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Endocrine therapy as first line and maintenance therapy to patients with
metastatic oestrogen receptor-positive, HER2-negative breast cancer
By: David Söderberg, Medical student
Supervisor: Antonis Valachis, MD, PhD
Assistance: Henrik Lindman, MD, PhD
Date: 2018-08-29
Source: https://pixabay.com/sv/band-symbol-
cancer-mama-br%C3%B6st-rosa-2818640/
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Title: Endocrine therapy as first line and maintenance therapy to patients with metastatic oestrogen receptor-
positive, HER2-negative breast cancer
Innehållsförteckning ....................................................................................................................................................................... 1
Endocrine therapy as first line and maintenance therapy to patients with metastatic oestrogen receptor-
positive, HER2-negative breast cancer .......................................................................................................... 1
Abstract ......................................................................................................................................................... 3
Populärvetenskaplig sammanfattning ............................................................................................................ 4
Bakgrund: ............................................................................................. Fel! Bokmärket är inte definierat.
Metod:................................................................................................... Fel! Bokmärket är inte definierat.
Resultat/diskussion: .............................................................................. Fel! Bokmärket är inte definierat.
Konklusion: .......................................................................................... Fel! Bokmärket är inte definierat.
1. Background: .......................................................................................................................................... 5
2. Methods: ................................................................................................................................................ 6
2.1 Study population: ................................................................................................................................ 6
2.2 Data collection: .................................................................................................................................... 6
2.3 Statistical analyses: .............................................................................................................................. 6
3. Results: .................................................................................................................................................. 7
3.1 Patient, tumour and treatment characteristics ...................................................................................... 7
3.2 Association between CT vs ET in terms of OS, PFS and TTP .......................................................... 10
4. Discussion ............................................................................................................................................ 12
Conclusion ................................................................................................................................................... 13
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Abstract Background: For hormone receptor-positive (HR+), human epidermal growth factor receptor 2
negative (HER2-) metastatic breast cancer the international guidelines suggest endocrine therapy
(ET) as first line treatment, except in case of ‘visceral crisis’. For the latter case, chemotherapy
(CT) is recommended. After CT, maintenance ET or a wait-and-see approach is possible. There are,
however, a lack of robust evidence supporting either. This study is trying to address these two
questions.
Methods: Patients undergoing either endocrine therapy or chemotherapy at Uppsala Academic
Hospital and Mälarsjukhuset during 2008-2015 were selected. Patients had to be oestrogen receptor
positive, HER2-negative and survived at least 3 months from diagnosis. Objective of the study were
to evaluate the time to progression (TTP), progression-free survival (PFS) and overall survival (OS)
according to the type of first line treatment and maintenance endocrine therapy using a propensity
score analysis and inverse propensity score weighting.
Results: Two hundred eighty-five patients were eligible: 234 (82.1%) received ET as first line
therapy, while 51 (17.9%) received CT as first line therapy. Among the latter 36 (70.5%) got a
response on chemotherapy and all received maintenance endocrine therapy. Mean follow up were 37 months
(range 3-118 months). There was no statistical difference between first line treatment; TTP hazard ratio 0.96
(P=0.811, 95% confidence interval [CI] 0.66-1.39), PFS hazard ratio 0.99 (P=0.940, CI 0.69-1.42) and OS
1.19 (P=0.409, CI 0.78-1.78). When using Propensity score and inverse propensity score there were still no
statistical difference.
Conclusion: In this retrospective cohort there were no statistical difference between ET or CT as first line
treatment in terms of TTP, PFS and OS. Maintenance ET was generally used in all patients that responded on
first line CT. In agreement with the international guidelines, endocrine therapy should be the first choice for
first line systemic treatment for luminal A/B metastatic breast cancer in the absence of visceral crisis.
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Populärvetenskaplig sammanfattning
Bakgrund: För hormonreceptorpositiv (HR+), humant epidermal tillväxtfactor receptor 2 negativ
(HER2-) metastaserad bröstcancer föreslår de internationella riktlinjerna att man börjar med
endokrin terapi (ET) som första linjens behandling, förutom i fall det finns tecken till ’visceral kris’.
