Radiation protection of pregnant women in radiotherapy

» Can a pregnant woman receive radiotherapy?

Yes, but important factors must be considered. The most important considerations, as suggested by the International Commission on Radiological Protection (ICRP), are:

  • The stage and aggressiveness of the tumour;
  • The location of the tumour;
  • Potential hormonal effects of pregnancy on the tumour;
  • Various therapies and their length, efficacy, and complications;
  • Impact of delaying therapy;
  • Expected effects of maternal ill-health on the foetus;
  • The stage of pregnancy;
  • Foetal assessment and monitoring;
  • How and when the baby could be safely delivered;
  • Whether the pregnancy should be terminated;
  • Legal, ethical, and moral issues.

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» A pregnant patient has cancer and needs radiotherapy. How can the foetal dose be reduced?

The foetal dose be reduced by following documented expert recommendations on foetal dose reduction.

The first consideration is if the treatment can be postponed until the foetus is at a later gestation age. If the decision is made that radiotherapy is necessary, it is important to calculate the dose to the foetus before the treatment is given. When external radiotherapy is used for treatment of tumours at some distance from the foetus, a very important factor in foetal dose is the distance from the edge of the radiation field. The American Association of Physicists in Medicine (AAPM) recommends that the following points be considered:

  • Complete all planning as though the patient were not pregnant. If the foetus is near the treatment beam, do not take portal localization films with open collimation and blocks removed;
  • Consider modifications to the treatment plan that would reduce the radiation dose to the foetus (e.g. changing field size, radiation energy). If possible use photon energies of less than 25 MV;
  • Estimate dose to the foetus using phantom measurements, a shield may be constructed with 4-5 half-value layers of lead;
  • Document the treatment plan and discuss it with the staff involved in patient set-up. Document the shielding (perhaps with a photograph); 
  • Check the weight- and load-bearing specifications of the treatment couch or other aspects of shielding support;
  • Be present during initial treatment to assure that shielding is correct;
  • Monitor the foetal size and growth throughout the course of treatment and re-assess foetal dose if necessary;
  • On completion of treatment, document the total dose including the range of dose to the foetus during therapy; 
  • Consider referring the patient to another institution if equipment and personnel are not available for reducing and estimating the foetal dose. 

Read more:

  • STOVALL, M., BLACKWELL, C.R., CUNDIFF, J., NOVACK, D.H., PALTA, J.R., WAGNER, L.K., WEBSTER, E.W., SHALEK, R.J., Fetal dose from radiotherapy with photon beams: Report of AAPM Radiation Therapy Committee Task Group No. 36, Med. Phys. 22 1 (1995) 63-82.

» A patient has been diagnosed with cervical carcinoma and has to start radiotherapy treatment. Unfortunately, she is pregnant in the first trimester. What will happen with her pregnancy?

Unfortunately, it is likely that pregnancy will be terminated.

Carcinoma of the cervix is the most common malignancy associated with pregnancy. Cervical cancer complicates about one out of 1250 to 2200 pregnancies. This rate, however, varies significantly by country. Cervical cancer is often treated by surgery/radiotherapy (external beam radiotherapy and brachytherapy) and the absorbed doses required with both forms of radiotherapy will cause termination of pregnancy. If the tumour is infiltrative and is diagnosed late in pregnancy, an alternative is to delay treatment until the baby can be safely delivered. Regardless of protective measures, radiotherapy involving the pelvis of a pregnant female almost always results in severe consequences for the foetus, most likely foetal death.

» How long should a woman wait after receiving radiotherapy for breast cancer treatment before she can consider becoming pregnant?

The wait can be substantial and needs to be discussed with her radiation oncologist.

Most radiation oncologists advise their patients not to become pregnant for 1-2 years after completion of therapy. This is not primarily related to concerns about potential radiation effects, but rather to considerations about the risk of relapse of the tumour that would require more radiation, surgery or chemotherapy.

» A patient just finished four weeks of radiation treatment to the neck area for non-Hodgkin's lymphoma. After one month, she got pregnant. What are the possible effects on the foetus?

There is no likely effect.

Radiation exposure occurred before conception, so any effect on the offspring would be classed as genetic effect. No data from humans show any statistically significant genetic effect in any population, even the Japanese atomic bomb survivors. All estimates of genetic radiation risk come from studies of rodents, which show that males are far more sensitive than females. However, it is not easy to extrapolate this data to humans.

There is very low risk of any effect on the unborn child. The World Health Organization estimates that the worldwide incidence of inherited disease (ranging from severe to as trivial as an inconspicuous birthmark) is about 10%. In the unfortunate event that the child is born with any genetic abnormality, it is extremely unlikely that it would be related to the earlier radiation exposure.

» What is the risk to a foetus if a man who has had a radiation pellet inserted into his prostate for cancer treatment comes into close proximity with a pregnant woman?

There is no danger involved.

Prostate brachytherapy can be performed with permanent implantation of radioactive 103Pd or 125I seeds, and the patient is discharged from hospital with these in place. The short range of the emissions from these radionuclides is the reason that the patient can be discharged and is the reason that these patients pose no danger to pregnant family members. Other brachytherapy patients are kept in the hospital until the sources are removed. While these patients can occasionally be a source of radiation to a pregnant family member, the potential dose to the foetus is very low, irrespective of the type of brachytherapy.

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