Near-infrared fluorescent lymphography after injection of indocyanine green enabled surgeons to effectively identify and thoroughly retrieve draining lymph nodes in patients with gastric cancer, according to a prospective, single-arm study published in JAMA Surgery.
“In the present study, we tested the hypothesis that peritumoral injection of indocyanine green at a sufficient time before surgery would allow for visualization of every draining lymph node from the primary tumor under near-infrared imaging, facilitating more complete lymphadenectomy of regional lymph nodes during gastrectomy,” In Gyu Kwon, MD, professor in the department of surgery at Yonsei University College of Medicine in Seoul, South Korea, and colleagues wrote.
“Moreover, we suspected that the use of near-infrared imaging when retrieving lymph nodes from the resected specimens would facilitate the harvesting of small fluorescent lymph nodes that would otherwise prove difficult to identify by conventional, manual methods of lymph node retrieval.”
The analysis included 40 patients (men, n = 21; mean age, 52.2 years; standard deviation [SD], ± 11.7; range, 20-80) slated to undergo robotic gastrectomy at Yonsei University Medical Center between Aug. 30, 2013, and July 21, 2014.
All patients had histologically confirmed gastric adenocarcinoma, tumors smaller than 4 cm in diameter, and clinical stage 1 disease (T1N0M0, T1N1M0 and T2N0M0).
Researchers propensity score-matched patients 1:1 with 40 historical controls who underwent robotic gastrectomy without indocyanine green injection between Jan. 1, 2012, and Aug. 31, 2013.
During endoscopy on the day before gastrectomy, patients received a 0.6 mL injection of a solution that contained 0.75 mg of indocyanine green as a fluorescent contrast agent along the stomach’s submucosal layer at four locations surrounding the primary tumor.
Lymph node metastases
The number of lymph nodes retrieved from each nodal station served as the primary outcome. Researchers reported no complications related to indocyanine green injection or imaging, and they confirmed the absence of fluorescent lymph nodes after lymphadenectomy.
Researchers dissected 432 lymph node stations — including 289 stations were fluorescent and 143 that were nonfluorescent — containing 1,956 lymph nodes from the near-infrared group. Researchers harvested a mean total of 48.9 (SD, ± 14.6) lymph nodes per patient, and 4.5 (SD, 3.5) lymph nodes per station.
Among the nodes, 1,590 were from fluorescent stations and 366 were from nonfluorescent stations. Patients each had a mean total of 23.9 (SD, ± 9) fluorescent lymph nodes, and 3.3 (SD, 3) fluorescent lymph nodes per station. Five patients in the near-infrared group had lymph node metastases, all of which were seen in fluorescent lymph nodes.
The researchers retrieved significantly more lymph nodes from fluorescent vs. nonfluorescent stations (mean, 5.5; SD, ± 4.1 vs. 2.5; SD, ± 2.7; P < .001). Moreover, the near-infrared group had a larger mean number of overall lymph nodes retrieved vs. the control group (48.9 vs. 35.2; P < .001).
The overall mean number of lymph nodes per station was higher in the near-infrared group compared with the control group (4.5 vs. 3.3; P < .001), but researchers only observed significant differences for stations 2, 6, 7, 8 and 9.
The researchers cited several limitations to the study, including its nonrandomized, nonblinded nature and enrollment of patients with relatively early-stage disease and low lymph node metastasis.
They also noted that because it was not possible to mask surgeons for fluorescent lymphography during surgery, the surgeon was potentially biased regarding the degree of lymph node dissection.
"The study adds to the existing body of evidence supporting the use of near-infrared fluorescent lymphography during surgery for gastric cancer," Marco G. Patti, MD, professor of surgery and co-director of the center for esophageal diseases and swallowing at the University of North Carolina at Chapel Hill, and colleagues wrote in a related editorial.