För det senare är kemoterapi (CT) rekommenderat. Efter CT kan man välja underhållsbehandling
med ET eller en vänta och se strategi. Det finns dock inte tillräckligt med studier som stödjer varken
valet för första linjens behandling som valet av strategi efter CT. Denna studie gjordes för att
undersöka dessa två frågeställningar.
Metod: Patienter som undergick antingen ET eller CT på Uppsala Akademiska Sjukhus och
Mälarsjukhuset i Eskilstuna mellan 2008 till och med 2015 ingick i studien. Inklusionskriterierna
var östrogenreceptorpositiv, HER2-negativ metastaserad bröstcancer, som överlevde minst 3
månader efter metastasdiagnos. Målet med studien var att undersöka skillnaden mellan ET och CT
som förstalinjens behandling i form av Tid till progression (TTP), Progressionsfri överlevnad (PFS)
och Total överlevnad (OS). Vi använde oss av en propensity score analysis och en inverse
propensity score weighting.
Resultat: 285 patienter passade in i inklusionskriterierna: 234 (82.1%) fick ET som första linjes
behandling medan 51 (17.9%) fick CT som första linje. Av den senare gruppen fick 36 (70.5%)
patienter en respons på CT och alla dessa fick senare underhållsbehandling med ET. Den
genomsnittliga tiden som patienten följdes var 27 månader (spann 3-118 månader). Det återfanns
ingen statistisk signifikant skillnad mellan förstalinjens behandlingsalternativ; TTP hazard ratio
(HR) 0.96 (P=0.811, 95% konfidens intervall [CI] 0.66-1.39), PFS HR 0.99 (P=0.940, CI 0.69-1.42)
och OS HR 1.19 (P=0.409, CI 0.78-1.78). Vid sensitivitets analyserna sågs fortfarande inga
skillnader.
Konklusion: Denna retrospektiva kohortstudie hittade inga statistiska signifikanta skillnader mellan
ET och CT som första linjens behandling i form av TTP, PFS och OS. Underhållsbehandling med
ET användes hos alla patienter som fick respons på första linjens CT. I linje med internationella
rekommendationer är det rimligt att endokrin terapi bör vara första valet som första linjes
behandling för HR-positiv, HER2- negativ metastaserad bröstcancer vid avsaknad av ’visceral kris’.
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1. Background:
In Sweden, breast cancer (BC) is the most common cancer in women, measuring up to 14,6 % of
all cancers in both men and women.1 With over 7 500 new diagnosed patients and almost 1 400
women deaths, it is the third cause of cancer-related deaths in Sweden 2016.2,3
The main cause of breast cancer-related deaths is the act that metastatic breast cancer (MBC) is
“incurable” with the treatment options that exists today. It is estimated that around 6% of patients
have metastatic disease at the time of diagnosis and 20% to 50% with primary breast cancer will
develop a metastatic disease later in life.4
There are four main molecular subtypes of breast cancer, and up to 21 distinct histological
subtypes, that has their own prognosis and available treatments. Hormonal receptor (HR) status and
human epidermal growth factor receptor 2 (HER2) status are the two predictive factors that
influence the treatment strategy in patients with breast cancer.
Luminal A (71%) subtype has oestrogen receptor (ER) and/or progesterone receptor (PR)
positivity (+) and HER2 negativity (-) as well as a low Ki67 (a proliferation indicator) and is the
most common and less aggressive than other subtypes.
Luminal B (12%) subtype is ER+ and/or PR+ as well as either HER2+ or a high Ki67 and are
associated with a poorer survival than luminal A.
Triple negative (12%) subtype is ER-, PR- and HER2- and has a poorer prognosis than the other
subtypes.
