Understanding Diagnostic Tests on Cancer

Dr Vince Vardhanabhuti Clinical Assistant Professor

Objectives

• Diagnostic Tests • Imaging Modality • Utility of Imaging in Cancer

– Benefits – Harms/Risks of Imaging

• Scenarios

• Q&A

1hr

30min

Diagnostic Tests

Lab Tests

Imaging

Blood tests Tumour markers

-AFP (liver) -CEA (colon)

-CA-19-9 (pancreas) -CA-125 (ovarian)

-PSA (prostate)

Stool Tests FOB (faecal occult blood)

Biopsy

X-rays US CT

MRI PET/CT

Nuclear Medicine Scans PET/MRI

Direct visualisation

Endoscopy Colonoscopy

Alpha-fetoprotein (AFP) Cancer types: Liver cancer and germ cell tumors How used: To help diagnose liver cancer and follow response to treatment; to assess stage, prognosis, and response to treatment

of germ cell tumors Beta-2-microglobulin (B2M) Cancer types: Multiple myeloma, chronic lymphocytic leukemia, and some lymphomas How used: To determine prognosis and follow response to treatment Beta-human chorionic gonadotropin (Beta-hCG) Cancer types: Choriocarcinoma and testicular cancer How used: To assess stage, prognosis, and response to treatment BCR-ABL fusion gene Cancer type: Breast cancer How used: To assess whether treatment is working or disease has recurred CA19-9 Cancer types: Pancreatic cancer, gallbladder cancer, bile duct cancer, and gastric cancer How used: To assess whether treatment is working CA-125 Cancer type: Ovarian cancer How used: To help in diagnosis, assessment of response to treatment, and evaluation of recurrence Carcinoembryonic antigen (CEA) Cancer types: Colorectal cancer and breast cancer How used: To check whether colorectal cancer has spread; to look for breast cancer recurrence and assess response to treatment

Tumour Markers

None are sensitive or specific enough to use solely as tool to screen

for cancer.

Most can give you an indication that there may be underlying

malignancy.

Most useful in assessing treatment response and

recurrence.

Lab Tests

• Endoscopy • Colonoscopy

Direct visualisation

Endoscopy An endoscopy

procedure involves inserting a long, flexible tube (endoscope) down your throat and into your esophagus. A tiny camera on the end of the endoscope lets your doctor examine your esophagus, stomach and the beginning of your small intestine (duodenum).

Direct visualisation

Endoscopy An endoscopy

procedure involves inserting a long, flexible tube (endoscope) down your throat and into your esophagus. A tiny camera on the end of the endoscope lets your doctor examine your esophagus, stomach and the beginning of your small intestine (duodenum).

Direct visualisation

Colonoscopy is the endoscopic

examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions

Direct visualisation

Colonoscopy is the endoscopic

examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions.

Direct visualisation

Modality

• X-rays • US • CT • MRI • PET/CT

Imaging

Imaging Modality

• X-rays • US • CT • MRI • PET/CT

Imaging Modality

• X-rays • US • CT • MRI • PET/CT

Imaging Modality

• X-rays

• US • CT • MRI • PET/CT

Imaging Modality

• X-rays

• US • CT • MRI • PET/CT

Imaging Modality

• X-rays

• US • CT • MRI • PET/CT

Imaging Modality

• X-rays • US

• CT • MRI • PET/CT

Imaging Modality

• X-rays • US

• CT • MRI • PET/CT

Imaging Modality

• X-rays • US • CT

• MRI • PET/CT

Imaging Modality

• X-rays • US • CT

• MRI • PET/CT

Imaging Modality

• X-rays • US • CT • MRI

• PET/CT

Utility of Imaging in Cancer

Screening

Diagnosis

Asymptomatic Investigation of symptoms

Treatment Response

Known disease to assess response

to treatment

Screening

Concept: • Cancer that is found early often is small and can sometimes

be cured or treated easily. • Treating certain cancers early can help people live longer. • Sometimes, screening finds cells that do not yet show cancer,

but that might turn into cancer cells – so called “pre-cancerous lesions”. – This can be treated before it has a chance to become cancer

Screening

Screening Which cancers can people be screened for? • Cervical cancer – “Pap smear.”

