Question

Are pregnancy and breastfeeding after breast cancer treatment possible?

Recommendation

Pregnancy and breastfeeding after breast cancer treatment does not need to be discouraged. The importance of prognosis in relation to her desire to have children should be discussed, however.

 

Pregnancy during tamoxifen use is advised against.

If pregnancy does occur during tamoxifen use, the agent should be ceased and possible risks should be discussed with the patient.

Conclusions

 

Level 3

Pregnancy after treatment for breast cancer does not appear to have an unfavourable influence on the prognosis of the disease.

 

C          Blakely, 2004; Gelber, 2001; Mueller, 2003; Upponi, 2003

 

Level 3

Breastfeeding after treatment for breast cancer does not appear to have an unfavourable influence on the prognosis of the disease.

 

C          Azim, 2009; Gelber, 2001

Literature summary

Pregnancy

Risks for the mother

Many patients and treating physicians are hesitant about the desirability of pregnancy after breast cancer treatment. As a result of high hormone levels during pregnancy, the growth of any micrometastases of a hormone-sensitive tumour may be stimulated.

A number of retrospective, largely case control studies have researched the effect of pregnancy on the (disease-free) survival in women previously treated for breast cancer [Upponi, 2003; Mueller, 2003; Blakely, 2004 Gelber, 2001]. Almost all studies show that pregnancy after breast cancer treatment does not have a negative effect on the (disease-free) survival. This conclusion remains controversial because of possible selection bias (healthy mother phenomenon) and the retrospective nature of the studies.

 

Risks for the unborn child

If pregnancy occurs within 6 months after radiotherapy, there is a theoretic chance that mutations in mature egg cells will lead to congenital abnormalities. This risk is dose-dependent and can be calculated [ICRP 2001, Valentin 2003]. The size of this risk is usually negligible in the case of irradiation. Whether chemotherapy has such an effect on mature egg cells is not known. An earlier treatment with chemotherapy, consisting of CMF or doxorubicin, does not lead to an increased chance of congenital abnormalities, but is associated with an increased chance of premature births (10-29%, HR 1.7) [Del Mastro, 2006].Reliable data on the late effect of treatment with taxane-containing chemotherapy or with trastuzumab is still lacking.

Seven cases have been described involving pregnancies that occurred during tamoxifen use. In two of these, severe congenital abnormalities developed; one was a craniofacial defect and the other involved congenital abnormalities of the urogenital tract [Cullings 1994, Tewari 1997, Koca, 2010]. In the latter case, a causal relationship between tamoxifen use during conception and the first weeks of pregnancy has certainly not been excluded [Tewari 1997]. Pregnancy should be advised against during hormonal treatment, and if pregnancy occurs during tamoxifen use, this should be ceased and the risks discussed with the patient.

 

Other considerations

The estimated prognosis of the breast cancer is a point of attention for the patient and her partner. After all, if the prognosis is poor for the expectant mother then the child runs the risk of losing his/her mother at a young age. Less relevant but also not negligible is the increased chance of other malignancies after breast cancer treatment, such as ovarian cancer, certainly in women with a family history of this disease (HR 1.21-1.64) [Prochazka, 2006; Hooning, 2006].

 

Breastfeeding

Clarity is lacking amongst physicians and patients on the desirability of breastfeeding by a women who has had a child after being treated for breast cancer. As far as the literature is concerned, breastfeeding does not seem to give an increased risk of recurrent breast cancer or worsening of the prognosis. In a series of 94 patients who had one or more children after breast cancer treatment with matched controls, it was found that further prognosis was better amongst the women who had had children than amongst the controls [Gelber, 2001]. In this cohort, the prognosis amongst the 27 women who had breastfed was better than that of the 25 women who had not done so and the 42 for whom the breastfeeding status was not known [Azim, 2009]. The authors note that these results may be biased, but conclude that breastfeeding does not have a negative influence on prognosis. The results are in line with the protective effect of (long-term) breastfeeding on the a priori chance of breast cancer. Women may be concerned that they are unable to provide enough breast milk, or that the treated breast produces breast milk that is damaging to the baby. Breast milk may contain fat soluble medication (e.g. taxanes) during or within a few weeks after chemotherapy, and breastfeeding is advised against in this period. After mastectomy there is only one breast and this can provide sufficient breast milk. After BCT, breastfeeding from the treated breast is possible in approximately 30-40% of women, and is not damaging for the nursing infant, but it may be painful [Azim, 2010; Freund, 2009].

