Validation Study Of The Modified Injection Technique For Internal Mammary Sentinel Lymph Node Biopsy In Breast Cancer

Objective:Internal mammary lymph node (IMLN) metastasis has a similar prognostic importance as axillary lymph node involvement in breast cancer patients. With the development of sentinel lymph node biopsy (SLNB), internal mammary sentinel lymph node biopsy (IM-SLNB) might be a minimally invasive technique for effective evaluation of the status of IMLN. However, internal mammary sentinel lymph node (IM-SLN) was identified only in a small group of patients with the tradition radiotracer injection technique, which has been the restriction for IM-SLNB to date. According to the existing standard method for axillary SLNB and the hypothesis of IM-SLN lymphatic drainage pattern, we established a modified radiotracer injection technique (periareolar intraparenchymal, high volume and ultrasonographic guidance) which could significantly improve the visualization rate of the IM-SLN. The modified technique broke through the bottle-neck of the low IM-SLN visualization rate with traditional radiotracer injection technique. The accuracy of the hypothesis of ASLN lymphatic drainage pattern proved with subsequent axillary lymph node dissection (ALND). As the extended radical mastectomy has been abandoned, we cannot validate the accuracy of the modified technique by this way. In this validation study different tracers were injected in different sites to observe whether the modified technique could reflect the real lymphatic drainage of the whole breast and the IM-SLN detected by the modified injection technique is the true sentinel lymph node in the internal mammary.Methods:From December 2011 to December 2014,455 patients with core biopsy proved invasive breast cancer scheduled to receive preoperative tracers injection, who agreed with undergo IM-SLNB as part of their breast cancer surgery, were recruited to the IM-SLNB study. Patients with previous invasive breast cancer, hypersensitivity to iodine or indocyanine green (ICG), hyperthyroidism and patients who were either pregnant or lactating were excluded from the study.This is a prospective cohort study about the modified radiotracer injection technique for the IM-SLNB in breast cancer. It has three groups, including the traditional radiotracer injection technique group, the modified radiotracer injection technique group and the modified technique validation study group. In the traditional injection group, the radiotracer (0.4～1.0ml 18.5-44.4MBq 99mTc-labeled sulfur colloid) was injected in the peritumoral intraparenchyma 3-18h before surgery. In the modified injection technique group, the radiotracer (1.0～1.2ml 9.25-18.5MBq 99mTc-labeled sulfur colloid) was injected into intraparenchyma at the 6 and 12 o’clock positions 0.5～1.0cm from the areola guided by ultrasound 3-18h before surgery. In the modified technique validation study group, the radiotracer was injected with the modified technique, and fluorescence tracer (1.0ml 0.5% ICG) was injected in the peritumoral intraparenchyma 5min before surgery. The radioactive IM-SLNs were detected by preoperative lymphoscintigraphy (Toshiba GCA 901 AHG) and/or gamma probe (Neoprobe, Neo2000 gamma detection system, Johnson & Johnson) 30min before the surgery. IM-SLNB was performed for patients with the radioactive IM-SLNs. In the validation study group, the fluorescent status of IM-SLN was identified by the fluorescence imaging system (Mingde, MD fluorescence imaging system, China). The number and the status of IM-SLNs were recorded, and statist to identify the IM-SLN visualized rate and the concordance rate of the radiotracer and the fluorescence tracer. All IM-SLNs removed from the internal mammary chain were assessed by usual pathology. Comprehensive individual documentation was kept about the radioactive counts, anatomical location, maximal diameter, IM-SLNB time and detailed histopathology of every sentinel lymph node, along with non-sentinel lymph node biopsied. The data were analyzed with the SPSS 17.0 software package. Chi-square-test or Fisher’s-exact-test was performed to compare the visualization rates among the groups, and the t-test or Mann-Whitney-test was used to compare the differences in means between the groups. Reported P values represent two-sided tests. Significance was defined as P<0.05.The study was conducted within a single institute (Breast Cancer Center, Shandong Cancer Hospital and Institute). All patients gave informed consent to participate in the study which had approval from the Shandong Cancer Hospital and Institute Research