Introduction
The survival rate of cancer patients has been steadily rising over the past decades
due to optimisation and efficiency of oncological therapy concepts [1].
Cancer is predominantly a disease of the older person, whereas adolescents and young
adults are relatively rarely affected by it. In Germany, currently about 15 000 patients
aged between 15 and 39 years are taken ill with cancer each year, with a total of
480 000 new cases [2]. Within this age range of under forties, breast cancer is the one most common form
of cancer in Germany, with approx. 2500 new cases each year [2], [3]. In the age group of under 45-year-olds, the incidence in Germany from 2011 – 2012
was 120/100 000 [4]. Many of these women have not yet completed their family planning, due to, amongst
other reasons, the rising age of the women when their first child is born [6].
In young breast cancer patients, tumour biology commonly shows an aggressive growth
pattern and is associated with a poor prognosis [7]. For this reason, polychemotherapy – usually in a neoadjuvant setting – is an important
therapy measure, particularly in young patients with breast cancer.
Focus is shifting to the long-term effects of oncological therapy, particularly in
the light of the ever later realisation of the desire to have children. Premature
ovarian failure (POF) is a common consequence of chemotherapy treatment. This cytotoxicity
is reversible in organs with a high cell division rate, such as bone marrow, gastro-intestinal
tract or thymus, for example. The ovaries, on the other hand, are damaged by chemotherapy
to varying degrees because of their limited number of cells with no potential for
replication or regeneration of the follicles [8], [9]. This can result in permanent infertility of the affected women, see [Tables 1] and [2].
Table 1 Amenorrhoea rates after chemotherapy in premenopausal patients with breast cancer,
overview, taken from [13].
|
Age (years)
|
Chemotherapy
|
Amenorrhoea rate (%)
|
|
A = doxorubicin; C = cyclophosphamide; E = epirubicin; F = 5-fluorouracil; M = methotrexate
|
|
> 40
|
6 × CMF, 6 × FEC, 6 × FAC
|
> 80 (high risk)
|
|
< 40
|
EC (dose dense)
|
|
|
30 – 39
|
6 × CMF, 6 × FEC, 6 × FAC
|
20 – 80 (moderate risk)
|
|
> 40
|
4 × AC
|
|
|
< 30
|
6 × CMF, 6 × FEC, 6 × FAC
|
< 20 (low risk)
|
|
< 40
|
4 × AC
|
|
Table 2 Amenorrhoea rates after chemotherapy in premenopausal patients with breast cancer,
selected studies [14], [15], [16].
|
Chemotherapy
|
Age (years)
|
Number of patients
|
Amenorrhoea rate (%)
|
Study
|
|
EC = epirubicin, cyclophosphamide; Pac = paclitaxel; Doc = docetaxel; TAC = docetaxel,
doxorubicin, cyclophosphamide; FAC = 5-fluorouracil, doxorubicin, cyclophosphamide
|
|
EC/Pac
|
mean age: 42
|
n = 80
|
46.6
|
Zhou, 2012
|
|
EC/Doc
|
< 35
|
n = 166
|
15
|
Fornier, 2005
|
|
TAC
|
premenopausal
|
n = 109
|
57.7
|
Martin, 2005
|
|
FAC
|
premenopausal
|
n = 409
|
52
|
Martin, 2005
|
Premature Ovarian Failure
The effect of cytotoxic therapy on ovaries is explained, amongst other things, by
the disturbance of steroid-producing granulosa cells and theca cells, resulting in
destruction of the oocytes they enclose [10]. The histological correlate is a loss of follicular structures in the ovaries associated
with fibrosis [11].
