Optimised lymphoscintigraphy in pregnant patients with breast cancer is safe

Abstract

We agree with Dr Tek and colleagues in that research involving radiation exposure of pregnant patients should be discouraged. However, their statement that ‘it is hard to translate the results of a study conducted in non-pregnant women into pregnant women’ is questionable. As no specific information exists regarding the changes in the kinetic behaviour of radiopharmaceuticals during pregnancy, the assumption that no changes occurred was postulated. However, this assumption is fully justified in our paper [1.Gentilini O. Cremonesi M. Trifirò G et al. Safety of sentinel node biopsy in pregnant patients with breast cancer.Ann Oncol. 2004; 15: 1348-1351Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar] and strengthened by a wide list of references. Our conclusions are further supported by the following considerations. (i) Due to our optimised technique and the type of radiopharmaceutical used, there is no evidence to suggest that the biokinetics of HSA should be influenced by hormonal biological changes during pregnancy. (ii) Recently, in our institute, five patients underwent sentinel node biopsy at different stages of gestation (between 2 and 7 months). The biodistribution documented by the images did not evidence any relevant difference from non-pregnant patients and the newborns are beautiful and healthy babies. (iii) Other authors evaluated the radiation risks for the foetus from nuclear medicine diagnostic procedures [2.Morita E.T. Chang J. Leong S.P. Principles and controversies in lymphoscintigraphy with emphasis on breast cancer.Surg Clin North Am. 2000; 80: 1721-1739Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar, 3.Nicklas A. Baker M. Imaging strategies in pregnant cancer patients.Semin Oncol. 2000; 27: 623-632PubMed Google Scholar, 4.Russell J.R. Stabin M.G. Sparks RB. Placental transfer of radiopharmaceuticals and dosimetry in pregnancy.Health Physics. 1997; 73: 747-755Crossref PubMed Scopus (45) Google Scholar] and Steenvoorde et al. [5.Steenvoorde P. Pauwels E. Harding L.K. Bourguignon M. Marière B, Broerse J. Diagnostic nuclear medicine and risk for the fetus.Eur J Nucl Med. 1998; 25: 193-199Crossref PubMed Scopus (38) Google Scholar] stated that ‘the best approximation of the foetal dose is still the calculation of the dose delivered to the uterus’. (iv) In the worst hypothesis, in which all the injected radioactivity entered the blood pool and reached the urinary bladder, the absorbed doses are conservatively estimated to be 0.11 mGy to the uterus of the non-pregnant woman, 0.08 mGy to the foetus of the 3-month pregnant woman and 0.03 mGy to the foetus for the 6- and 9-month pregnant woman. It is noteworthy that the resultant doses are progressively lowered as the pregnancy stage increases, being highest for the uterus of the non-pregnant patient. (v) Publications 60 and 84 of the ICRP [6.International Commission on Radiological Protection Pregnancy and Medical Radiation. ICRP Publication 84. Annals of the ICRP. Pergamon Press, New York2000Google Scholar, 7.International Commission on Radiological Protection Recommendations of the International Commission on Radiological Protection. ICRP Publication 60.Annals of the ICRP Volume. 1991; 1–3: 21Google Scholar] state that ‘…the pregnant patient has the right to know the magnitude and type of potential radiation effects that might result from in-utero exposure. Communication should be related to the level of risk. However, communication that risk is negligible is adequate for very low dose procedures (<1 mGy to the foetus).’ Overall circumstances, including the most conservative, indicate that the absorbed doses to the foetus are much lower than 1 mGy, well below the negligible risk threshold. Finally, it is important to remember that the analysis of risks and benefits is one of the three essentials principles of radiation protection to be applied to any medical procedure involving radionuclides. In our described lymphoscintographic technique, the proposed benefits to the mother substantially exceed the possible detriment to the child. Anxiety and uncertainty to the patient must be avoided.