METHODS
The study included 209 patients with invasive BC at the time of initial diagnosis. Patients underwent
whole-body 18F-fluorodeoxyglocose positron emission tomography/computed tomography
and breast magnetic resonance imaging including diffusion weighted imaging. Histologic grade
(HG), histological type, human epidermal growth factor 2 (HER-2), Ki-67, estrogen receptor (ER),
and progesterone receptor (PR) markers of the breast tumor were evaluated in pathological samples.
Tumor-node-metastasis (TNM) staging was performed based on clinical, pathological, and
imaging findings.
RESULTS
HER-2 positivity and PR positivity demonstrated a strong correlation with distant metastasis (p=0.00040
ve 0.00045). ER positivity was positively correlated with SUVmax (p=0.0001) and SUVmax/ADCmean
(p=0.006). PR was positively correlated with ADCmean (0.028). SUVmax was correlated with the tumor size
(p=0.008), TNM stage (p=0.022 and r=0.159), and HG (p<0.0001 and r=0.347).
CONCLUSION
Both SUVmax and ADCmean are helpful parameters in determining prognosis in BC. HER-2 and PR
positivity, and tumor size can be used as revealing and useful parameters in determining distant
metastases.
Keywords: Apperent diffusion coefficient; breast cancer; diffusion-weighted magnetic resonance imaging; positron emission tomography
18F-FDG positron emission tomography/computed
tomography (18F-FDG-PET/CT) and diffusion-weighted
image (DWI) are imaging methods that give indirect
information of the biological properties of cancer.
Apparent diffusion coefficient (ADC) and maximum
standardized uptake value (SUVmax) values measured
from breast mass have the potential to be used as prognostic
biomarkers.[
DWI is an magnetic resonance imaging (MRI) technique
based on thermal energy-dependent random
movements (Brownian motion) of water molecules
in biological tissues, and its quantitative parameter is
ADC. In high cellular malignant tissue, low ADC values
are expected due to restricted fluid diffusion in the
relatively decreased extracellular space and an increase
in the nucleus/cytoplasm ratio.[
18F-FDG-PET/CT is a widely used diagnostic
method in the diagnosis, systemic staging, detecting
recurrence and evaluation of response to treatment, as
well as distinguishing malignant from benign lesions,
which enables image acquisition by using high glucose
metabolism in cancer cells and therefore increased
FDG uptake.[
Many biological factors, including molecular subtypes,
histologic grade (HG), estrogen receptor (ER),
progesterone receptor (PR), human epidermal growth
factor receptor 2 (HER-2), and Ki-67 and also age and
axillary lymph node (LN) involvement, have been used
to determine the prognosis.[
Studies are showing that ADC[
18F-FDG-PET/CT
All the patients were imaged using an FDG-PET/CT
scanner with 16-multi-detector CT (mCT 20 ultra HD
LSO PET/CT, (Siemens molecular imaging, Hoffmann
Estates, Illinois, USA).
Patients were fasted for at least 6 h before the PETCT procedure and all the patients" blood glucose levels measured below 150 mg/dL. All patients were administered intravenously with 18F-FDG radiopharmaceutical, calculated from 0.15 mCi/kg based on their body weight. Following the injection, the patients were rested in the half-lying position for 50-60 min in a silent room. At the end of the rest period, combined image acquisition began unenhanced CT scan (3.5 mm slice thickness, 120 kV tube and up to 80 mA s) and subsequent 3D mode PET scan (5-7 bed positions, 3 min per bed position) between vertex and upper femur at the supine position.
1.5-Tesla Breast MRI
The MRI were acquired in the prone position, using a
1.5-Tesla scanner (Signa HDi; GE Healthcare, Milwaukee, WI) with a dedicated bilateral breast phased-array
coil. Before the examination, a catheter was placed
through the antecubital vein to the patients. Standard
protocol with contrast and DWI sequence was used in
all examinations.
MR imaging protocol included axial, coronal, and sagittal turbo spin-echo T2 weighted (3D) sequence with 2 mm slice thickness and 1 mm slice spacing, axial fat-suppressed T2 sequence with slice thickness 2 mm and slice thickness 3 mm (fat suppression technique was the short-tau inversion recovery), axial DWI sequence with single-shot EPI; b value = 0 and 800 s/mm2 with 3 mm slice thickness and slice spacing; after pre-contrast T1-weighted axial 3D dynamic gradient echo fat suppressed images, a bolus of 0.1 mmol/L per kilogram of body weight contrast agent gadoterate meglumine and 20 mL saline injection was administered with an automated contrast injector. In the post-contrast phase, six phased axial T1-weighted 3D dynamic gradient-echo fat-suppressed consecutive serial images were obtained with a maximum of 60-second intervals. Post-processing, maximum-intensity projection, subtraction, and ADC maps were obtained. All lesions were seen and evaluated at MRI.