The degree of gonadotoxic effect of chemotherapy depends considerably on the substance
used and the cumulative dose. Especially anthracyclines or alkylating agents, such
as cyclophosphamide, are characterised by a high degree of cytotoxicity, as they do
not have cell cycle specificity, unlike other cytostatic agents, and, in particular,
have a cytotoxic effect particularly on non-proliferating cells [12]. Based on their gonadal toxicity risk, chemotherapeutic agents may be classified
into various risk groups ([Table 1]) [13]. In each case, the risk of persistent amenorrhoea after completion of chemotherapy
is listed. [Table 2] shows amenorrhoea rates after chemotherapy, based on the examples of selected studies
[14], [15], [16].
Cyclophosphamide is the best investigated chemotherapeutic agent and is the most discussed
in connection with gonadal toxicity: There is a four-fold higher risk of developing
premature ovarian failure as compared with other chemotherapeutic agents [17]. Furthermore, the patientʼs age plays an important role in the development and duration
of ovarian failure: older women, who already have a physiological reduction of their
primordial follicle pool, have a higher risk of developing infertility; in addition,
cyclophosphamide already produces gonadal toxicity at lower doses than would be the
case in younger women [18]. Other factors influencing chemotherapy-induced infertility include [19]:
A number of studies has dealt with establishing possible biomarkers for predicting
chemotherapy-associated amenorrhoea in breast cancer patients [20], [21], [22]. In a multicentre, randomised study involving 124 premenopausal patients, Ruddy
et al. [20] showed that anti-Mullerian hormone (AMH) levels measured before chemotherapy can
serve as a biomarker for chemotherapy-associated amenorrhoea. Twelve months after
completion of chemotherapy, 82% of the patients had amenorrhoea, with older age being
the only significant marker (p = 0.0003). Eighteen months after chemotherapy and with
an amenorrhoea rate still at 81%, both older age (OR 1.18, 95% CI 1.04 – 1.34, p = 0.008)
and lower pre-chemotherapy AMH levels (OR 0.41, 95% CI 0.18 – 0.95, p = 0.04) were
statistically significant predictors of amenorrhoea [20]. An increase of pre-chemotherapy AMH levels by 1 ng/ml would mean a 59% decrease
in the risk for developing 18-month amenorrhoea. An increase in age by one year would
result in an 18% higher probability of 18-month amenorrhoea [20].
Tamoxifen, given for the duration of at least five years as endocrine therapy for
hormone receptor-positive breast cancer, is not associated with impairment of ovarian
function [19]. Nevertheless, an age-related reduction of fertility must be assumed due to the
duration of application of tamoxifen with its anti-endocrine effect. Pregnancy should
be avoided during this time, if only because of the teratogenic properties of tamoxifen
[23]. At the end of anti-endocrine therapy, the majority of the patients is perimenopausal
to postmenopausal. For this reason, interruption of tamoxifen therapy may be considered
together with the patient after about a two-year administration period in order first
to fulfil the desire to have a child and then to complete tamoxifen treatment. This
innovative approach is currently the subject of scientific reviews [24], [25].
The potential loss of fertility due to chemotherapy causes devastating emotional stress
in many patients [26], commonly associated with episodes of depression, anxiety, grief, anger, relationship
break-ups, and reduced quality of life in general [27], [28]. Accordingly, particular importance is attached to preserving ovarian function during
and after chemotherapy, both with regard to fertility as well as maintaining healthy
bone and cardiovascular systems.
Fertility Preservation Options
In May 2006, the network FertiPROTEKT was founded in Heidelberg by a group of 40 university fertility physicians.
After 10 years, the network now has the status of a registered society and has grown
considerably in members. Fertility physicians and biologists of meanwhile over 100
university, as well as non-university, centres in Germany, Austria and Switzerland
have combined forces to offer on a nationwide basis fertility preserving measures
during chemotherapy and radiation therapy along the lines of uniform recommendations
[29].
Cryopreservation of unfertilised and fertilised oocytes
If there is enough time for ovarian hyperstimulation before planned chemotherapy,
mature oocytes can be harvested by transvaginal follicle aspiration. These can then
be fertilised by IVF or ICSI treatment and cryopreserved in the pronuclear (2-pronuclear)
stage. In Germany, only cryopreservation of fertilised oocytes is legally permitted,
while in other countries embryos may also be preserved.