– Age: 21 - 65

• Breast cancer – “mammogram.” – Age: 50-75. – Women who have a strong family history of breast cancer might begin

screening earlier.

• Colon cancer – “Stool FOB” “Optical Colonoscopy” “CT Colonography” – Age: 50+ – Usually for FOB +ve

• Lung cancer – “low dose CT scan.” – Age 50+ and current/ex-smoker

Screening

Imaging Tests

• The choice of imaging tests depend on the clinical suspicion.

• The best test is the one that can give you the most accurate info, fastest, and at most cost-effective manner.

Diagnosis

Benefits

• Revolutionized the diagnosis of many diseases and conditions, have improved treatment planning, and save lives (e.g. via image-guided therapies).

• Vastly reduced the need for exploratory surgery and greatly improves the efficiency of many kinds of surgical procedures.

• Even though the scans are expensive, they can reduce costs by making hospital stays shorter – so more cost-effective.

Risks/Harms - Radiation

US X-Rays

MRI

CT

PET-CT

Nuclear

No Radiation

Has Radiation

Fluro

• This effect is typically thought to be stochastic, – i.e. it can occur at any level of radiation exposure

with the likelihood increasing as the dose increases.

• The typical lag period between radiation exposure and cancer diagnosis is at least 5 years, and in most cases, the lag period may be 1 or 2 decades or longer.

Amis ES, Butler PF, Applegate KE, et al. American College of Radiology white paper on radiation dose in medicine. J Am Coll Radiol. 2007;4:272-284.

Evidence

• Radiation-induced risk is more controversial at doses between 10 and 100 mSv, but probably a small but real risk still present.

• A widely used figure is a 5% excess risk of death from cancer with a 1 Sv (1000 mSv) dose (1-2).

• Relative to the natural incidence of cancer mortality of approximately 25%

1. International Commission on Radiological Protection. 1990 Recommendations of the International Commission on Radiological Protection. Ann ICRP. 1991;21(1-3):1-201. 2. National Council on Radiation Protection and Measurements. Limitation of Exposure to Ionizing Radiation. Bethesda, MD: National Council on Radiation Protection and Measurements: 1993.

• Radiation is harmful… but at doses typically used for diagnosis is ‘probably’ acceptable weighing in long potential term risk and likely benefit.

• Special groups must justify exposure – Pregnant (dose to fetus) – Young patients (i.e. less than 40 years) organs are

more radiosensitive • Especially for children

Problems • Scans not properly administered

– Without taking the right precautions, a patient may be exposed to too much radiation, thereby increasing the risk without increasing the benefit (e.g. New York CT brain perfusion)

• Lack of standardization – For example, 2009 study found that in the San Francisco Bay

area alone, the dose of radiation given in the same kind of CT scan varied 13-fold between the highest and lowest dose given by different hospitals.

• Lack of justification – More and more, doctors may prescribe scans that aren't

medically justified. And since risk from radiation exposure accumulates over a lifetime, certain scans may not be appropriate for people who've already had a lot of scans.

Future Proposals

Improvement of Hardware • Requirement for makers of CT and fluoroscope

devices to incorporate safeguards into the design of their machines – Requiring the devices to display, record, and

report settings and radiation dose – Requiring the devices to alert users when the

radiation dose exceeds the optimal dose for most patients

Future Proposals Improve Professional Practice • Requiring devices to transmit radiation dose information both

to the patient's medical record and to a national dose registry. • Establishing nationally recognized standard radiation levels for

each imaging procedure -- including a separate standard for children.

• Improve doctor’s education about radiation burden/risks. Empowering patients • Giving patients a "medical imaging record card" to track their

radiation exposure from scans. • Providing online tool that will allow patients to track their

own medical imaging history and to share it with their doctors.

Shortcomings of Diagnostic tests

• No diagnostic tests in 100% accurate

• There will be false positive and false negative.

Summary

• Several diagnostic tests available – Blood tests – Imaging tests – Other procedures e.g. endoscopy or colonoscopy

• Not all tests are 100% safe

– Must weight risks vs benefits • No test is 100% accurate

– But a holistic and multi-disciplinary team approach help to optimise management strategies