The sentinel lymph node: Relevance in gynaecological cancers

Added value of intraoperative real-time imaging in searches for difficult-to-locate sentinel nodes

Localization of sentinel lymph nodes can be challenging if they are in difficult anatomic locations or near high radiotracer activity. The purpose of this study was to assess the value of intraoperative real-time imaging using a portable gamma-camera in conjunction with a conventional gamma-counting probe when it is difficult to localize the sentinel node.

METHODS

After (99m)Tc-nanocolloid injection, patients with various malignancies underwent presurgical lymphoscintigraphy followed by surgery (usually the next day). We evaluated 20 patients who required sentinel lymph node biopsy and in whom the location or other characteristics of the sentinel node would make intraoperative retrieval difficult. During surgery, the sentinel node was localized using a portable gamma-camera together with a hand-held gamma-probe. A (153)Gd pointer or (125)I seed was used to better depict the sentinel node location in real time.

RESULTS

Using only a conventional hand-held gamma-probe, surgeons were able to definitively localize the sentinel node in 15 of 20 patients. Intraoperatively, the portable gamma-camera showed uptake by the definite sentinel node in 19 of 20 patients and helped to precisely localize the node with the hand-held gamma-probe in 4 patients. In 1 of these patients, the sentinel node was metastatic.

CONCLUSION

The combination of a standard hand-held gamma-probe and real-time imaging provided by a portable gamma-camera offers a high intraoperative detection rate in patients with difficult sentinel node localization as assessed by presurgical lymphoscintigraphy.

Radiation dose to surgical staff from positron-emitter-based localization and radiosurgery of tumors

Surgical tissue characterization based on radiotracer uptake has become much more common in recent years, particularly due to the advent of the sentinel lymph node biopsy technique. Radiolabeled pharmaceuticals are used with hand-held gamma-sensitive probes, which are capable of localizing small tumors and lymph nodes that are first identified via scintigraphy. The radiation safety of such radioguided procedures, which typically employ 99mTc, has been well established. Now, with the emergence of 18F-fluorodeoxyglucose (18FDG) as a widely used tracer for PET imaging of cancer patients, there is increasing interest in the possibility of utilizing 18FDG for intraoperative tumor detection. First, though, the exposure to operating room personnel must be shown to be at a safe level. Due to the short half-life of 18F, the exposure rate will vary significantly with the start time post-injection as well as the duration of the procedure. The aim of this investigation is to determine empirically an exposure rate equation that can be integrated to estimate the exposure to a surgeon and assistants, from patients injected with 18FDG, over an arbitrarily chosen time interval. The study was conducted by measuring the radiation exposure rate from hospital in-patients receiving 18FDG-PET scans at various times from one to seven hours post injection; the empirical equation was determined from the plot of exposure rate vs. time for all patients. The resulting effective dose equivalent for the surgeon for typical values of injected activity, delay time and procedure duration was approximately 60 microSv.

[Lymphadenectomy of the inguinal region and pelvis]

The draining lymph nodes of extra-abdominal tumors and malignant lesions of the lower extremity are located in the groin and iliac region. Malignancies with lymphatic drainage into this region include tumors of the anorectum, penis and vulva, skin (melanoma, squamous cell carcinoma), and soft tissue sarcomas. Current clinical research in biology, routes of lymphatic spread, and the possibility of marking the sentinel lymph node has directed lymphadenectomy strategy toward differential procedures, depending on the type of underlying malignancy. The spectrum of lymphadenectomy includes diagnostic lymph node removal of clinically enlarged nodes, removal of the sentinel node, and radical lymphadenectomy. Lymphadenectomy can also be indicated as a palliative procedure. The indications also depend on the type of tumor, previous treatment, and disease prognosis. This review presents the current state of indications and surgical techniques of inguinal and iliacal lymphadenectomy.