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THE Lancet Oncology Commission on the expanding role of primary care in cancer highlights the rising incidence of cancer worldwide:
In Australia, cancer incidence is estimated to increase by 40% from 2007 to 2020 with approximately 150 000 new cases diagnosed annually by the end of this decade. This is mainly due to an ageing and increasing population in Australia.
While there have already been significant improvements in cancer survival resulting from more effective treatments, international policy is placing greater emphasis on cancer awareness, cancer screening and early diagnosis of symptomatic disease to further improve outcomes.
The growing number of cancer survivors has also led to the recognition that primary care must play a greater role in cancer control across the continuum of care, from prevention and early detection to survivorship and palliative care.
A GP with 2000 patients will see approximately 6‒8 new cases of cancer per year, similar to the incidence of diabetes. They would also have roughly 70 cancer survivors among their patients, a number predicted to double by 2040.
In comparison, a GP with 2000 patients would have about 120 patients with diabetes. This is the context for this significant publication by The Lancet Oncology.
The general practice team can make significant contributions to improving participation rates in cancer screening. This is especially important as the National Bowel Cancer Screening Program becomes a fully biennial program, with current participation rates only at 36%.
There is level I evidence that audit and feedback, computerised reminders and GP endorsement letters sent to patients in advance of the screening program invitation can all increase participation rates.
Cancer screening participation rates will be a key performance indicator for the newly formed Primary Health Networks so they will need to support practices to implement this evidence.
Even in countries where there are national screening programs, about 85% of patients with cancer present symptomatically to primary care.
While the GP plays a key role in early recognition of cancer, this is challenging because the symptoms of cancer overlap with more common benign causes. In most cases where a GP might reasonably suspect cancer, the patient will in fact have a benign condition.
For several cancers, growing evidence shows that early diagnosis of symptomatic disease is associated with improved clinical outcomes. Prevention of avoidable delays in primary care by accurate assessment of the likelihood of cancer, and acceleration of the diagnostic process, could therefore contribute to improvements in cancer survival.
In the past 10 years, our understanding of how cancer presents in general practice has improved substantially so we now have validated risk models that predict the likelihood of cancer based on the pattern of symptoms, signs and routine blood tests. These risk models could be used in general practice, for example, through computer decision support systems, to help GPs identify patients who may require more urgent investigation for possible cancer.
The Lancet Oncology Commission and associated editorials emphasise the importance of improving the integration of cancer care across the cancer continuum. In the context of early symptomatic diagnosis, this means the establishment of clear referral pathways for patients with symptoms suggestive of cancer.
There is good evidence from the English NHS 2-week wait diagnostic pathways that these can reduce the time to diagnosis for a large proportion of cancer patients, and that greater use by GPs of these rapid access pathways is associated with lower cancer mortality.
Nonetheless, there are probably certain cancer types, such as myeloma and pancreatic cancer, that are inherently more difficult to diagnose in primary care because of their non-specific symptom profiles. Early diagnosis of these cancers could depend on the identification of accurate biomarkers that could be used in populations at high cancer risk.
Until then, heightened awareness of key symptoms and signs, and application of best epidemiological evidence on how they predict cancer risk remain at the heart of early diagnosis of cancer in primary care.
Professor Jon Emery is the Herman Professor of Primary Care Cancer Research at the department of general practice, University of Melbourne. Professor Emery was an author on The Lancet Oncology Commission on the expanding role of primary care in cancer control.
In an accompanying article in this issue of MJA InSight, Professor Geoff Mitchell, professor of general practice and palliative care at the University of Queensland, discusses the role of GPs in the care of patients with cancer at the end of life.
This week’s MJA features a series of articles on cancer.
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Professor Emery sounds a very timely note about the importance of primary care in cancer control. As he makes clear, the numbers of people being diagnosed with cancer are rising in Australia due to the combined forces of an aging population and increasing population size. However, a third force is also operating, at least for cancers at some sites – namely, higher age-specific cancer rates. Research published this year in the Australia New Zealand Journal of Public Health estimated that up to 1 in 3 cancers diagnosed in Australia in 2010 was attributable to modifiable exposures. In other words, up to one-third of cancers in Australia are potentially preventable by modifying our lifestyle. The chief exposures contributing to the excess burden of cancer in 2010 were tobacco smoke, solar UV radiation, dietary factors (excess red meat, insufficient fibre, insufficient fruit and vegetables), obesity, alcohol, insufficient physical activity and exposure to infections known to cause cancer (primarily HPV, H pylori, HBC, HCV). The opportunities for preventing cancer by reducing exposure to these factors are enormous. Primary care practitioners are at the front-line for monitoring patients for ‘risky’ factors, and encouraging adoption of healthier lifestyles, in addition to their role in promoting screening and early detection of cancers.