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Mortality and Morbidity: Cancer trends
While there has been a decrease in cancer deaths since 1985, the cancer incidence rate increased between 1985 and 2000. In 1985, there were 392 new cases of cancer diagnosed per 100,000 population. A high incidence of prostate cancer among men, combined with slightly higher rates for breast and ovarian cancer, contributed to an overall peak in cancer incidence in 1994, when 478 new cases per 100,000 population were diagnosed. Cancer incidence then fell to a rate of 451 in 2000.
Cancer incidence among men increased from 481 new cases per 100,000 men in 1985, to a peak of 608 in 1994, declining to 536 per 100,000 in 2000. The peak in 1994 occurred around the time when there was a peak in the number of men tested using the prostate specific antigen (PSA) test (SEE ENDNOTE 3). This test identified prostate cancers that previously may not have been diagnosed through other tests or the presence of symptoms (SEE ENDNOTE 4).
Women consistently had lower cancer incidence rates than men. In 2000, the cancer incidence rate for women was around 70% of the rate for men. Although the relative growth in cancer incidence was higher among women than men between 1985 and 2000, the increase was more steady over the period.
Cancer incidence is lowest in late childhood and increases with age.(SEE END N0TE 2) The most common forms of cancer among children aged 0-14 years are lymphatic leukaemia, and brain and central nervous system cancers, which together accounted for 51% of cancer incidence in this age group in 2000. For almost all cancers, incidence is higher among boys than among girls (SEE ENDNOTE 5).
Of the seven priority cancers for which data are routinely collected, the incidence of lung cancer among men, and cervical cancer among women, decreased between 1985 and 2000. There was an increase in the incidence of prostate and colorectal cancer among men; lung and breast cancer among women; and melanoma skin cancer and non-Hodgkin's lymphoma for both men and women.
While changes in the incidence rates for specific cancers may reflect more, or fewer, people developing a type of cancer, they may also relate to medical advances that improve detection and identification of the site of origin of cancer in the body. For example, the increased incidence of prostate cancer has been largely attributed to the PSA test, which increased detection and reporting of latent prostate cancers.3 Conversely, the halving of the incidence rate for cervical cancer between 1985 and 2000 (from 15 new cases per 100,000 women to 8) may be partly due to a national cervical screening program introduced in the early 1990s.2 Cervical cancer is one of the most preventable and curable of all cancers - up to 90% of cases of the most common type of cervical cancer can be prevented if cell changes are detected and treated early (SEE ENDNOTE 7). Thus screening, which encouraged women to have regular Pap smear tests, supported more effective control of this cancer (see Australian Social Trends 2004, How women care for their health, pp. 77-81).
Smoking is associated with an increased risk of developing many diseases including lung cancer. In 2001, 24% of the adult population were current smokers, a decrease since 1989-90 when 28% smoked. Smoking rates were consistently higher among men (see Australian Social Trends 2003, Health risk factors among adults, pp 74-78). In keeping with this, the rate of incidence of lung cancer was also higher among men. However, the gap between men and women is closing, with the incidence of lung cancer declining among men (from 81 new cases per 100,000 men in 1985, to 62 in 2000) but increasing among women (from 19 to 27). As there is a time lag between exposure to the carcinogenic agents of tobacco and the onset of cancer, this increase reflects smoking patterns of around twenty years ago, when the proportion of female smokers increased relative to male smokers.
Data on non-melanocytic skin cancers are not routinely collected by state and territory cancer registries, and instead, estimates are provided by periodic national surveys. It is estimated that there were 374,000 new cases of non-melanocytic skin cancer diagnosed in 2002 (SEE ENDNOTE 8).
Measuring the chance of survival for people diagnosed with cancer, relative to people without cancer, assists in assessing the broad impacts of early detection methods such as screening, and the efficacy of treatment. The chances of surviving at least five years after diagnosis with any type of registrable cancer improved considerably between 1982-1986 and 1992-1997, from 49% to 60% (if deaths from other causes are excluded).
There were improvements in survival ratios for the priority cancers, with prostate cancer showing the greatest relative improvement (about 40%). That is, while there was an increase in the incidence of prostate cancer, there was not an equal increase in mortality. The introduction of PSA testing, combined with the tendency for prostate cancer to have slow, non-life threatening growth, and affect mainly older men, could partly explain the increase in survival ratio between 1987-1991 and 1992-1997 (SEE ENDNOTE 3, ENDNOTE 9, ENDNOTE 10). However, factors other than PSA testing may be involved (SEE ENDNOTE 3, ENDNOTE 11).
Relative improvement in the survival ratio for breast cancer was similar to that for colorectal cancer (about 15%), although the survival ratio for colorectal cancer was lower. Earlier detection and diagnosis, and improved treatments are likely to have increased the chances of surviving such cancers.
The likelihood of surviving for five or more years after being diagnosed with lung cancer also improved between the 1980s and the 1990s (from 10% to 12%). That said, lung cancer remained the cancer with by far the lowest likelihood of survival of all of the selected priority cancers.
The death rate for a specific cancer is influenced both by how commonly it occurs, and by how likely people are to survive it. For example, although non-melanocytic skin cancers are the most commonly diagnosed cancer in Australia, relatively few people die of this cancer if treated early. Death rates from cancer declined for both men and women between 1985 and 2002, although men continued to experience a higher rate of death from cancer than women.
