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INCREASED RISK OF PROSTATE CANCER IN MEN
WHO WORK NIGHT SHIFTS
Professor David Neal, Professor of Surgical Oncology at Cambridge University and Clinical
Director of ProstateHealth UK reviews the research and how to manage the risks.
A number of recent publications have suggested that rates of
several types of cancer may be increased in people who work
irregular shifts, or those who work as flight attendants,
suggesting that rapid and irregular changes in body clock
may play a role in the development of certain cancers. The
mechanism by which such changes may occur are unclear, but
a commonly stated explanation involves alteration in the
levels of melatonin, a hormone produced in the brain which
normally peaks in the middle of the night. It has been
suggested that subsequent changes in the levels of hormones
controlled by the pituitary, a small gland in the brain, may
increase the risk of breast cancer for instance.
The International Agency for Research on Cancer recently
designated shift work that involves disruption of biological
rhythms, as a probable cause of human cancer (1, 2). The
evidence is strongest for breast cancer, where a systematic
review suggested that such occupational factors might
increase the risk by 50% (3) and where in Denmark
compensation is now payable to women who have worked
night shifts over a prolonged period.
Causes of prostate cancer
The causes of prostate cancer remain unclear, but commonly
accepted ones include ageing, family history (men who have
close male relatives affected by prostate cancer, particularly at
a young age), specific genetic factors such as the BRCA1 gene
and a western diet rich in red meat. There is also some
evidence that high levels of Vitamin D are protective of
prostate cancer (4, 5). There is agreement that environmental
factors, including dietary influences, are important and a high
intake of some vegetables including broccoli and tomatoes
may be protective.
Mutations in DNA are the underlying origin of all cancers,
and factors like inflammation may cause DNA damage by
production of reactive oxygen. One possibility is that certain
dietary factors may protect against this DNA damage by the
production of proteins which “mop up” the harmful reactive
oxygen.
Night working and prostate cancer
A recent study of over 3,000 men who regularly carried out
night work showed a significantly increased risk for lung,
prostate, bladder and colon cancer (6). Clearly some
additional factors such as cigarette smoking might be more
common in night workers, but are unlikely to explain the
doubling of risk for prostate cancer which was found in this
study. Two other studies found an increase in prostate cancer
in night workers (7, 8), and one did not (9). The incidence of
prostate cancer is strongly related to awareness of the
condition and national screening programmes for prostate
cancer based on testing for Prostate Specific Antigen (PSA).
However, the evidence is now growing that working at night
for prolonged periods may significantly increase the risk of
prostate cancer.
Early detection of prostate cancer using PSA testing alone
remains controversial because although it decreases death
from the disease, it also diagnoses many cancers which would
not otherwise have been detected and it risks “overtreatment” for such cancers. One way to reduce the number
of negative biopsies consequent on PSA testing is to use a new
biomarker, human glandular kallikrein 2 (hK2) which, when
used with a combination of total, free and intact Prostate
Specific Antigen (iPSA), has been shown in studies to
considerably reduce the number of unnecessary biopsies in
patients with an abnormal PSA test result by up to 50%. (10)
The use of this panel of 4 biomarkers is thus a more accurate
method for the detection of prostate cancer. Men with early
stage prostate cancer often have no specific symptoms, men
with faster growing prostate cancer can benefit from early
detection.
Early detection of any cancer is more effective when targeted
at those with an increased risk of developing that cancer.
There is now growing evidence that night workers may
represent such a group, although more research needs to be
done. Such men may benefit from increased awareness and
information about the pros and cons of early detection of
prostate cancer.
References
1. Straif K, Baan R, Grosse Y, et al. Carcinogenicity of
shiftwork, painting, and fire-fighting. Lancet Oncol.
2007;8(12):1065–1066.
2. International Agency for Research on Cancer. Painting,
Fire-Fighting and Shiftwork. (IARC Monographs on the
Evaluation of Carcinogenic Risks to Humans, vol 98).
Lyon, France: International Agency for Research on
Cancer; 2010.
3. Night work and breast cancer risk: a systematic review and
meta-analysis. Megdal SP, Kroenke CH, Laden F, Pukkala
E, Schernhammer ES. Eur J Cancer 2005; 41(13): 2023-2032.
4. Gilbert R, Metcalfe C, Fraser WD, Donovan J, Hamdy F,
Neal DE, et al. Associations of circulating 25hydroxyvitamin D with prostate cancer diagnosis, stage
and grade. Int J Cancer. 2012 Sep 1;131(5):1187-96.
5. Gilbert R, Martin RM, Fraser WD, Lewis S, Donovan J,
Hamdy F, et al. Predictors of 25-hydroxyvitamin D and its
association with risk factors for prostate cancer: evidence
from the Prostate testing for cancer and Treatment study.
Cancer Causes Control. 2012 Apr;23(4):575-88.
6. Parent ME, El-Zein M, Rousseau MC, Pintos J , and
Siemiatycki J. Night Work and the Risk of Cancer Among
Men. American Journal of Epidemiology. 2012. DOI:
10.1093/aje/kws318
7. Kubo T, Ozasa K, Mikami K, et al. Prospective cohort study
of the risk of prostate cancer among rotating-shift workers:
findings from the Japan Collaborative Cohort Study. Am J
Epidemiol. 2006;164(6):549–555.
8. Conlon M, Lightfoot N, Kreiger N. Rotating shift work and
risk of prostate cancer. Epidemiology. 2007;18(1): 182–183.
9. Schwartzbaum J, Ahlbom A, Feychting M. Cohort study of
cancer risk among male and female shift workers. ScandJ
Work Environ Health. 2007;33(5):336–343.
10. Vickers, A.J., et al., A four-kallikrein panel predicts prostate
cancer in men with recent screening: data from the
European Randomized Study of Screening for Prostate
Cancer, Rotterdam. Clin Cancer Res, 2010. 16 (12): p. 3232-9
RISK MANAGEMENT FOR NIGHT SHIFT EMPLOYEES - PROSTATECHECK
1. Education and information on the pros and cons of PSA testing and early detection.
2. Prostate cancer risk assessment based on lifestyle, symptoms and family history
3. Blood test giving unique feedback on 4 biomarkers including PSA
If employee is moderate or high risk consider:
(a) Informing existing employees of the additional risk of prostate cancer and advising new employees that they may be
taking on an unnecessary risk as night shift personnel.
(b) Asking employee to sign waiver saying they understand and accept the additional risk.
(c) Consider employee for alternative role.
HealthScreen UK
Contact: John Picken, Managing Director, HealthScreen UK [email protected] t: 01223 492188 or 0845 450 5603
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