Authorization date and validity

Last review : 13-02-2012

Last authorization : 13-02-2012

The national Breast Cancer guideline 2012 is a living guideline, in other words there is no standard term of revision. NABON continually watches at new developments and clinical problems in the areas of screening, diagnostics, treatment and aftercare, and whether this requires an update.

Initiative and authorization

Initiative : Nationaal Borstkanker Overleg Nederland

Authorized by:
  • Nederlandse Internisten Vereniging
  • Nederlandse Vereniging voor Heelkunde
  • Nederlandse Vereniging voor Psychiatrie
  • Nederlandse Vereniging voor Radiologie
  • Nederlandse Vereniging voor Radiotherapie en Oncologie

General details

Approximately 14,000 women (and 100 men) are diagnosed with invasive breast cancer each year in the Netherlands, and about 1,900 have an in situ carcinoma. A woman's risk of having breast cancer over the course of her life is 12-13%. This means that breast cancer is the most common form of cancer in women in the Netherlands. Early detection, particularly via national breast cancer screening, combined with adjuvant therapy followed by locoregional treatment, improves the prognosis in women with breast cancer

The guideline on Breast Cancer Screening and Diagnostics, published in 2000, was updated in 2007. In 2002, the first multidisciplinary National Breast Cancer Guideline was published, it was revised in 2004, 2005 and 2006. In 2008 both guidelines were combined to Breast Cancer Guideline, which 2012 revision is now effected.

Scope and target group

This guideline is written for all the members of the professional groups that have contributed to its development.

 

This guideline is a document with recommendations and instructions to support daily practice. The guideline is based on the results of scientific research and expert opinion, with the aim of establishing good medical practice. It specifies the best general care for women with (suspected) breast cancer and for those who are eligible for screening. The guideline aims to serve as a guide for the daily practice of breast cancer screening, diagnostics, treatment and aftercare. This guideline is also used in the creation of informational materials for patients, in cooperation with the KWF (Dutch Cancer Society).

Member of workgroup

A core group consisting of a radiologist, surgeon, pathologist, medical oncologist and radiation therapist began preparing for the revision of the breast cancer practice guidelines in 2009. A multidisciplinary guideline development group was formed in early 2010 to implement the revision. This group consisted of mandated representatives from all of the relevant specialisations concerned with breast cancer, plus two delegates from the BVN (Dutch Breast Cancer Society) (see list of guideline development group members). The benefits of such a multidisciplinary approach are obvious: not only does it best reflect the care, but it offers the greatest possible expertise for the guideline. In composing the development group, geographic distribution of the members, balanced representation of the various organisations and agencies concerned, and a fair distribution in academic background were taken into account as much as possible.

 

The guideline development group received procedural and administrative support from IKNL (Comprehensive Cancer Centre for the Netherlands) and support on methodology from Bureau ME-TA. Partial funding was obtained from SKMS (Quality Funds Foundation of Dutch Medical Specialists). This subsidy would not have been possible without the extensive assistance provided by the NVvR (Radiological Society of the Netherlands).

Declaration of interest

Partial funding for the guideline revision was obtained from the Society of Dutch Medical Specialists in the framework of the SKMS. IKNL sponsored some of the cost. On two occasions, as well as at the beginning and end of the process, all of the members of the guideline development group were asked to fill out a statement of potential conflicts of interest, in which they stated their relationship with the pharmaceutical industry. A list of these statements of interest can be found in the appendices.

Patient involvement

In developing this guideline, four clinical questions were formulated. These questions emerge from an inventory of clinical problems collected in the field from professionals, patients and patient representatives.

 

Also, A multidisciplinary guideline development group was formed in early 2010 to create and implement the revision. This group consisted of mandated representatives from all of the relevant specialisations concerned with breast cancer, plus two delegates from the BVN (Dutch Breast Cancer Society).