Imaging Analysis
All 18F-FDG-PET/CT images were analyzed by two
nuclear medicine physicians with 5 and 10 years of experience
in PET/CT. The readers were blinded to the
histopathologic diagnosis and had any knowledge of
other quantitative imaging data. The volume of interest
(VOI) was determined as the area where FDG uptake
was most intense on the relevant primary breast tumor,
and FDG uptake was semiquantitatively analyzed
in this area. SUVmax was considered the voxel with the
highest SUV in the VOI examined and was used to
measure and record uptake.
Two radiology physicians with 5 and 12 years of experience in breast MRI evaluated ADC maps retrospectively. The readers had no knowledge of histopathologic diagnosis and quantitative imaging data. On the ADC map, multiple uniform circular 20 mm2 region of interests placed within the primary breast tumor. ADC measurements were made only from a solid portion of the tumor and dynamic contrast-enhanced images were used as a reference to avoid measuring from cystic, hemorrhagic, or necrotic areas. The average of the ADC values was calculated and noted as ADCmean.
Figures
ER: Estrogen receptor; PR: Progesterone receptor; HER-2: Human epidermal growth factor receptor 2; 18F-FDG-PET/CT: 18F-FDG positron
emission tomography/computed tomography; SUV: Standardized uptake value.
ADC: Apparent diffusion coefficient.
Histological Evaluation
In all patients, first the histological grade (HG) and
type of the tumor were determined in the pathology
specimens obtained by core needle biopsy or surgery.
Subtyping was made according to the markers ER, PR,
HER-2, and Ki-67 with immunohistochemical tests.
The ER and PR results were determined to be positive
according to the proportion of positively stained
cell nuclei was higher than 10% and negative when
less than 10%. HER-2 expression was determined with
fluorescence in situ hybridization. Score +2 and +3 are
defined as positive. If the Ki-67 proliferation index
was over 15%, it was considered positive and below
15% was considered negative. LN status was evaluated
mainly with the imaging techniques and also fine-needle
aspiration and sentinel LN biopsy. TNM staging of
all the patients was evaluated with initial imaging, biopsy,
and pre-treatment clinical staging.
Statistical Analysis
Statistical analyzes were performed using IBM SPSS
Statistics 25.0 (Armonk, NY: IBM Corp.) package program.
Normality assumption of quantitative data was
checked by Shapiro-Wilk test. Since the normality assumption
was not provided, the Mann-Whitney U test
and the Kruskal-Wallis test were used for assessing the
relationship between SUVmax, ADCmean, SUVmax/ADC
values, and the clinicopathological parameters. Dunn
test for pairwise comparison and Bonferroni correction
was applied to the results. Correlation of quantitative
data with each other (SUVmax, ADC, SUVmax/
ADC) or with HG and clinical stage was evaluated with
Spearman"s Rho correlation coefficient. Logistic regression
analysis was used to develop a model that can predict
the presence of distant metastasis in the patient
with prognostic factors and imaging data, variables
with p<0.10 in univariate logistic regression analysis
and variables considered to be clinically significant
were evaluated by multiple logistic regression analysis.
Comparison of Groups According to the Presence
of Distant Metastasis
In the comparison of metastatic and non-metastatic
groups, clinicopathologic factors and quantitative
imaging data were compared in univariate analysis,
and those with p<0.1 were evaluated by logistic regression tests in multivariate analysis. Tumor size, HER-2
overexpression, and PR positivity were determined as
independent variables affecting the presence of metastasis
in multivariate analysis (Table
Distant metastasis was present in 83 (39.7%) of the
patients. There was no significant difference in mean
age, histopathological diagnosis, HG, ADCmean, SUVmax,
SUVmax/ADCmean, and molecular subtypes between
metastatic and non-metastatic groups (p>0.05). The
distribution of ADCmean, SUVmax ve SUVmax/ADCmean
values of the metastatic and non-metastatic groups did
not differ significantly (p>0.05) (Table
Univariate analysis showed that a large tumor size
(>2 cm) was significantly correlated with the presence
of distant metastasis (p<0.005). Immunohistochemistry
receptor positivity was present for HER-2, ER, and PR and p values between metastatic and nonmetastatic
groups were p=0.0004, 0.803, and 0.00045,
respectively. HER-2 positivity and PR positivity
demonstrated a strong correlation with distant metastasis.
There was no difference for molecular subtypes
(luminal A, luminal B, triple-negative, and HER2)
and a high Ki-67 index between metastatic and nonmetastatic
groups (Table
Correlation of SUVmax and ADCmean
The mean SUVmax, ADCmean, and SUVmax/ADCmean
values were 12.16±8.54 (range, 1.6-52.5),
962±206×10-6 mm2/s (range, 464-1980×10-6), and
0.13±0.009, respectively. There was no correlation
between ADCmean and SUVmax (correlation coefficient
r=-0.017, p=0.805).
Relationships between Prognostic Factors,
SUVmax, ADCmean and SUVmax/ADCmean
Univariate analysis showed that SUVmax and SUVmax/
ADCmean were significantly correlated with large tumor
size (p=0.008 and p=0.002), Ki67 status (p<0.0001,
p<0.0001). In terms of hormone receptor status; ER
positivity was positively correlated with high SUVmax
(p=0.0001) and SUVmax/ADCmean (p=0.006). PR was
positively correlated with ADCmean (0.028). HER-2
positivity had no significant correlation (p>0.1) with
SUVmax and ADCmean (Table
The relationships between clinical stage and HG,
ADCmean, SUVmax, and SUVmax/ADCmean were evaluated
with Spearman's Rho coefficient. SUVmax and
SUVmax/ADCmean had a positive significant association
with the clinical stage (p=0.022 and r=0.159)
and HG (p<0.0001 and r=0.347) (Fig.
