Hueman Matthew T, Scanlan Bradford J, White Paul W, Golarz Scott R, Peoples George E, Shriver Craig D, Maniscalco-Theberge Mary E
Department of Surgery, Walter Reed Army Medical Center, Washington, District of Columbia, USA.
Curr Surg. 2002 May-Jun;59(3):313-7. doi: 10.1016/s0149-7944(02)00624-4.
Sentinel lymph node (SLN) biopsy has been increasingly accepted in many centers as an alternative to axillary lymph node dissection in the nodal staging of breast cancer. The goal of SLN biopsy is to accurately stage the axilla while minimizing postoperative morbidity. Theoretically, the continuing search for SLNs disrupts additional lymphatics and impacts on operative time. The gamma count threshold is a predefined threshold percentage of the ex vivo count of the "hottest" SLN, which when applied to each individually excised lymph node determines whether a given lymph node is the SLN or a non-SLN. The higher the threshold percentage, the less the number of lymph nodes will meet the criteria of being an SLN. This study examines the hypothesis that changing the gamma count threshold from 10% to 50% will not significantly affect accuracy or the false-negative rate.
We retrospectively reviewed the charts of patients who underwent SLN biopsy with or without completion axillary lymph node dissection from March 1995 to January 2001 at Walter Reed Army Medical Center. Data were collected on gamma counts for each SLN and histopathology of each SLN. For each SLN ex vivo gamma count, percentage of the ex vivo gamma count of the "hottest" SLN was calculated.
The SLN identification success rate was 94% (163 out of 174 patients). On average, 2.07 SLNs were removed per patient and 58% of patients had more than 1 SLN removed (94 out of 163 patients). Only 10% had 4 or more SLNs removed (17 out of 163 patients). Sentinel lymph node metastasis was found in 21% of patients (35 of 163 patients). Of these 35 patients with positive SLNs, 8 patients had a negative "hottest" SLN when a less radioactive SLN was positive for metastasis. Changing the gamma count threshold from 10% to 50% lowers the extrapolated accuracy from 98% to 95% and increases the extrapolated false-negative rate from 8% to 21%.
The accuracy and false-negative rate of SLN biopsy varies based on the lower limit gamma threshold. Maintaining our 10% gamma count threshold results in acceptable accuracy and false-negative rates comparable to reported literature.
前哨淋巴结活检在许多中心已越来越多地被接受，作为乳腺癌腋窝淋巴结分期中腋窝淋巴结清扫术的替代方法。前哨淋巴结活检的目标是在使术后发病率降至最低的同时准确对腋窝进行分期。理论上，持续寻找前哨淋巴结会破坏更多淋巴管并影响手术时间。γ计数阈值是“最热点”前哨淋巴结体外计数的预先定义的阈值百分比，将其应用于每个单独切除的淋巴结可确定该淋巴结是前哨淋巴结还是非前哨淋巴结。阈值百分比越高，符合前哨淋巴结标准的淋巴结数量就越少。本研究检验了将γ计数阈值从10% 更改为50% 不会显著影响准确性或假阴性率这一假设。
我们回顾性分析了1995年3月至2001年1月在沃尔特·里德陆军医疗中心接受前哨淋巴结活检（无论是否完成腋窝淋巴结清扫）的患者病历。收集了每个前哨淋巴结的γ计数以及每个前哨淋巴结的组织病理学数据。对于每个前哨淋巴结的体外γ计数，计算其占“最热点”前哨淋巴结体外γ计数的百分比。
前哨淋巴结识别成功率为94%（174例患者中的163例）。平均每位患者切除2.07个前哨淋巴结，58% 的患者切除了1个以上的前哨淋巴结（163例患者中的94例）。只有10% 的患者切除了4个或更多前哨淋巴结（163例患者中的17例）。21% 的患者（163例患者中的35例）发现前哨淋巴结转移。在这35例前哨淋巴结阳性的患者中，当放射性较低的前哨淋巴结转移呈阳性时，有8例患者的“最热点”前哨淋巴结为阴性。将γ计数阈值从10% 更改为50% 会使外推准确率从98% 降至95%，并使外推假阴性率从8% 增至21%。
前哨淋巴结活检的准确性和假阴性率因γ阈值下限而异。维持10% 的γ计数阈值可获得与已发表文献相当的可接受的准确性和假阴性率。
