METHODS
A total of 179 patients were included in the study, and their primary tumor histopathological features,
molecular subtypes, axillary lymph node (ALN) involvement, distant metastasis, and OS were evaluated
and compared 18F-FDG PET parameters. Among the PET parameters, maximum standardized uptake
value (SUVmax), mean SUV, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the
tumor and ALNs were examined.
RESULTS
Based on molecular subtypes, the metabolic parameters of tumors were at their lowest in the Luminal A
group and had the highest values within the triple-negative BC group. The triple-negative BC subtype was
associated with a higher Ki67 proliferation index. Tumor SUVmax was higher in patients who were estrogen
receptor negative, progesterone receptor (PR) negative, had nuclear grade III, and had distant metastasis
(p=0.021, p=0.001, p<0.001, p=0.014, respectively). Patients with distant metastasis, ALN metastasis,
and internal mammary lymph node involvement had higher tumor TLG and MTV (respectively, p<0.001,
p<0.001, p<0.001). Higher ALN SUVmax values were observed in patients with distant metastasis and
those who were PR negative (p=0.016). The ALN TLG value was found to be higher in patients with distant
metastases and ALN metastases compared to those without (p<0.001, p=0.049, p=0.025, respectively).
CONCLUSION
The study indicates that PET/CT is a highly dependable method for detecting ALN involvement. Furthermore,
assessing metabolic tumor characteristics using 18F-FDG PET/CT before initiating primary IDC treatment
might provide crucial diagnostic and prognostic insights that significantly contribute to managing the disease.
Keywords: 18F-fluorodeoxyglucose positron emission; invasive ductal breast cancer; metabolic tumor volume; overall survival; tomography/computed tomography; total lesion glycolysis
Significant prognostic factors considered in BC include
the size of the tumor, multifocality, lymph node
spread, and distant metastases (DM). In addition, various
histopathological and molecular features such as
histopathological type, grade, hormone receptor status
(estrogen receptor [ER] and progesterone receptor
[PR]), human epidermal growth factor receptor
(HER2) (cerb-B2) status, and the ki-67 proliferation
index are other important factors.[
18-Fluorodeoxyglucose Positron Emission Tomography/
Computed Tomography (18F-FDG PET/
CT) has great prognostic significance in predicting
malignant tumors, TNM staging, evaluation of therapeutic
effects, the FDG parameter maximum standardized
uptake value (SUVmax), metabolic tumor volume
(MTV), and total lesion glycolysis (TLG) as a parameter
of tumor metabolism and volume are important.[
Most of the studies have collectively evaluated all
the different histological subtypes of BC, including invasive
ductal breast carcinoma (IDC), invasive lobular
breast carcinoma, mucinous carcinoma, and metaplastic
carcinoma. There are a limited number of studies
that have investigated the relationship between molecular
subtypes, immunohistochemistry features, and
overall survival (OS) determined from pretreatment
biopsy specimens of the primary tumor with volumetric
18F-FDG PET/CT parameters at the initial staging
of a homogenous group of patients diagnosed with invasive
ductal breast cancer (IDBC).[
This study aims to evaluate metabolic parameters
for the primary tumor of pretreatment 18F-FDG PET/CT in relation to molecular subtype, immunohistochemistry,
and OS only in patients with IDC.
The patient and tumor characteristics are summarized
in Table
ER and PR were considered positive when immunoreactive
cell nuclei were <1%.[
Categorization of Molecular Subtypes
18F-FDG PET/CT Image Technique
18F-FDG PET/CT Image Analysis
The tumors were classified and staged according to
the World Health Organization classification and the
TNM staging system.[
Tumor 18F-FDG PET parameters were compared
with the patient's clinical, immunohistochemistry, and
molecular characteristics. All patients received at least
one therapy protocol. All patients had at least 5 years of
follow-up. Clinical follow-up was performed until the
date of death or the last follow-up date of June 2022
with maximum intervals of 6 months (median follow-
up:30 months, range: 12-90 months).
Statistical Analysis
According to the recommendations of the 12th International
Breast Conference, the patients were categorized
into five subtypes, as follows:[
All patients underwent PET/CT after fasting for at least
6 h and then had their blood glucose levels checked.
A serum glucose level was measured below 200 ng/
dL and intravenous injection of 8?12 mCi (296?444
MBq) (approximately 8.1 MBq of FDG per kilogram of
body weight) 18F-FDG was administered. Whole-body
PET/CT imaging was performed on a biograph (Siemens
Biograph 6, Chicago, IL, USA) using a full-ring
high-resolution (HI-REZ) LSO PET and a six-slice CT
scanner (Siemens Biograph 6, Chicago, IL, USA). Firstly,
a non-enhanced CT scan was performed with the
following parameters: 40?60 mAs, 140 kV, and 5-mm
section thickness. Positron emission tomography scanning with 3 min per bed position was then acquired on
the identical transverse field of view in the caudocranial
direction. PET image datasets were reconstructed iteratively
using the ordered subset expectation maximization
algorithm with CT-based attenuation correction.