Stimulation can be initiated at any time, irrespective of the patientʼs cycle day
(“random start”), and lasts about 14 days [30]. A stimulation protocol using an aromatase inhibitor (AI) in combination with gonadotropin
administration has proven successful [31]. This results in lowering plasma oestradiol levels while at the same time inducing
oestrogen production from androgens in the granulosa cells. Thus, both effects of
the AI may be optimally utilised. On the one hand, measurable oestradiol (E2) levels
in the blood are maximally suppressed, while on the other hand ovulation induction
is supported [32]. Oktay et al. were able to show that, in the antagonist protocol, stimulation using
FSH in combination with letrozole (third-generation AI) as compared with stimulation
in the long agonist protocol resulted in a significant reduction of E2 levels (p < 0.001),
with an unchanged number of harvested oocytes (p = 0.43) [32]. However, it must be pointed out that stimulation with letrozole is not recommended
in every case, but only for hormone receptor-positive tumours. Furthermore, the patients
must be informed about the off-label use of this stimulation protocol.
If the patient does not have a partner, then the oocytes are cryopreserved in an unfertilised
state. This procedure should fundamentally be offered to every woman – irrespective
of whether single, in a stable relationship or married – given the current high rates
of separation and divorce. It must be ensured that the respective centre has at its
disposal the appropriate possibility of cryopreservation.
With regard to cryopreservation, vitrification has particularly proven itself as an
extremely fast process of freezing the oocytes in nitrogen (flash-freezing). With
conventional methods, freezing is achieved significantly more slowly over several
hours and carries a high level of risk of the formation of ice crystals. Cryopreserved
fertilised oocytes have a high vitality of 73 to 95% after vitrification, similar
to cryopreserved embryos or sperms, with a pregnancy rate of about 25% [33], [34].
In-vitro maturation
In-vitro maturation (IVM) is a relatively new extracorporeal technique of assisted
reproductive medicine, which dispenses with controlled ovarian hyperstimulation, unlike
classic IVF/ICSI, and therefore does not result in a delayed start to planned chemotherapy.
This technique involves harvesting immature oocytes from small antral follicles via
transvaginal aspiration, if need be after a short stimulation with FSH and/or hCG.
A high antral follicle count (AFC) is important here, so this method can only be used
in a small subgroup.
This is followed by in-vitro maturation of the oocytes with subsequent fertilisation.
In-vitro maturation of the oocytes is usually conducted over a period of 24 hours.
There then follows an assessment of the stage of maturity and, if need be, fertilisation
by conventional IVF or ICSI. Although accelerated in-vitro maturation could theoretically
have negative effects, there has so far been no reports of an increase in malformation
rates [36]. Disadvantages of IVM as compared with conventional IVF or ICSI treatment include
[36]:
-
lower implantation and pregnancy rates per treatment cycle per embryo transfer,
-
higher costs per achieved pregnancy,
-
technically more difficult needle puncture with longer aspiration time,
-
increased laboratory costs due to increased work volume,
-
epigenetic and other foetal risks not entirely clarified.
In-vitro maturation is therefore still an experimental, non-standard procedure which
so far almost no laboratory is providing.
Cryopreservation of ovarian tissue
Since its first successful use in Brussels in 2004, cryopreservation of ovarian tissue
has established itself worldwide as an effective procedure [27]. Here, the first child was born after orthotopic, autologous transplantation of
previously cryopreserved ovarian tissue and after spontaneous conception [39].
During cryopreservation of ovarian tissue, about 50% of the ovarian cortex of one
ovary is resected by laparoscopy, prepared and preserved using cryoprotective agents.
Cryopreservation of ovarian tissue is particularly suitable for younger patients,
as their ovarian reserve and consequently their follicle density are very high. An
upper age limit of between 35 – 37 years is recommended because up to this age range
the majority of cases still has a sufficiently high ovarian follicle density. Before
the procedure, the hormone status is examined from a blood sample and ultrasound examination
of the uterus and the ovaries is performed.
