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Mahesh

17/12/23 18:00 PM IST

CT scans associated with increased risk of blood cancers

In News
  • The benefits of CT imaging in clinically needed cases are well known.
  • However, its potential for increased cancer risks and relatively high cumulative doses from multiple scans have raised concerns among the medical and scientific community.
Radiation doses
  • Radiation doses at moderate (over 100 mGy) to high (over 1 Gy) values are known to cause haematological malignancies (blood cancers) in both children and adults and other cancers.
  • However, there has been uncertainty about risk at low doses (less than 100 mGy) that are typically associated with diagnostic CT examinations.
  • A recent study suggests that even low doses of radiation have a small probability to cause blood cancer.
Major findings
  • The final study covered about 1.3 million CT scans in nearly 9,00,000 patients.
  • They estimated the radiation doses to the active bone marrow of each subject based on the body part scanned, patient characteristics, time period and inferred CT technical parameters.
  • Fifty-one percent of the cases were younger than 20 years at diagnosis, whereas 88.5% were younger than 30 years.
  • The researchers found a clear association between cumulative dose and risk of all haematological malignancies, with an excess relative risk of 1.96 per 100 mGy.
  • Gray (Gy) is a unit of absorbed dose of radiation. The energy absorbed in one Gy of radiation is one Joule per kg of tissue.
  • Since Gy is a large unit, milli (one-thousandth) or micro (one-millionth) of a Gy are commonly used.
  • Researchers estimated that “for every 10,000 children examined today (mean dose 8 mGy), one-two persons are expected to develop a haematological malignancy attributable to radiation exposure in the subsequent 12 years.
  • It is a large-scale multi-centre study designed to estimate directly the risk of blood cancers associated with ionizing radiation exposure from CT examinations during childhood and young adulthood; it aims to address criticisms of previous studies related to dosimetry, statistical power and potential biases.
  • The size of the study (nearly one million patients) has considerably increased the statistical power compared with previous national studies.
  • The results showed a clear dose-response between cumulative ABM dose and risk of haematological malignancies, both lymphoid and myeloid, with increased risk at doses as low as 10-15 mGy.
Way forward
  • It is a curtain down on the dose-effect controversy; low dose ionising radiation causes a finite risk not greater than what was estimated thus far from various studies.
  • This small risk is acceptable in view of clinical benefits to the patient. Patients must realize that denying to undergo CT scans needed to diagnose disease is also harmful.
  • The study highlights the need for diligently following the basic principles of radiation protection.
Source- The Hindu

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