HER2-enriched (5%) subtype is ER-, PR- and HER2+ and tends to grow and spread more
aggressively than other subtypes.5
In patients with Luminal A or B MBC, there are two treatment options as first line: chemotherapy
(CT) or Endocrine Therapy (ET). The choice of which line to start with is influenced by but not
limited to tumour burden, biological age, comorbidities, menopausal status and patients’
preferences. The European Society for Medical Oncology recommends starting with ET in most
cases whereas CT is recommended in case of visceral crisis where rapid response to oncological
treatment is necessary.6 When choosing CT as the first line treatment, it is recommended to use ET
as maintenance therapy until disease progression. However, the expert panel recognised the lack of
robust evidence behind this recommendation because the meta-analysis that lies behind the currents
recommendations included studies that used outdated systemic oncological therapies and did not
exclude patients with unknown/negative ER-status. 7
The aim of this retrospective study was to investigate whether there is a difference to time to
progression (TTP), progression-free survival (PFS), or overall survival (OS) between the two
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treatment options, namely ET or CT as first line treatment in patients with MBC of Luminal
subtype and whether maintenance ET could offer a benefit in prognosis compared to treatment
pause after first line CT.
2. Methods:
2.1 Study population:
The cohort included patients who had undergone treatment for MBC diagnosed between 2008 to
2015 at Uppsala Academic Hospital and Mälarsjukhuset in Eskilstuna, Sweden. The patients in
Uppsala where extracted from the database Real-Q whereas the patients in Eskilstuna where
extracted from the database MOSAIQ oncology information system. After identifying the patients,
data were gathered from the databases and patient records.
The inclusion criteria included ER+ and/or PR+, HER2- metastatic breast cancer in a palliative
setting, with a cut-off in survival for at least three months after diagnosis to exclude patients with
rapid disease progression and aggressive tumour biology in whom the oncological treatment would
be meaningless irrespectively the type of treatment given.
2.2 Data collection:
Data were collected about the following parameters: age at diagnosis, comorbidities (Charlson
comorbidity index), date for diagnosis, ER-status, PR-status, Ki67, histological grade, HER2-status,
type of primary surgery, adjuvant treatment, date for relapse, location of metastasis, bone-only
metastasis, number of metastatic sites, performance status at the start of oncological treatment, type
of 1st to 4th line of treatment; Response to the treatment (complete remission, partial remission,
stable disease, progressive disease), date for the start and the end of each treatment line, reason for
the switching treatment, date of death and cause of death.
Outcomes and definitions:
TTP was defined as the time from treatment initiation until disease progression, PFS was defined
as the time from treatment initiation until either disease progression or death due to any cause. OS
was defined as the time from treatment initiation until death for any reason. The cut-off date for the
whole cohort was 1st of May 2018. Luminal B was defined as either a Ki67 >20% or Ki67 >14%
and PR <20%. All tumours that did not meet the criteria for Luminal B disease were classified as
Luminal A.8
2.3 Statistical analyses:
Categorical variables were summarized by the number and percentage of patients in each
category. Continuous variables were summarized by mean, median, minimum and maximum
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values.
For the bivariate analyses between variables, chi-square test for categorical variables and t-test or
Mann-Whitney U-test (depending on the distribution of the variable) for continuous variables were
used.
For the time-to-event outcomes (TTP, PFS, OS) the potential association between groups in
comparison first line CT vs. first line ET was assessed by the Kaplan-Meier method (log rank test
for statistical significance). In addition, multivariable Cox proportional hazards model was created
after adjustment for the following variables: age, breast cancer intrinsic subtype (Luminal A-like vs.
luminal B-like), de novo metastasis (yes vs. no), performance status (0-1 vs. 2-3), presence of
visceral metastases (yes vs. no), liver metastases (yes vs. no), bone-only metastases (yes vs. no).
Two propensity score methods, namely the inverse propensity score weighting and the propensity
score adjustment regression was used as sensitivity analyses for the comparison CT vs. ET.
Specifically, a logistic regression propensity score model of the type of first line treatment was
created using the same variables used in the cox proportional hazard model.
All reported P values of statistical tests are two-tailed and P<0.05 was taken to be statistically
significant. All analyses will be performed using the SPSS.
3. Results:
3.1 Patient, tumour and treatment characteristics
In total, 612 patients were identified, 144 in Mälarsjukhuset and 468 in Uppsala Academic
Hospital, which resulted in 285 eligible patients (Figure 1). The most common reason for exclusion
was either a diagnosis outside the enrolment dates or HER2+. The mean follow up was 37 months
(range 3-118 months).