Cryopreservation of ovarian tissue is particularly suitable when there is little time
available before starting cytotoxic therapy: Whereas about two weeks must be planned
for ovarian hyperstimulation with aspiration and cryopreservation of the oocytes,
laparoscopy may be performed a few days before starting chemotherapy. The option of
dispensing with hormonal stimulation, combined with a prompt conclusion of fertility
protection, makes this method appear promising, especially in the group of breast
cancer patients.
In the early days of establishing a method for re-transplantation of ovarian tissue,
the attempt was made at heterotopic tissue transplantation, i.e. in the region of
the forearm or in the abdominal wall [40]. Meanwhile, orthotopic re-implantation is usually preferred, i.e. in or at the residual
ovary or in a peritoneal pocket in the region of the ovarian fossa. Resumption of
endocrine function usually occurs within three to six months. Survival time of the
tissue varies between a few months and several years [41], [42].
It should be noted that, particularly with breast cancer, there is – at least theoretically
– a residual risk of re-induction of the cancer disease by persistent and, after re-implantation,
reactivated micrometastases [33]. Particularly in early stages (I, II), re-transplantation of ovarian tissue is regarded
as safe – malignant cells have been excluded both in histological as well as immune
histological examinations of cryopreserved ovarian tissue [43], [44]. In the advanced stage (IV) on the other hand, the risk of reinduction of the cancer
by ovarian metastases should at least be considered. In one patient, local recurrence
on the side of the diseased breast about one year after re-transplantation of ovarian
tissue has been reported. However, metastases were not detected in the ovary itself
[45], [46]. This innovative procedure has been able to progressively establish itself in recent
years and is meanwhile also being offered in Germany at selected centres [27].
Based on published cases and data submitted by the network FertiPROTEKT, currently over 90 births worldwide have been documented [47], [48].
With this method, the live-birth rate percentage is 28.4% per patient, with simultaneously
higher pregnancy rates [49]. Van der Ven reported a live-birth rate of 25%, with a pregnancy rate of over 30%
[50]
Drug treatment – GnRH agonists
The rationale behind suppression of germ cell proliferation is to initiate cell cycle
arrest with a limited treatment period using GnRH analogues, thus protecting the follicles
from the gonadotoxic effect of chemotherapy. This concept is based on the observation
that, with inactive gonads at a prepubertal age, fertility is less affected by chemotherapeutic
agents than in the reproductive phase of life. At the start of treatment with GnRH
agonists there is an initial release of gonadotropins (“flare-up” effect), lasting
for about one week, so GnRH analogues should be administered the first time at least
one week prior to the start of chemotherapy. Their use is on an off-label basis.
The benefit of GnRH analogues has been the subject of controversy for years. In a
Cochrane analysis [52] based on the evaluation of four randomised studies from the years 1987 to 2007,
the authors showed that patients profit from the use of GnRH analogues. Increased
menstruation (RR 1.90, 95% CI 1.30 – 2.79) and ovulation rates (RR 2.70, 95% CI 1.52 – 4.79)
were demonstrated after completion of chemotherapy [52]. A meta-analysis from 2011 [53], which included six studies until 2010, also found a protective effect from GnRH
analogues on ovarian function.
POEMS (Prevention of Early Menopause Study), an international Phase 3 study by the
Southwest Oncology Group (SWOG), examined the effect of goserelin on ovarian function
during chemotherapy involving cyclophosphamide. Between 2004 and 2011, 257 patients
were included in the study and followed-up for two years. The use of GnRH analogues
was shown to be associated with a lower rate of premature ovarian failure (p = 0.03)
in comparison with chemotherapy alone [54]. In addition, disease-free survival (DFS) and overall survival (OS) were examined,
each over a period of four years, and shown to have experienced a positive effect
from the addition of goserelin (DFS: 89 vs. 78%; OS: 92 vs. 82%, p = 0.05) [54].