Qualitative and quantitative (or semi-quantitative)
image analysis was carried out by two experienced
nuclear medicine specialists with significant experience
in reading 18F-FDG PET/CT scans. All image
analysis was performed using General Electric Advantage
Workstation (AW workstation Volume Viewer 3)
software (GE Healthcare, Waukesha, WI, USA). The maximum intensity projection and attenuation-corrected
PET/CT fusion images were evaluated in three
planes (transaxial, coronal, and sagittal). Maximum
SUV, mean SUV, MTV, and TLG of the tumor and ALN
were recorded. Maximum SUV was based on body
weight and was calculated using the following formula:
(injected dose [MBq] ÷ body weight [g]). The tumor
contours were semi-automatically delineated by using
a threshold of 42% of the SUVmax within the lesion to
calculate MTV. TLG was calculated by multiplying the
SUV mean by the MTV. A volumetric region of interest
was drawn to fully include the primary tumor and/
or ALNs. The volumetric region of interest border was
adjusted semi-automated if the volume extended beyond
the borders of the primary lesion on checking the
sagittal and coronal images.
IBM SPSS Statistics for Windows, version 26 (IBM
Corp. Armonk, N.Y. USA) was used for statistical
analysis. In the evaluation of the study data, descriptive
statistical methods (mean, standard deviation,
median, minimum, and maximum) were applied.
Quantitative evaluations were made using the Shapiro?
Wilk test, Kolmogorov-Smirnov, and graphical
evaluations. Student's t-test was used for two-group
comparisons of normally distributed quantitative
data, and the Mann?Whitney U-test was used for
two-group comparisons of non-normally distributed
data. One-way ANOVA Test was used for comparisons
of normally distributed groups of three or
more; Kruskal?Wallis test was used for comparisons
of non-normally distributed data of groups of three
or more; Bonferroni Dunn test was used for pairwise
comparisons. Pearson Chi-Square test and Fisher-
Freeman-Halton Exact test were used to compare
qualitative data. Spearman's correlation analysis was
used to evaluate the relationships between variables.
McNemar, Kappa concordance test, and diagnostic
screening tests (sensitivity, specificity, PPV, and NPV) were used to evaluate the agreement between ALN biopsy
and ALN SUVmax results. OS rates were calculated
by Kaplan-Meier analysis. Univariable and multivariable
cox regression models were used to investigate
the prognostic factors. Findings that were statistically
significant in univariable analysis were included in the
multivariable backward model. Significance was evaluated
at the p<0.05 level. The primary endpoints were
to evaluate the association between metabolic parameters
obtained from pretreatment 18F-FDG PET/CT
and molecular subtype, immunohistochemistry, and
TNM stage. The secondary endpoint was to determine
OS in female BC patients with IDC.
Out of a total of 179 cases, 137 (76.5%) had positive ALN metastasis on biopsy, while 135 (75.4%) were found to be positive on PET/CT. Of the 42 cases with negative ALN biopsy results, 35 were negative on PET/ CT and 6 were positive. Of the 137 cases with positive ALN biopsy results, 129 were positive on PET/CT and eight were negative. Therefore, the sensitivity of PET/ CT was 94.16%, the specificity was 85.71%, the positive predictive value was 95.56%, the negative predictive value was 81.82%, and the accuracy was 92.18%.
The rate of distant metastasis was statistically higher in the presence of positive ALN compared to negative ALN (36.5% vs. 16.7%, p=0.016). ALNs SUVmax, TLG, and MTV, tumor SUVmax, TLG, and MTV values showed statistically significant differences according to the stage (p=0.001, <0.001, 0.014, <0.001, <0.001, respectively). These values were higher in the advanced stages. MTV values were higher in patients with distant metastasis, ALN metastasis, and involvement of IMLN (p<0.001, p<0.001, p<0.001, respectively).
Tumor TLG value was found to be higher in ER negative and PR negative patients compared to positive ones (respectively, p=0.002, p=0.001). Tumor MTV value was found to be higher in ER negative and PR negative patients compared to positive ones (p=0.039, p=0.007, respectively).
There was no statistical difference between HER2 and nuclear grade with tumor SUVmax and tumor TLG value (p=0.221, p=0.068: p=0.278, and p=0.067, respectively).
