Discussion
Axillary lymph node status is one of the most important prognostic factors in early breast cancer and is guiding for personalized medicine. Historically, ALND has been used as the most accurate and reliable method to evaluate axillary but ALND has complications such as lymphedema, shoulder dysfunction, nerve injuries that restrict functions and impair quality of life. SLNB is a less invasive method to evaluate lymph node status [5]. The concept of SLNB is based on the idea that tumors are regularly drained through the lymphatic system [6]. Therefore sentinel lymph node (SLN) is the first lymph node where metastasis occurs. SLNB has replaced ALND in the evaluation of axilla in early-stage breast cancer [7].
Over the years, methods such as dyers and radioactive substance injection have been used alone or in combination to detect SLN. Studies have shown that the combined use of preoperative scintigraphic mapping, intraoperative blue dye and gamma probe methods increase the success of SLN detection in breast cancer[8]. However, it is not possible to detect SLN in 1-2% patients in breast cancer with conventional methods [9]. Techniques applied by each center may differ but overall SLN detection and accuracy rates are over 95%. In our clinical practice we use the combination of radioactive substance and methylene blue injection.
In this study, we examined the effects of taking delayed images on our surgical practice. Guidelines for the timing of lymphoscintigraphy are not clear [1, 10]. Early or delayed image acquisition time is left open-ended in the guidelines and no definite time is specified [1, 11]. NCCN (National Comprehensive Cancer Network) guidelines for breast cancer do not provide detailed information about when to acquire lymphoscintigraphy images and when a delayed image is necessary [2]. In 2014, the German Society of Nuclear Medicine published a guideline on this issue and these instructions refer to the necessity to acquire delayed images within 24 hours following an early image[11].
In a study where Taumberger et al. evaluated early and delayed images, increased uptakes were obtained in delayed images from 52% of the patients who provided no increased uptakes in early images [12]. In our study, before the pandemic increased uptake were obtained in delayed images in 22 of 23 patients (95.6%) who did not provide increased uptakes in early images. Likewise during the pandemic period, in 12 (16.4%) of the patients whose delayed images were not acquired, increased uptakes could not be obtained.
Single-Photon Emission Computerized Tomography (SPECT) images taken after the radioactive substance is given in lymphoscintigraphy shows axillary drainage pathways and the number of increased uptake lymph nodes [1, 13]. With the help of the gamma probe, the surgeon will have information about the region where he will search for SLN and the number of SLNs to remove.
The increased uptake duration in lymphoscintigraphy varies according to the location, characteristics and size of the tumor, the patient’s neoadjuvant treatment, Body Mass Index (BMI), and the distance between the breast tissue and the axilla [4, 14]. increased uptake is observed in early SPECT images in a group of patients, and not observed in others. Delayed images are preferably taken in patients without fluorescence in early SPECT images. In our center, the delayed image acquisition time is 2 hours after the early image. In this way the aim is to detect in delayed imaging the lymph nodes that cannot be displayed in the early imaging.[15]. During the COVID-19 pandemic, we made SLNB applications by taking only an early SPECT image to reduce the risk of transmission by shortening the waiting time in our center. Therefore, our study is designed to determine how the results of SLNB are affected in patients without delayed lymphoscintigraphy.
To list the main results we obtained in this study; first we found that there were fewer SLNs in patients who underwent SLNB without delayed lymphoscintigraphy (mean 2.68 / 3.19). This difference was not statistically significant (p = 0.146) but the results obtained were due to the limited number of patients and a statistically significant difference could occur if the number of patients was higher. The main reason for this is that we do not know how much SLN increased uptake was to be seen in some of the patients who did not have delayed images. Therefore, as clinicians, we cannot predict a lower limit for the number of LNs we need to remove. For example, we may try to remove 3 SLNs in a patient with 3 increased uptake. If we do not have lymphoscintigraphy and found only 1 SLN, then we end the process. This situation shows us that if there is no delayed image we remove less SLNs and terminate the process. However the most important result is that our rate of SLN detection is lower in patients without delayed imagery. Although there was a ratio of 7 to 2 in our study, no statistically significant difference was found (p = 0.097). However if this study was conducted with a larger number of patients, we could have found a significant difference. The main parameters that will reveal the reliability and effectiveness of SLNB are the rate of detection, sensitivity, specificity, NPV, PPV and accuracy rates. We have observed that the absence of delayed images reduces the rate of SLN detection. ALND is applied to all patients whose SLN is not detected. As a matter of fact, we had to perform ALND in 7 patients (9.5%) in the group without delayed imaging, as their SLN was not detected. In 5 of them, there was no axillary metastasis. In the end, this situation led to unnecessary axillary dissection in 5 of 73 patients. In addition, we have seen that our NPV value is lower in our SLN attempts without delayed images in PP. We also observed that our FNR rate is higher in PP with a rate of 4 to 2. This, in turn reduced the accuracy rate of our SLN procedures made in this period. Although the general results of our procedures performed without acquiring delayed image in PP are within the acceptable limits in the literature, we get better results in the same period when delayed images are acquired. Although acceptable accuracy and detection rates were attained, we have concluded that the figures are better in the procedures performed by taking delayed images. Our suggestion is to perform SLNB by taking the delayed images.
In conclusion we believe that if technically possible, delayed images taken during the lymphoscintigraphy can assist the surgeon in terms of SLN detection and the number of SLNs removed.