DA, Lowitz BB (Eds).Manual of clinical oncology Boston.Little ,Brown and company 95.111-144 | |||
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| Peter O Yates
Send response to journal: Email Peter O Yates: |
EDITOR- In your letters (BMJ September 4, 99) headed "Screening and mortality from cervical cancer" I am surprised to find the diagnostic emphasis based on the presumption that this is a randomly occurring disease. As a student in 1940 I was taught that nuns (presumed at that time to be virgins) did not get this cancer. We now know, with lots of evidence, that cervical cancer is a venereal disease, the responsible herpes type virus being passed from female to female via male sexual partners. Why is there no comment about this in your letters and no statistics about the number of sexual contacts found in the various studies, which is clearly the most relevant fact in incidence and death from the condition.? Pathologists are struggling with difficult and often ambiguous smears to indicate a need for further treatment when the most obvious indicator, sexual promiscuity, is not even recorded. Peter O Yates | |||
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| Jayant S Vaidya
Send response to journal: Email Jayant S Vaidya: |
Dear Sir, We must constantly remind ourselves that mortality is the only valid endpoint for assessing a screening programme and any other surrogate can frequently give false answers. Quinn and colleagues (4 Sep, p 642-3) cannot provide an alternative explanation for the pattern of reduction of cervical cancer mortality but that cannot be used to refute our suggestion that screening might actually have slowed a natural reduction in cervical cancer mortality. There is a similar lack of explanation for the dramatic reduction in the incidence and mortality of invasive gastric cancers, which has occurred in the absence of a screening programme! On the other hand, we cannot ignore their paper and Adab's letter which suggests that despite reduction in incidence of invasive cervical cancer, the mortality has remained the same and also the recent letter from Sweden (3 July, p 55) that even breast cancer screening may not reduce mortality in the over 50 age group. These facts could actually point to a very fundamental hidden biological clue. Judah Folkman's has elegantly demonstrated that tumours cannot grow beyond 200 microns without stimulating their own blood supply. Thus many primary tumours can exist in a state of dynamic equilibrium and suppress the growth of their own secondaries by anti-angiogenic paracrine secretions1 Removal of the primary can provoke local angiogenesis from surgical trauma and release the secondaries from this inhibition and stimulate their growth. The paracrine secretion may be proportional to the tumour size until a critical level, when it can no longer continue to effectively inhibit the secondary growth. This critical size may be different for individual tumours and may well be above the clinical threshold. So there is really no meaning to the term 'early cancer'. We must realise that by the age of 60, every one of us harbours at least one of prostate, breast, thyroid or lung cancer in a sub-clinical (dormant) state- that is usually completely harmless 2-5. Effective treatment of cancer - and reduction in mortality from cancer in general will be possible only if we follow a strategy based on these principles. Once a primary cancer can no longer effectively inhibit its secondaries- it could be safely removed and its anti-angiogenic effect replaced and supplemented so that the secondaries remain suppressed. Removal of a primary cancer at an 'early' stage when it is effectively suppressing its secondaries, will only remove the inhibition of angiogenesis that will nullify any benefit from reduction of further metastasis. This could be elusive answer to the puzzle of the disappointments of screening. We should stop talking about "early cancer" and start thinking about "dormant cancer" and inappropriate "early surgery". Jayant S Vaidya Michael Baum Academic Department of Surgery, Royal Free and University College Medical School, University College London, 67-73 Riding House Street, London W1P 7LD References 1. Folkman J. Angiogenesis in cancer, vascular, rheumatoid and other disease. Nat.Med. 1995;1:27-31. 2. Whitmore WFJr. The natural history of prostate cancer. Cancer 1973;32:1104-1112. 3. Nielsen M, Thomsen JL, Primdahl S, Dyreborg U, Andersen JA. Breast cancer and atypia among young and middle-aged women: a study of 110 medicolegal autopsies. Br J Cancer 1987;56:814-819. 4. Harach HR, Franssila KO, Wasenius VM. Occult papillary carcinoma of the thyroid. A "normal" finding in Finland. A systematic autopsy study. Cancer 1985;56:531-538. 5. Vaidya JS, Baum M. Low-dose spiral computed tomography for lung-cancer screening. Lancet 1998;352:236; discussion 236-7 | |||
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| Kenneth Campbell, Clinical Information Officer Leukaemia Research Fund Send response to journal: Email Kenneth Campbell: |
Dear Sirs, Like Professor Yates I had, until recently, believed that nuns did not get cervical cancer. I accepted the received wisdom since I found it repeated so frequently. I realized how mistaken I was when I encountered the paper on this topic by Griffiths (1). In his paper Griffiths clearly and persausively demonstrates that the assertion that nuns are not at risk of cervical cancer is based on a mis-reading of Rigoni-Stern's original report of 1842 (2,3). I hope that if enough of us highlight Dr Griffiths' work often enough this myth will be laid to rest. Yours sincerely Kenneth Campbell, FIBMS This post is sent in a private capacity and does not necessarily reflect the views of my employer. 1. Griffiths M (1991) 'Nuns, virgins, and spinsters'. Rigoni-Stern and cervical cancer revisited. Br J Obstet Gynaecol 98, 797-802. The full text of this paper is available on the web at: www.obgyn.net/english/pubs/articles/nuns.htm 2. Rigoni-Stern (1842) Fatti statistici relativi alle malattic Cancerose. Giorn Prog Patol Terap 2, 507-517. 3. Rigoni-Stern (1987) Statistical Facts about Cancers on which Doctor Rigoni-Stern based his contribution to the Surgeons' Subgroup of the IV Congress of the Italian Scientists on 23rd September 1842 (Translation). Stat Med 6, 881-884. | |||
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