Ethics Board (No.:2005/11/15 and SDTHEC20130324). Any immediate toxicity following injection of ICG and any adverse events and reactions during the study period were recorded during surgery and at the two-week follow up appointment.Results:A total of 455 patients were enrolled.58 patients were in the traditional radiotracer injection technique group,235 patients were in the modified radiotracer injection technique group and 162 patients were in modified technique validation study group. Groups were well-balanced with regard to patient’s age, body mass index (BMI), tumor size, tumor location, tumor histological type, radiotracer intensity, radiotracer volume, and intervals from injection to IM-SLNB (all P>0.05). The overall visualization rate of IM-SLN detected by preoperative lymphoscintigraphy and/or gamma probe was significantly higher in the modified technique group than that in the traditional technique group (70.6%,166/235 vs 15.5% 9/58, P<0.001). There were no significantly difference in the visualization rate of ASLN, the detected number of ASLN and the visualized number of IM-SLN between the traditional technique group and the modified technique group (all P>0.05).There were no significant differences in the overall visualization rate of IM-SLN detected by preoperative lymphoscintigraphy and/or gamma probe in the modified technique group compared to the validation group (70.6%,166/235 vs 72.8% 118/162, P=0.858). Furthermore, the success rate of IM-SLNB, the total number of detected IM-SLN, the metastatic rate of IM-SLN, the time of IM-SLNB and the size of IM-SLN were no significant differences between the modified technique group and the validation group (all P>0.05). In patients who performed IM-SLNB under the guidance of the modified technique, a total of 409 lymph nodes were removed, the median number of IM-SLNs was 2 (range 1-4 nodes). The site of IM-SLNs concentrated in the second (46.9%,192/409) and third (39.9%,163/409) intercostal space, the metastasis IM-SLNs was located in the second (56.4%,22/39) and third (43.6%,17/39) intercostal space respectively. In the validation group,71.2%(141/198) of IM-SLN was found in the outside of the internal mammary vessels and 28.8%(41/198) was in the inside. The IM-SLN involvement rate was 6.9%(13/188) in patient with clinically axillary node negative patients and 28.2%(11/39) in positive patients respectively. IM-SLN positivity led to a more advanced nodal category in all patients and to more accurate staging in 24 of 227 (10.6%) patients. In 10 patients (4.4%,10/227), the nodal status changed from a pN0 to pN1b. In 14 patients (6.2%,14/227), the nodal status changed from a pN2a to pN3b. Changes in radiation field planning included adding postmastectomy radiotherapy that included regional nodal irradiation to the supraclavicular, infraclavicular in three patients who would have received no adjuvant radiation therapy.In the validation study group,110 patients underwent IM-SLNB successfully, of which 94 patients identified the radiotracer and the fluorescence tracer reached to the same IM-SLN, 16 patients found only the radiotracer positive IM-SLN. Accordingly, the correlation and the agreement is significant (Case-base, rs=0.808, P<0.001; Kappa=0.79, P<0.001).There were no serious adverse events or reactions during this study. A total of 9 patients had minor generalized skin reactions which occurred after injection of ICG during the surgery, but these were not necessarily attributable to the fluorescent tracer itself. A small pleural lesion was noted intraoperatively in 3.8% cases (9/236) and no pneumothorax was seen postoperatively on chest X-rays. Intraoperative bleeding from the internal mammary artery occurred in 4.7% cases (11/236), and was successfully resolved. There were no any postoperative complications and reactions after two-week follow up, and no increase days in hospital stay from this procedure.Conclusions:1. Different tracers injected into the intraparenchyma in different sites could reach to the same IM-SLN.2. It proved that the accuracy of the modified injection technique, which provide an effective technique to evaluate the status of IMLN.3. It also proved that the accuracy of the hypothesis of IM-SLN lymphatic drainage pattern, a fact that IM-SLN receives not only the lymphatic drainage from the primary tumor area but the entire breast parenchyma.4. We suggested that IM-SLNB should be performed routinely in the clinically positive ALN patients, for it could lead to a greater degree of staging accuracy and provide the accurate indication of radiation to the internal mammary area.