HG: Histologic grade; ADC: Apparent diffusion coefficient;
SUV: Standardized uptake value.
Relationships between SUVmax and ADCmean
In the study of Baba et al.[
Relationships between SUVmax and Prognostic
Factors
IDC is the most common type of invasive BC and the
second most common tumor type is ILC. We observed a
significant difference between SUVmax of the two groups
of histologic types in line to previous studies.[
Higher SUV values were seen in tumors with a
triple-negative hormonal profile in the current study,
a finding consistent with the previous studies.[
Ki-67 proliferation index is a marker of high mitotic
activity and is useful for evaluating the degree of cellularity.
Our study confirms a highly significant positive
relationship between Ki-67 and enhanced glycolysis as
determined by the measure of SUVmax, as observed previously.[
Axillary LN positivity was not correlated with SUVmax
. This finding was consistent with a previous study[
Relationship between ADC and Prognostic
Factors
In our study, we found a significant association between
the low ADC values and ER positivity which is consistent
with many of the previous studies.[
Ipsilateral axillary LN metastasis is the main predictor
of long-term survival.[
Factors Affecting the Presence of Metastasis
Tumor size is a well-known and important prognostic
factor of BC and increasing size of the breast
tumor is associated with high metastatic potential and
decreased overall survival.[
The majority of BC cases are of the luminal-A subtype,
which are hormone receptor-positive tumors (ER
and/or PR) and these types of tumors are sensitive to
hormonal therapies. However, cases with luminal BC
constitute the majority of patients with distant metastases
at the time of diagnosis and are frequently incurable.
Recent studies revealed that invasiveness and metastasis
of luminal BC are supported by the two isoforms of
PR (PR-A and PR-B), in two different pathways. As a result of these studies, PR-A has the main responsibility
in promoting invasiveness and metastasis by suppressing
estrogen/ER action. Overexpression of PR-A
is associated with increased invasiveness of BC and
decreased disease-free survival.[
HER-2 oncoprotein is responsible for cancer development
by stimulating cell proliferation. HER-2 also
increased angiogenesis through up-regulation of vascular
endothelial growth factor (VEGF) and increasing microvascular density of the tumor accompanied
by increasing invasion and metastasis.[
SUVmax/ADCmean is a combination of these parameters
and it was more accurate than either SUVmax and ADCmean for demonstrating the relationships with prognostic
factors. SUVmax/ADCmean was previously used in
the study of Baba et al.[
This study has some limitations. First, it was performed
retrospectively in a single institution. Second, metastases were evaluated only at the time of diagnosis, and
metastases developed during treatment and maintenance
were not evaluated due to the short follow-up period.
Third, since FDG-PET/CT is only applied to advanced-
stage BC patients in our center, the number of
early-stage patients was relatively low.
Our study with 209 invasive BC showed no correlation
between SUVmax and ADCmean. Similar to our study,
many of the studies evaluating this relationship were
also found no correlation between ADCmean and SUVmax.
[
In our study, the relationships between SUVmax and
ADCmean values of primary breast tumor and clinicopathological
prognostic factors were evaluated. We
observed that high SUVmax was correlated with tumor size, ER, Ki-67, high HG, advanced TNM stage, histological
subtype, and molecular subtype. These results
are similar to previously published studies; SUVmax
had a positive correlation with tumor size and high
HG.[
In many studies comparing ADC in malignant and
benign lesions of the breast, significantly lower ADC
values and diffusion restriction were observed in malignant
lesions. In vivo, perfusion is also important factor
as microscopic motion that affects ADC. Increasing
microvessels due to tumor angiogenesis in malignant
lesions may cause an increase in ADC due to the perfusion
effect.[
In our study, tumor size, HER-2 overexpression, and PR
positivity were determined as independent variables affecting
the presence of metastasis in multivariate analysis.
Peer-review: Externally peer-reviewed.
Conflict of Interest: All authors declared no conflict of interest.
Ethics Committee Approval: The study was approved by the University of Health Sciences İstanbul Training and Research Hospital Clinical Research Ethics Committee (no: 2279, date: 08/05/2020).
Financial Support: None declared.
Authorship contributions: Concept - K.E.Ç., M.A.N.; Design - K.E.Ç., M.A.N.; Supervision - M.B.U., E.A.; Funding - K.E.Ç., M.A.N.; Materials - K.E.Ç., M.A.N.; Data collection and/or processing - K.E.Ç., M.A.N.; Data analysis and/ or interpretation - K.E.Ç., M.A.N., M.B.U.; Literature search - K.E.Ç., M.A.N., M.B.U., E.A.; Writing - K.E.Ç., M.B.U.; Critical review - E.A.