Childhood cancer is relatively uncommon (children aged 0-14 years made up less than 1% of all cancer patients in each year from 1983 to 2000).5 However, cancer is a leading cause of death among children aged 1-14 years (118 children in this age group died from cancer in 2002). Death rates for children improved from four deaths per 100,000 children aged 0-14 years in 1993, to three per 100,000 in 2000, reflecting advances in various cancer treatments (SEE ENDNOTE 6).
Of all the priority cancers, lung cancer has consistently been the leading cause of death for men since the early 1950s (SEE ENDNOTE 12). However, as with incidence rates for lung cancer, the difference between men and women is reducing slightly. Female death rates for lung cancer increased between 1985 and 2002, from 17 deaths per 100,000 women to 24, while the male death rate decreased from 77 deaths per 100,000 men to 53.
In 1985, there were 36 deaths per 100,000 men as a result of prostate cancer. While there were substantial improvements in the likelihood of surviving prostate cancer between 1985 and 2002, the death rate for this condition stayed much the same over this period (36 deaths per 100,000 men in 2002).
For women, there was a decrease in deaths due to colorectal cancer between 1985 and 2002 (from 28 to 20 deaths per 100,000 women). The incidence rate for colorectal cancer remained relatively steady over the period (around 53 new cases per 100,000 women each year), so the reduction in deaths may be due to increased chance of survival.
The slight improvement in the survival ratio for cervical cancer combined with the improved ability to prevent cervical cancer through effective screening, resulted in mortality decreasing by more than half.
While the incidence of breast cancer in females increased between 1985 and 2000, the death rates decreased (from 31 to 25 deaths per 100,000 women). This may be attributed to earlier detection and/or improvements in treatment leading to a better chance of surviving the disease for longer.
YEARS OF LIFE LOST THROUGH CANCER
In 2002, the years of potential life lost through cancer deaths amounted to 189,562 for men and 156,522 for women. For a specific cancer, the number of years of potential life lost reflects not only the incidence and survival rates for that cancer, but the age at which deaths from that cancer commonly occur. For example, although the death rate for non-Hodgkin's lymphoma was higher than for melanoma skin cancer, slightly more years of potential life were lost due to the latter. This indicates that melanoma skin cancer affects people earlier in life, resulting in more premature deaths.
Although death rates due to prostate cancer were the second highest of all the priority cancers in men, this type of cancer resulted in a comparatively low number of years of potential life lost, as it mainly afflicts older men. While a similar number of women died from breast cancer as died from lung cancer in 2002, there were more years of potential life lost through breast cancer (36,684 years) than through lung cancer (22,909), as women with breast cancer are more likely to die at a younger age than women with lung cancer.
1 Commonwealth Department of Health and Ageing, <http:// www.health.gov.au/pq/nhpa>, accessed 23 April 2004.
2 Australian Institute of Health and Welfare (AIHW) 2002, Australia’s Health 2002, AIHW Cat. No. AUS 25, Canberra.
3 Smith, DP and Armstrong, BK, ‘Prostate-specific antigen testing in Australia and association with prostate cancer incidence in New South Wales’, The Medical Journal of Australia, 1998, vol. 169, pp. 17-20, <http://www.mja.com.au>, accessed 3 March 2004.
4 Commonwealth Department of Health and Ageing,<http://www.health.gov.au/pubs/ahtac/prostate.htm>, accessed 20 October 2003.
5 Australian Institute of Health and Welfare 2002, Australia's Children: Their Health and Wellbeing 2002, AIHW Cat. No. PHE 36, Canberra.
6 Australian Institute of Health and Welfare and Australasian Association of Cancer Registries 2002, Cancer in Australia 1999, AIHW Cat. No. CAN 15, Canberra.
7 Commonwealth Department of Health and Ageing,<http://www.cervicalscreen.health.gov.au/papsmear/what.html>, accessed 3 November 2003.
8 National Cancer Control Initiative, <http://www.ncci.org.au/pdf/NMSCreport.pdf>, accessed 5 April 2004.
9 Stricker, PD and Eisinger, DR, ‘Patient preference and prostate cancer screening’, The Medical Journal of Australia 1997, vol. 167, pp.240-241 <http://www.mja.com.au/>, accessed 3 March 2004.
10 Australian Institute of Health and Welfare and Australasian Association of Cancer Registries 2003, Cancer in Australia 2000, AIHW Cat. No. CAN 15, Canberra.
11 Australian Institute of Health and Welfare, Cancer Survival in Australia, 2001 Part 1: National Summary Statistics, Cancer Series No. 18, 2001, AIHW Cat. No. CAN-13.
12 Australian Institute of Health and Welfare, <http://www.aihw.gov.au/Interactive cancer data/Cancer age standardised data cube>, accessed 3 March 2004.
13 Australian Bureau of Statistics (ABS) and Australian Institute of Health and Welfare (AIHW) 2003, The Health and Welfare of Australia's Aboriginal and Torres Strait Islander Peoples, 2003, ABS cat. no. 4704.0; AIHW Cat. No. IHW-11, ABS Canberra.
14 Coory, MJ, Thompson, A and Ganguly, I 2000, 'Cancer among people living in rural and remote Indigenous communities in Queensland', Medical Journal of Australia, vol. 173, no. 6, pp. 301-304.
15 Coory, M, Fagan, P, Muller, J and Dunn, N 2002, 'Participation in cervical cancer screening by women in rural and remote Aboriginal and Torres Strait Islander communities in Queensland', Medical Journal of Australia, vol. 177, no. 10, pp. 544-547.