Clinical Oncology SC014: The War Against Cancer Flashcards
Global burden of cancer
2018:
- 18.1 million new cases
- 9.6 million deaths
—> Projected 29 million new cases in 2040
Sustainable development goals (SDGs) set by UN in 2015:
- ↓ 1/3 premature death from NCD through prevention + treatment
—> Cancer, CVS, Respiratory disease
WHO:
- ↓ 25% premature death by 2025
—> by ↓ risk factors
Comprehensive cancer control strategy + action plan:
- Prevention
- Early detection
- Diagnosis + Treatment
- Palliative care + Survivorship
Cancer burden in HK
Total no. of new cases: 34028
Total no. of deaths: 14209 (31% of all deaths: Top killer in HK is cancer)
Use age-standardised rate for incidence:
- more accurate way to measure success of intervention
- ∵ age composition of society change with time
—> aging population will have more cancer incidence
Nasopharyngeal cancer:
- ↓ trend in HK
Male:
- No. of cancers ↓
Female:
- No. of cancers ↑
HK Cancer Strategy 2019
- To reduce incidence + mortality of cancer
- To adopt a holistic approach for cancer care
- To improve ***QoL of patients through better access to evidence-based prevention, screening, early detection + diagnosis, effective treatment + palliative care
- To transform concept of care for survivors + perceive cancer as a chronic illness
- To capitalise on innovation, technology, surveillance system, scientific research
Principles in War against cancer
- Prevent the preventable
- Treat the treatable
- Palliate the incurable
Cancer prevention
- > 1/3 cancers preventable
Risk factors:
- UV light
- >90% of skin cancers preventable by sun protection
- avoid using artificial UV for tanning - Smoking
- associated with 17 different cancers
- MPOWER: Monitor, Protect, Offer, Warn, Enforce, Raise (tax level recommended: 70% of retail price) - Infections
- H. pylori: Gastric cancer
- HPV: Cervix, Oropharyngeal cancer
- HBV, HCV: Liver
- EBV: Nasopharyngeal cancer
—> ***Vaccinations - Unhealthy diets / Obesity / Physical inactivity
- ↑ Risk of 13 types of cancer
- Red meat, processed meat, salted fish, aflatoxins - Alcohol
- 4.2% of cancer deaths attributed to alcohol
- problem: no threshold established - Reproductive / Hormonal factors
- Breast cancer
—> ↑ risk: HRT, OC pills
—> ↓ risk: Childbearing, Breastfeeding - Occupational carcinogens + Environmental pollutants
Recommendations from CHP to reduce cancer risk
- Quit smoking
- Reduce alcohol intake
- ↑ Fruit + vegetable, ↓ Red / processed meat
- Vaccination
- Avoid over exposure to UV
- Breastfeed
- Appropriate regular exercise
- Maintain healthy body weight
General recommendations on healthy lifestyle to prevent cancer:
- No smoking
- Maintain weight: BMI 18.5-22.9
- Maintain regular physical activity
- 150 mins moderate activity / 75 mins vigorous activity per week - Limit alcohol
- <=2 drinks (men) / 1 drink (women) - Healthy diet
- >=3 portions of fresh vegetables + 2 portions of fruits
- <=500g red meat per day + avoid processed meat - Avoid over exposure to UV
Early detection of cancer
- Screening of asymptomatic people
Principles of cancer screening:
- Well-recognised natural history of the condition: development from latent to confirmed malignancy
- Effective treatment for detected cancer
- Suitable test / examination with high level of accuracy
Population screening:
- Cancer should be an important health problem
- Cost-effective analysis consideration: Cost of screening (including Dx + Tx) should be economically balanced in relation to possible Expenditure on medical care as a whole
- Alertness to presenting features
- enhance public education of symptoms of common cancer
Advantages + Disadvantages of cancer screening
Advantages:
- Better outcome
- Less radical treatment needed
- Reassurance for those with true negative results
- Psychological benefit to population
- Savings may occur because treatment for early stage screen-detected cancer may be less complicated
Disadvantages:
- Longer morbidity if prognosis is not altered
- Over treatment of borderline abnormalities
- False reassurance for those with false -ve results
- Unnecessary investigations of false +ve results
- Resource costs of screening system
- SE / complications of invasive investigations
Colorectal cancer
Prevention measures:
- Healthy diet
- ↑ fruit + vegetable (daily intake of 25g fibre / 5 portions of fruit + vegetable)
- ↓ red + processed meat - ↑ Physical activities
- Maintain health body weight
- Avoid / quit smoking
- Limit alcohol consumption
Screening:
- ***Whole population aged 50-75 yo (Strongly recommended)
- launched in 2016
- 3 year pilot programme
- FOBT: subsidy $280 / case
- Colonoscopy: subsidy $7800-8500 / case
- Faecal occult blood
- ↓ incidence 5%
- ↓ mortality 14%
- relatively cheap, easy to do, non-invasive
- positive tests —> complete colonic evaluation (ideally colonoscopy)
- Faecal immunochemical test (FIT) preferred to chemical test ∵ **fewer false +ve + more **specific to colon
- Sensitivity limited ∵ many CRC only bleed ***intermittently - Sigmoidoscopy
- ↓ incidence 18%
- ↓ mortality 28%
- Flexible sigmoidoscopy (FS) every 5 years
—> simple, no sedation needed
—> once-only flexible sigmoidoscopy screening for 55-64 —> substantial + long-lasting benefit for CRC: ↓ incidence 33% + ↓ mortality 43%
- limitations: Rectum + Sigmoid only account for ***~60% of CRC - Colonoscopy
- every 10 years (take long time to develop from polyp to cancer)
- significant impact shown by case-control + cohort studies