The median age at first diagnosis and at recurrence was 61 (range 31-88) and 68 (range 35-94),
respectively. There was a difference between patients receiving ET and CT as first line therapy
when looking at age at recurrence, 69 (range 35-94) and 62.5 (range 37-81) respectively, with a P-
value <0.001. Charlson comorbidity index had a median of 2 (range 0-7), with a difference between
ET (3, range 0-7) and CT (2, range 0-6) with a P-value
<0.001. Primary tumour characteristics are summarized
in Table 1A and the treatment for the primary tumour is
summarized in table 1B. The differences in initial
tumour characteristics between ET vs CT as first line
treatment are shown in the tables.
Ki67 had a median of 23% (range 1-90) for the
primary tumour pathological anatomical diagnosis Figure 1: cohort identification
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Overall ET as 1st CT as 1st p-value
N (%) N (%) N (%)
Primary tumour characteristics N=285 N=234 N=51
Histology
Ductal
181 (63.5)
147 (68.1)
34 (69.4)
0.439 Lobular 77 (27) 62 (28.7) 15 (30.6)
Other 7 (2.5) 7 (3.2) 0 (0)
Missing 20 (7)
Tumour stage
I 47 (16.5) 42 (22.5) 5 (11.4)
0.287
II 27 (9.5) 23 (12.3) 4 (9.1)
III 86 (30.2) 68 (36.4) 18 (40.9)
IV 71 (24.9) 54 (28.9) 17 (38.6)
Missing 54 (18.9)
Elston-ellis grade
I 22 (7.7) 18 (11.0) 4 (9.1)
0.398 II
123 (43.2)
100 (61.0)
23 (52.3)
III 63 (22.1) 46 (28.0) 17 (38.6)
Missing 77 (27)
Progesterone receptor positivity
Yes
190 (66.7)
149 (63.4)
41 (82.0) 0.011
No 95 (33.3) 86 (36.6) 9 (18.0)
Histological subtype
Luminal A
124 (43.5)
100 (56.5)
24 (52.2)
0.599 Luminal B 99 (34.7) 77 (43.5) 22 (47.8)
Missing 62 (21.8)
Metastasis at diagnosis
Yes 71 (24.9) 54 (23) 17 (34)
0.102
No
214 (75.1)
181 (77) 33 (66)
Tabell 1A: Primary tumour characteristics
Overall ET as 1st CT as 1st p-value
N (%) N (%) N (%)
Metastatic site N=285 N=234 N=51
Bone-only 101 (35.4) 90 (38.3) 11 (22.0) 0.029
Visceral 72 (25.3) 51 (21.7) 21 (42.0) 0.003
Pulmonary 85 (29.8) 72 (30.6) 13 (26.0) 0.515
Liver 63 (22.1) 46 (19.6) 17 (34.0) 0.026
Central nervous system 4 (1.4) 3 (1.3) 1 (2.0) 0.540
No of metastatic sites, median (range) 1 (1-4) 1 (1-4) 2 (1-4) 0.122
Biopsy at recurrence 141 (49.5) 114 (48.5) 27 (54.0) 0.481 Tabell 2: Metastatic site at metastasis diagnosis
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Overall ET as 1st CT as 1st p-value
N (%) N (%) N (%)
Treatment of primary tumour N=285 N=234 N=51
Type of surgery
No surgery 36 (12.6) 33 (14.2) 3 (6.0) 0.338
Breast conserving 112
(39.3) 93 (39.9) 19 (38.0)
Mastectomy 134 (47) 106
(45.5) 28 (56)
Missing value 3 (1.1)
Lymph node surgery
Sentinel node biopsy 26 (9.1) 23 (9.9) 3 (6.0) 0.430
Axillary node dissection 212
(74.4)
170
(73.0) 42 (84.0)
No surgery 44 (15.4) 39 (16.7) 5 (10.0)
Missing value 3 (1.1)
Adjuvant radiotheraphy
No radiotherapy 119
(41.8) 98 (41.9) 21 (42.0) 0.945
Breast only 75 (26.3) 61 (26.1) 14 (28.0)
Breast and lymph nodes 90 (31.6)
75 (32.1) 15 (30.0)
Missing value 1 (0.4)
Adjuvant chemotherapy
No chemotherapy 182
(63.9) 152
(64.7) 30 (60.0) 0.805
Anthracyclines and Taxanes 57 (20)
46 (19.6) 11 (22.0)
Anthracyclines only 35 (12.3) 29 (12.3) 6 (12.0)
Other 11 (3.9) 8 (3.4) 3 (6.0)
Adjuvant Endocrine therapy
No therapy 111
(38.9) 86 (36.8) 25 (50.0) 0.176
Aromatase inhibitors (AI) 45 (15.8)
37 (15.8) 8 (16.0)
Tamoxifen 73 (25.3) 65 (27.8) 7 (14.0)
Tamoxifen and AI sequentially 56 (19.6)
46 (19.7) 10 (20.0)
Missing value 1 (0.4) Tabell 1B: Primary tumour treatment
that most patients received adjuvant ET and/or radiotherapy after radical surgery, not including
primary metastasized patients. Overall 20 patients were pre/perimenopausal at recurrence, standing
for 7.0% of all patients.