 

Method of development

Evidence based

Implementation

Feasibility has been taken into account in developing the guideline. This included attention to factors that could promote or hinder putting the advice into practice. Examples include the implementation of an analysis of problems, the multidisciplinary composition of the guideline development group, and making active use of support from the guideline development group members. Presenting the draft guideline to the field and communicating what, if anything, is being done with the responses, also promotes implementation. In this manner, a guideline has been developed that answers current questions in the field.

The guideline is distributed widely and is available in digital form on the Dutch Guideline Database. The guideline may also be brought to the attention of a wider audience in other periodicals or continuing education sessions, for example. To promote use of the guideline, we recommend that the regional tumour working groups and group practices, as well as scientific and professional organisations, repeatedly bring the guideline to the attention of their members. Any problems that may arise in using the guidelines can then be discussed and, when appropriate, submitted to the national guideline development group, as it is a "living" guideline. If desirable, parts of the guideline can be made more explicit by formulating regional additions or translation to the local situation in departmental and/or hospital protocols.

In principle, indicators are determined during development of the guideline that can be used to monitor implementation of the recommendations. Via a documentation project, these indicators can then be used to determine the extent of compliance with the guideline. The information from the documentation project becomes input for the revision of the guideline.

Methods and proces

This module has been evidence-based revised in 2008 and consensus based updated in 2012.

 

A revision of an existing guideline consists of revised and updated text. Revised text is new text based on an evidence-based review of the medical literature; updated text is the old guideline text which has been edited by the experts without performing a review of medical literature. Each section of the guideline states what type of revision has taken place. Each chapter of the guideline is structured according to a set format, given below. The purpose of this is to make the guideline transparent, so that each user can see on what literature and considerations the recommendations are based on.

 

Description of the literature

To the greatest extent possible, the answers to the fundamental questions (and therefore the recommendations in this guideline) were based on published scientific research. The articles selected were evaluated by an expert in methodology for their research quality, and graded in proportion to evidence using the following classification system:

 

Classification of research results based on level of evidence

A1

Research   on the effects of diagnostics on clinical outcomes in a prospectively   monitored, well-defined patient group, with a predefined policy based on the   test outcomes to be investigated, or decision analysis research into the   effects of diagnostics on clinical outcomes based on results of a study of   A2-level and sufficient consideration is given to the interdependency of   diagnostic tests.

A2

Research   relative to a reference test, where criteria for the test to be investigated   and for a reference test are predefined, with a good description of the test   and the clinical population to be investigated; this must involve a large   enough series of consecutive patients; predefined upper limits must be used,   and the results of the test and the "gold standard" must be   assessed independently. Interdependence is normally a feature of situations   involving multiple diagnostic tests, and their analysis must be adjusted   accordingly, for example using logistic regression.

B

Comparison   with a reference test, description of the test and population researched, but   without the other features mentioned in level A.

C

Non-comparative   trials

D

Opinions   of experts, such as guideline development group members

 

Conclusions

Based on the medical literature, one or more relevant conclusions are made for each section. The most important literature is listed according to the level of evidential strength, allowing conclusions to be drawn based on the level of
evidence. All the medical literature included in the conclusion is described in the bibliography.

 

Classification of conclusions based on literature analysis

1

Based   on 1 systematic review (A1) or at least 2 independent A2 reviews.

2

Based   on at least 2 independent B reviews

3

Based   on 1 level A2 of B research, or any level C research

4

Opinions   of experts, such as guideline development group members

 

Other considerations

Based on the conclusion(s), recommendations are made. However, there are other considerations that contribute to formulation of the recommendation besides literature evidence, such as safety, the patients' preferences, professional expertise, cost-effectiveness, organisational aspects and social consequences. The other considerations are mentioned separately. In this manner, it is clear how the guideline development group arrived at a particular recommendation.

 

Recommendations

The final wording of the recommendation is the result of the scientific conclusion, taking into account the other considerations. The purpose of following this procedure and drawing up the guidelines  in this format is to increase transparency.

 

References

An alphabetical list of literature references can be found at the end of the guideline.

 

All draft texts have been discussed by the guideline development group.

Search strategy

Searches are available upon request. Please contact the Richtlijnendatabase.