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.