- sensitivity >90% + specificity >99%
- ***polypectomy: >50% ↓ in CRC incidence
- limitations:
—> no RCT yet to demonstrate ↓ mortality
—> sedation needed
Cervical cancer
Carcinogenesis / Natural history:
- ***Orderly sequence
- ***Long latency
- Lifetime risk of acquiring at least 1 HPV infection estimated >90%
- Majority of these infections are transient
- > 100 HPV types, 13 associated with cervical intraepithelial neoplasia
- Most HPV infection never progress beyond low grade disease (CIN 1)
- 80-90% of low grade cervical abnormalities regress spontaneously
- Orderly Progression:
HPV infection —> high grade lesion —> invasive cancer
Prevention measures:
- Preventive vaccine before becoming sexually active
- Practice safe sex
- Avoid or quit smoking
- Healthy diet: rich in fresh fruit & vegetables
Screening: Strongly Recommended: - Female population aged 25-64 years —> as soon as start sexual activity —> Vaccination does NOT substitute for Screening (∵ vaccine cannot prevent all cervical cancer (cannot cover all HPV strains))
Local cost-effectiveness analysis:
- organised screening with conventional cytology every 3 years produced >90% ↓ in lifetime risk of cervical cancer compared to no screening
- **Current Recommendation in HK:
- ***Cervical smear (liquid-based Pap) at 3-yearly intervals after 2 consecutive normal annual smears (1, 1, 3-yearly cycle)
Presentation pattern by stage in HK:
- 32% stage I & 30% stage II at diagnosis (2015)
- screening programme now still not well-used esp. by high risk groups (e.g. sex workers)
Other screening test: HPV DNA test
Advantages:
- Self testing
- patient collect vaginal sample herself & then send sample to lab - High sensitivity for detecting HSIL
- compared with Pap smear test, HPV DNA test is **more sensitive for HSIL but **less specific
- sensitivity as high as 90% with a specificity of 50-70% - HPV can precede cytology changes
- persistent HPV infection may progress to LSIL then —> HSIL - Potential spacing of screening
- from 3 to 5 years
- Evidence suggest that HPV DNA testing in conjunction with Pap smear cytology may improve screening efficacy & further reduce mortality
- Main challenge is to find a good triage method to select patients for ***colposcopy
WHO pledge to eliminate cervical cancer globally by 2030
WHO target 90:70:90
- 90% coverage of HPV vaccination of girls <15
- 70% coverage of screening (70% women screened with high-performance tests by 35, 45) + 90% treatment of precancerous lesions
- Management of 90% of invasive cancer cases
Target:
- 30% ↓ in mortality from cervical cancer
Breast cancer
Prevention measures:
- Maintain healthy body weight
- ↑ Physical activities
- Limit alcohol consumption
- Healthy diet
- ↑ Consumption of fruit & vegetable (daily intake of 25g fibre / 5 portions of fruit & vegetable) - Cautious about post-menopausal replacement using combined estrogen-progestogen hormone
- Consider earlier childbirth
- Consider breastfeeding for longer duration
Screening:
- Breast self-examination (BSE)
- low sensitivity
- **no reduction in mortality / improvement in stage distribution
- **insufficient evidence —> still should encouraged —> familiar with their breast to report any obvious / persistent changes promptly - Clinical breast examination (CBE)
- sensitivity 54% + specificity 94%
- lack of RCT, ***insufficient evidence
- Cochrane review: screening by BSE / CBE could not be recommended at present - Mammography (MMG)
- sensitivity 83-95%, false positive 0.9-6.9
- 20% ↓ mortality by routine screening
- screenee ≥50 yr: higher sensitivity & greater mortality ↓
- 15% relative (0.05% absolute) risk reduction
- Over-diagnosis & over-treatment 30% (0.05% absolute risk increase)
- more difficult in Chinese population
—> ∵ **lower incidence than USA
—> ∵ **dense breast (difficult mammogram interpretation)
- ***no significant ↓ in breast cancer mortality in adequately randomised trials
—> still many countries recommend ∵ big health problem
Mammography in HK
- Insufficient evidence to recommend for or against population-based mammography screening for general female in Hong Kong
Recommendation by HK Anti-cancer Society:
- Consider screening at least for high-risk cohorts (BRCA gene mutation / family of breast + ovary cancer)
- If screen, consider starting at age ***40 (18% of invasive cancer and 19% of carcinoma-in-situ patients aged ≤45 yr)
- Further ***cost-effective analyses for general population
Liver cancer
Prevention measures:
- Preventive vaccine against HBV at birth
- Safety measures against transmission of HCV through blood transfusions
- Limit alcohol consumption
- Avoid fermented peanut (aflatoxin)
- Avoid or quit smoking
Screening:
- High-risk cohort - chronic hepatitis carrier & known liver cirrhosis
1. Half-yearly USG + AFP - ↓ HCC mortality by 37%
HK recommendation:
- Routine screening by AFP or USG for asymptomatic persons at **average risk is **NOT recommended
High risk patients:
- HBV carrier
- Known cirrhosis
Lung cancer
Prevention measures:
- Avoid or quit smoking
- Healthy diet
- ↑ Consumption of fruit & vegetable (daily intake of 25g fibre / 5 portions of fruit & vegetable)
Screening:
- Consider **low dose CT for **heavy smokers (CXR not sensitive enough)
(USPSTF 2013 recommends annual screening with low-dose CT in adults 55 to 80 yo who have a 30 pack-year smoking history, currently smoke or quitted within the past 15 years)
—> serious concern about cost-effective
—> no conclusion
