Radiation safety of the sentinel lymph node technique in breast cancer

Many publications attest to the potential of the sentinel lymph node techni que in advancing the clinical management of melanoma and, more recently, br east cancer. Whilst not yet universally regarded as the standard of care, t he technique is gaining wide acceptance. Use of a radiolabelled colloidal t racer is central to optimising sensitivity, and this brings with it the nee d to address radiation safety issues relating to the use of radioactive mat erials in the operating theatre and pathology laboratory, and the generatio n of radioactive waste. The radiation dose to the patient should also be de termined if the professional is to reassure the patient by placing this in its proper context. For the purpose of this investigation, biodistribution data were obtained from patient studies to quantify the migration of tracer beyond the injection site, thereby permitting a detailed assessment of the internal dosimetry of the tracer and the resulting radiation dose to the p atient. Uptake of tracer in the sentinel nodes, reticulo-endothelial system and circulating blood was investigated. The radiation dose to surgical sta ff was recorded using whole-body monitors and extremity dosimeters worn at the fingers. Clinical waste in the operating theatre was monitored and the radioactive content of significantly contaminated items determined. The rad iation dose to pathology staff was estimated from knowledge of the radioact ive content of the specimens obtained and a study of work practices. Migrat ion of tracer was found to be minimal, with greater than 95% retention at t he injection site. The effective dose resulting to the patient was 2.1 x 10 (-2) mSv/MBq, with a mean breast dose of 7.2 x 10(-1) mGy/MBq, A mean whole -body dose of 0.34 mu Sv was received by surgical staff per procedure, with a mean finger dose of 0.09 mSv (90 mu Sv). Radiation doses received by pat hology staff will be predominantly below measurable levels and are likely t o be negligible unless primary specimens from a large number of studies are analysed promptly upon their excision. At operation, surgical swabs can be come significantly contaminated and have been found to contain up to 22% of the administered activity, dependent upon the surgical procedure performed . It is concluded that moderate activities of technetium-99m labelled trace r are administered to the patient: and the radiation risk to the patient is consequently low relative to that from many other medical exposures. The r adiation doses to staff groups involved in all aspects of the technique are low, and under normal circumstances and levels of workload, routine radiat ion monitoring will not be required. Standard biohazard precautions prevent direct intake of radioactive contamination. Radioactive waste is created i n the operating theatre, and may be generated in the pathology laboratory i f specimens are not routinely stored until fully decayed. This will require special handling if the disposal of radioactive material is not permitted.