Post Injection Pain During Breast Lymphoscintigraphy: Technetium Sulfur Colloid versus Technetium Tilmanocept

Objectives: bjectives Lymphoscintigraphy is used to map lymphatic drainage and facilitate sentinel lymph node (SLN) identification and removal in breast cancer patients. It is an important procedure because it provides information about axillary node status required to properly stage breast cancer. The presence or absence of axillary node metastases carries important prognostic information and guides adjuvant therapy. For lymphoscintigraphy, a radiopharmaceutical agent is intradermally injected and SLNs are identified either preoperatively with a gamma camera or intraoperatively with a gamma probe. Traditionally, 99mTc-sulfur colloid (99mTc-SC) has been the most commonly used radiopharmaceutical for SLN mapping; however, it has been shown to cause significant post-injection site pain. A recently approved radiopharmaceutical, 99mTc-Tilmanocept (99mTc-TM), is a radiotracer that accumulates in lymphatic tissue by binding to a mannose binding receptor that resides on the surface of dendritic cells and macrophages. 99mTc-TM’s small diameter permits enhanced diffusion into lymph nodes and blood capillaries, resulting in a rapid injection site clearance. 99mTc-TM has a high SLN localization rate of >97% and a low false negative rate of <3%. It has also been reported that patients undergoing lymphoscintigraphy and SLN biopsy with 99mTc-TM report significantly less post-injection site pain. This study assessed the difference in the amount of post-injection site pain experienced by breast cancer patients after receiving an injection of 99mTc-SC or 99mTc-TM. Methods A total of 48 women, aged 18 or older, with a diagnosis of primary breast cancer who were eligible for surgery were enrolled in the study. Patients were sequentially assigned to the two treatments. Initially, all patients received 99mTc-SC (n=21). Subsequently, patients received 99mTc-TM (n=27) when it was made available. Patients received two periareolar superficial injections of approximately 250 uCi each for a total of approximately 525 uCi of either 99mTc-SC (n=21) or 99mTc-TM (n=27). Post-injection site pain was assessed immediately after the radiotracer was administered. Patients were asked to rate their level of discomfort using the Wong-Baker FACES pain rating scale immediately after injection. This pain scale is based on a numeric pain rating scale ranging from a minimum score of 0 (no pain) to 10 (worst pain imaginable) and includes six cartoon faces with written descriptions ranging from 0 (No Hurt) to 10 (Hurts Worst). Results The mean pain score was significantly lower for patients receiving 99mTc-TM (2.5 ± 2.5) compared to patients receiving 99mTc-SC (7.2 ± 2.5), P<0.01. Thirty three percent (33%) of the patients receiving 99mTc-SC reported pain scores of 10 (worst pain imaginable) while no patients receiving 99mTc-TM reported pain scores higher than 8. Thirty percent (30%) of the patients receiving 99mTc-TM reported pain scores of 0 (no pain) while no patients receiving 99mTc-SC reported pain scores lower than 1.

Conclusions: Women receiving 99mTc-TM experienced significantly less post-injection site pain compared to those receiving 99mTc-SC when undergoing injection of a radiopharmaceutical for lymphoscintigraphy prior to SLN biopsy and breast cancer surgery.