Data obtained from the POEMS trial, however, should be assessed in a very critical
light, because problems involving financing and recruiting resulted in a premature
stop to the study. Furthermore, an excessively high drop-out rate also interferes
with interpretation of the results. The study is therefore regarded as too “under-powered”
for a reliable evaluation [55].
A meta-analysis from the year 2015 by Lambertini et al. [56] looked at 12 randomised studies involving a total of 1231 premenopausal breast cancer
patients. Temporary suppression of ovarian function by GnRH analogues was associated
with a lower risk of preterm ovarian failure (POF) (OR 0.36, 95% CI 0.23 – 0.57; p < 0.001)
[56].
The PROMISE-GIM6 study is a multicentre, randomised Phase 3 study from 2015 [57]. Between 2003 and 2008, 281 patients were included in the study. The premenopausal
patients were assigned to either the chemotherapy group (control group) or the chemotherapy
+ GnRH analogue (triptorelin) group. Primary endpoints were ovarian function, pregnancy
rate and disease-free survival. Menstruation rates on completion of chemotherapy were
reported to be 72.6% in the chemotherapy + triptorelin arm and 64% in the chemotherapy
group (HR 1.28, 95% CI 0.98 – 1.68; p = 0.071). Five-year DFS was reported to be 80.5
and 83.7% for the chemotherapy + triptorelin arm and the chemotherapy group, respectively
(HR 1.17, 95% CI 0.72 – 1.92 p = 0.519) [57]. In summary, the study reached the conclusion that GnRH analogues may be assumed
to protect ovarian function while not affecting prognosis.
The authors Elgindy and co-workers reached a different result in 2015. In their report
[58], ten randomised controlled studies, published between 1987 and 2015, were identified
and assessed. The data of 907 patients were included in the meta-analysis, with 468
women having been additionally treated with a GnRH agonist during chemotherapy. No
statistically significant differences were identified between those patients treated
additionally with GnRH analogues and those treated with chemotherapy alone (68.4 vs.
59.9%). The patients did not benefit from the administration of GnRH analogues with
regard to FSH levels (p = 0.27), nor anti-Mullerian hormone (p = 0.40), nor antral
follicular count (p = 0.17) [58].
In the light of the contradictory statements regarding the efficacy of GnRH analogues,
it is important to have a critical and detailed discussion with the patient [5].
[Table 3] provides an overview of the above-mentioned options of fertility preservation.
Table 3 Fertility preservation options in female patients with breast cancer [59].
|
Measure
|
Experimental vs. standard procedure
|
Ovarian stimulation (OS) required
|
Delayed start of chemotherapy
|
Surgical intervention
|
Preservation of ovarian function (OF)
|
Available in all centres
|
Comments
|
|
AFC = antral follicle count; CT = chemotherapy; GnRH analogues = gonadotropin-releasing
hormone analogues; OF = ovarian function; OS = ovarian stimulation
|
|
Cryopreservation of unfertilised oocytes
|
standard
|
yes
|
yes
|
yes
|
no
|
no
|
Duration of OS: 10 – 14 days
|
|
Cryopreservation of fertilised oocytes
|
standard
|
yes
|
yes
|
yes
|
no
|
no
|
Partner required
|
|
In-vitro maturation
|
experimental
|
no
|
no
|
yes
|
no
|
no
|
High AFC required, high costs, laborious procedure, practically no laboratory is currently
offering this procedure
|
|
Cryopreservation of ovarian tissue
|
experimental
|
no
|
no
|
yes
|
yes
|
no
|
Not to be recommended at an advanced tumour stage, risk of micrometastases, no long-term
data regarding OF
|
|
Ovarian suppression by GnRH analogues
|
experimental
|
no
|
no
|
no
|
yes
|
yes
|
Simple, favourable therapy, application before and during CT, few long-term data with
regard to resumption and preservation of OF
|