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The metastatic sites are summarized in
table 2, including biopsy frequency at
recurrence. The treatment received, PS,
best response during a treatment line and
reason for discontinuation is summarized
in table 3. It was shown that most patients
(n=234, 82.1%) received ET as first line
treatment, and of which Aromatase
inhibitors was most commonly used
(n=181, 77.4%).
In all treatment-lines except the fourth there was more patients who received ET than CT. All
patients that responded on CT received maintenance ET (n=36, 70.6%). Figure 2D shows best
treatment results in a graph.
3.2 Association between CT vs ET in terms of OS, PFS and TTP
The Kaplan Meier curve for TTP (figure 2A), PFS (figure 2B) and OS (figure 2C) show that there
was no statistically significant difference between getting ET or CT as first line treatment (p=0.557,
p=0.653 and p=0.850 respectively). When using the cox regression analysis, it was shown that there
is no statistically significant difference between ET and CT in terms of TTP, PFS and OS. The same
Figure 2A-D: Kaplan Meier curve and treatment response
Table 3: Treatment after metastasis and treatment results
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result was shown when using propensity score adjustment regression and inverse propensity score
weighting.
In the Cox regression analysis (Table 4A-C), having a metastasis at first diagnosis (de novo) was
shown to have hazard ratio (HR) of 2.10 for time to progression (p=<0.001, confidence interval
95% (CI), 1.39-3.23). In addition, a luminal A primary tumour was shown to be associated with a
longer TTP compared to luminal B subtype with a hazard ratio of 0.64 (P=0.003, CI 0.48-0.86)
compared to luminal B.
Similar result traits were shown for PFS with de novo metastasis HR 2.25 (p=<0.001, CI 1.48-3-
41) and luminal A primary tumour HR 0.66 (P=0.004, CI 0.50-0.88).
For OS it was shown that visceral metastasis had a HR 3.40 (P=0.005, CI 1.45-8.00). De novo
metastasis HR 2.41 (P=0.001, CI 1.47-3.95) and Luminal A primary tumour HR 0.58 (P=0.001, CI
0.42-0.81) results traits that were similar to both TTP and PFS.