There was no statistically significant difference between the rates of distant metastasis according to molecular subtypes (p=0.116). There was no statistical difference between ALN SUVmax and ER status, HER2, and nuclear grade(p=0.838, p=0.810, and p=0.493, respectively). There was no statistical difference between ALN TLG and ER status, PR status, HER2, and nuclear grade. (p=0.465, p=0.068, p=0.771, and p=0.308, respectively). There was no statistical difference between HER2 and tumor SUVmax values (p=0.089).
DM were detected in 57 patients. Tumor SUVmax value was found to be higher in patients with distant metastasis (lymph node, bone, liver, lung, pleura, and brain), ER negative, PR negative, and nuclear Grade III patients compared to their counterparts. (p=0.021, p=0.001, p<0.001, and p=0.014, respectively). Tumor TLG and MTV values were found to be higher in patients with distant metastasis, ALN metastasis, and IMLN involvement (respectively, p<0.001, p<0.001, and p<0.001). Axillary TLG value was found to be higher in patients with DM and ALN metastases compared to those without (p<0.001, p=0.049, and p=0.025, respectively). Axillary SUVmax values were found to be higher in patients with DM and those with negative PR compared to their counterparts (p<0.001, p=0.023, respectively).
According to the TNM classification, 34 patients were Stage I (19%), 69 Stage II (38.5%), 19 Stage III (10.6%), and 57 Stage IV (31.8%).
Forty-five (25.1%) patients died. Out of 45 patients,
36 were Stage IV, 5 were Stage III, and IV were Stage
II. There were two patients with luminal A, 14 patients
with luminal B HER-, nine patients with luminal
B HER+, four patients of HER2+, and 16 patients
of TNBC. The median survival of all patients was 87
months. The 3-year survival rate was 83.8%, the 5-year
survival rate was 70.7%, and the 7-year survival rate
was 64.8% (Fig.
Few studies have investigated the relationship
between the baseline metabolic volume of primary
IDBC measured by 18F-FDG PET/CT scans, molecular
subtype, immunohistochemistry, and OS.
The previous studies have generally assessed all histopathological
subtypes together and have reported
highly variable results.[
The majority of studies have shown that 18F-FDG
uptake, measured by SUVmax, TLG, MTV, and other
parameters, is associated with different molecular
subtypes of BC.[
Our study, along with several other studies,[
The previous studies have pointed out that Ki67 is
positively correlated with 18F-FDG uptake despite its
insignificance.[
ALN metastasis is one of the most important prognostic
factors in BC. There are still conflicting results
regarding the relationship between volume-based
PET/CT parameters of ALN metastasis and the primary
mass. Groheux et al.[
García Vicente et al.[
We detected false negative ALN particularly in the
presence of micrometastatic lymph nodes, similar to
the study conducted by Greco et al.[
Inner tumor location and positive ALN status were
associated with IMN adenopathy. Adam et al.[
In our study, we found that axillary and tumor volumetric
parameters values showed statistically significant
differences according to stage, with higher values
in advanced stages. This finding is consistent with the
study of Kaida et al.[
Tumor size is one of the parameters of TNM staging.
In our study, all volumetric parameters correlated
with the tumor size similar to previous studies.[
In our study, multivariate analysis revealed that
molecular subtype, tumor size, and the presence of
DM were independent prognostic factors that significantly
affected OS. This result is in agreement with
the findings of Jo et al.[
The greatest strength of this study is that there was
a homogeneous cohort of BC patients that included
only female patients with IDC and had a minimum
follow-up period of 5 years. However, this study has
several limitations, such as its retrospective design, the
IHC testing of tumors in various pathology laboratories,
and the inclusion of a cohort of patients with tumors
<2 cm in diameter.
In addition, it is necessary to mention the NCCN
guideline and the indications for the use of 18F-FDG
PET/CT in BC. The NCCN guideline does not recommend
18F-FDG PET/CT in early BC (Stage I, II, or
operable III). 18F-FDG PET/CT is most helpful in situations
where standard staging studies are equivocal or
suspicious, especially in the setting of locally advanced
or metastatic disease.[
Peer-review: Externally peer-reviewed.
Conflict of Interest: All authors declared no conflict of interest.
Ethics Committee Approval: The study was approved by the Okmeydanı Training and Research Hospital Ethics Committee (no: 843, date: 06/03/2018).
Financial Support: None declared.
Authorship contributions: Concept - M.T.; Design - M.T., H.Ö.; Supervision - M.T., H.Ö.; Materials - M.T., H.Ö.; Data collection and/or processing - M.T., H.Ö., P.Ö.N., E.U.; Data analysis and/or interpretation - M.T., H.Ö., P.Ö.N., E.U.; Literature search - M.T., H.Ö., P.Ö.N., E.U., R.E., Ö.T.; Writing - M.T., H.Ö., P.Ö.N., E.U.; Critical review - M.T., H.Ö., P.Ö.N.