SANTA MONICA, CALIF. — A combination of patent blue dye and technetium-99m radiocolloid appears to be more accurate than patent blue dye alone in mapping sentinel lymph nodes in vulvar cancer, according to a study presented by Dr. Lukas Rob at the biennial meeting of the International Gynecologic Cancer Society.
Furthermore, a handheld gamma probe appeared to be more accurate and more convenient than lymphoscintigraphy in detecting “hot” nodes, said Dr. Rob of Charles University in Prague.
The nonrandomized study involved 59 women with stage T1 or T2 squamous cell cancers smaller than 4 cm in diameter. The investigators used blue dye alone in the first 16 women, and the combination of technetium-99m and blue dye in the remaining 43. Patients with suspicious or bulky lymph nodes were excluded from the study.
Of the 16 patients mapped with blue dye alone, sentinel lymph nodes were detected in 11 (69%), and there was one false negative (6%). In contrast, sentinel lymph nodes were detected in all of the patients mapped with the combination of blue dye and technetium-99m, and there were no false negatives. These differences were statistically significant.
In this second group of patients, investigators found a total of 98 sentinel lymph nodes. Of those, 82 were detected by both technetium and blue dye, 15 were detected by technetium alone, and one was detected by blue dye alone.
The investigators determined that the best time for injecting the radiocolloid was 3–4 hours before surgery. They performed the injection intradermally, peritumorally, and without local anesthesia. They used 0.2–0.4 mL of Sentiscint (15 MBq). About an hour before the operation, they conducted lymphoscintigraphy. They injected 2 mL of 2.5% Bleu Patente V 3–5 minutes before incision by the same route.
Although the handheld gamma probe showed a relatively good correlation with lymphoscintigraphy, the probe identified 14 “hot” nodes not seen in lymphoscintigraphy among the 43 women in the combination group. The investigators concluded that eliminating preoperative lymphoscintigraphy and using only the handheld probe during surgery would simplify management and result in lower costs without compromising the detection rate.
In all, the investigators detected 118 sentinel lymph nodes in 59 women. Of these sentinel nodes, 84% were in the superficial medial and intermedial inguinal chain, none were in the superficial lateral groin, and 16% were deep inguinal nodes. Dr. Rob said that one important message of the study was that it's crucial not to neglect a search for these deep inguinal nodes.