P-value
Hazard ratio
Lower 95,0 % CI
Upper 95,0 % CI
De novo vs. Recurrence <0.001 2.10 1.39 3.23
Luminal A vs B 0.003 0.64 0.48 0.86
Bone-only metastasis 0.052 0.72 0.51 1.02
Precence of viceral metastasis 0.138 1.82 0.82 4.02
Age at recurrence 0.003 0.98 0.97 0.99
Presence of liver metastasis 0.636 1.21 0.55 2.69
Performance status (0-1 vs 2-4) 0.364 0.78 0.46 1.33
Type of 1st line Theraphy (CT vs ET) 0.811 0.96 0.66 1.39
CT vs. ET (propensity score adjustment regression) 1.08 0.74 1.57
CT vs. ET (inverse propensity score weighting) 1.19 0.80 1.77
P-value
Hazard ratio
Lower 95,0 % CI
Upper 95,0 % CI
De novo vs. Recurrence <0.001 2.25 1.48 3.41
Luminal A vs B 0.004 0.66 0.50 0.88
Bone-only metastasis 0.069 0.74 0.54 1.02
Precence of viceral metastasis 0.075 1.98 0.93 4.18
Age at recurrence 0.041 0.99 0.98 1.00
Presence of liver metastasis 0.445 1.34 0.63 2.87
Performance status (0-1 vs 2-4) 0.431 0.81 0.48 1.36
Type of 1st line Theraphy (CT vs ET) 0.940 0.99 0.69 1.42
CT vs. ET (propensity score adjustment regression) 1.05 0.73 1.51
CT vs. ET (inverse propensity score weighting) 1.07 0.73 1.58
Table 4A: Cox regression analysis for time to progression
Table 4B: Cox regression analysis for progression-free survival
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P-value
Hazard ratio
Lower 95,0 % CI
Upper 95,0 % CI
De novo vs. Recurrence 0.001 2.41 1.47 3.95
Luminal A vs B 0.001 0.58 0.42 0.81
Bone-only metastasis 0.448 0.86 0.59 1.26
Precence of viceral metastasis 0.005 3.40 1.45 8.00
Age at recurrence 0.091 1.01 1.00 1.03
Presence of liver metastasis 0.073 2.20 0.93 5.19
Performance status (0-1 vs 2-4) 0.663 0.87 0.50 1.53
Type of 1st line Theraphy (CT vs ET) 0.409 1.19 0.78 1.78
CT vs. ET (propensity score adjustment regression) 0.88 0.58 1.33
CT vs. ET (inverse propensity score weighting) 0.83 0.53 1.29
4. Discussion
Our results show that there is no statistically significant impact on TTP, PFS or OS between
receiving CT versus ET as first line treatment in a cohort of luminal breast cancer patients. An
aggressive primary tumour (luminal B) had a negative impact on TTP, PFS and OS as well as the
presence of de novo metastatic disease.
What we could see concerning maintenance ET was that all patients who responded on first line
CT received ET afterwards. This observation shows that the clinical practice is to give maintenance
ET instead of a treatment break in these two institutes and might reflect the treatment tradition for
patients with luminal metastatic breast cancer in Sweden in general.
Our results are in accordance with prior studies on this topic. Bonotto et al.9 showed similar
results, with no impact on OS between CT vs. ET after matching for covariates. Song et al10 also
showed no significant impact on OS between CT vs. ET when adjusting for baseline covariates. In
the largest study investigating this research question so far by Jacquet et al.11 the authors concluded
that there was no significant difference on OS and PFS between CT vs. ET. Considering the lack of
difference in survival between ET and CT in these patients and the fact that ET has better
tolerability than CT, it is reasonable to offer ET as first line treatment.
Maintenance ET is a reasonable option in responding patients,12,13,14 and with our result, it could
be hard to find enough patients who have a treatment break after first line CT to perform a study
with adequate power. This observation could be useful for research funders when studies on this
breast cancer population are planned because the tradition of using ET maintenance in all patients
can influence the potential eligible population as well as the expected survival.
The retrospective and observational study format is two of the limitations of this study, although
our results is in line with newly published data which is in favour to its validity. A small study
cohort is also a limitation that we had to regard, as well as the limitation that all data were collected
Table 4C: cox regression analysis for overall survival
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using electronic medical records where not all data could be found sometimes leaving missing
values. Another limitation was the fact that we were unable to investigate the role of maintenance
ET after first line CT because all patients that responded to CT received maintenance ET as well.
Further studies should be concentrated in investigating the potential role of new treatment options
such as CDK 4/6 inhibitors in the clinical question of CT vs. ET in patients with MBC. Considering
the fact that all the studies of ET vs. CT included patients before the CDK 4/6 inhibitor era and the
positive effect of the combination of CDK 4/6 inhibitor with ET compared to ET alone15, one could
argue that this combination therapy could offer a survival advantage compared to chemotherapy.
Conclusion
Our results suggest a similar prognosis between CT and ET as first line therapy in patients with
MBC of Luminal subtype, supporting the use of ET as a first line treatment considering the better
tolerability profile than CT. Although, no conclusion about the efficacy of maintenance ET can be
drawn from this study, our study found that the clinical practice in Sweden seems to be to use
maintenance ET instead of a watch-and-wait approach after first line CT, an observation that could
have an impact in the design of future MBC studies in Sweden.
__________________________________________________________________________________
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