The purpose of this study is to examine different outcomes of breast reconstruction in women who are treated for breast cancer with skin sparing mastectomy and subsequently a primary implant based reconstruction by one of two different techniques with either a pre- or retropectoral placement of the implant.

The main objective of the study is to establish whether one of these techniques may result in a superior outcome and thus should be recommended as first choice treatment rather than the other.

Women diagnosed with breast cancer, large areas of ductal carcinoma in situ or a hereditary high risk of breast cancer are offered a mastectomy either as a therapeutic or a risk reducing intervention. Those, who are found eligible for an immediate breast reconstruction using an implant are reconstructed by either a skin sparing mastectomy (SSM) or a nipple sparing mastectomy (NSM) using an extracellular matrix. The current technique is to place the implant in a retropectoral pocket in which the cranial part of the implant is covered by the major pectoral muscle, whereas the caudal part of the implant is covered and supported by an extracellular dermal matrix (ADM) as a hammock.

Recent focus on the functional outcome has, however, identified a new challenge - breast animation deformity (BAD), breast distortion or "jumping breast". The consequence of the condition is that women with aesthetic pleasant results, in rest, experience breast animation deformity during contraction of the major pectoral muscle. Evaluation of forty breast augmented women with a subpectoral positioning of the implant revealed that 77.5% had some kind of distortion during movement of the arm. In these healthy individuals, however, the condition is partly hidden by the glandular tissue and subcutaneous fatty tissue.

The condition is more severe in women with a reconstructed breast using a retropectorally placed implant, where the glandular tissue has been removed, leaving only the subcutaneous fatty tissue to cover the muscle and implant. The investigators know from experience and from reviewing unpublished clinical pictures and videos of thirty patients, who had an immediate breast reconstruction using the hammock technique, that the vast majority of patients have a pronounced degree of BAD.

Patients, who have a prepectoral placement of their implant, tend to have a lesser degree of BAD. The functional outcome of the prepectoral placement of the implant has previously not been compared to the retropectoral placement of the implant in women reconstructed by an implant and an ADM. A possible disadvantage of a prepectoral placement of the implant may be less soft-tissue coverage supplied by the pectoral muscle leading to higher risk of significant capsular formation. Less soft-tissue coverage may also result in a more visible implant border and rippling. Furthermore, the implant will not benefit from the abundant vascularity of the muscle and in theory perhaps not be as resistant to infections and implant loss as the subpectoral positioned implants.

The primary aim of this study is to compare the degree of BAD following a prepectoral to a retropectoral placement of the implant using the hammock for immediate breast reconstruction. For this purpose we have designed two separate trials:

Retrospective Follow-up trial: The investigators plan to invite a total of forty patients to compare breast animation deformity and shoulder and arm morbidity in a retrospective cohort of patients. Twenty patients, who have had a conventional immediate breast reconstruction with a retropectoral placement of the implant will be compared to twenty patients , who have had an immediate breast reconstruction with a prepectoral placement of the implant.

Randomized clinical trial: Investigators plan to collect, examine and compare data on the two surgical techniques in order to test superiority of the prepectoral implant based reconstruction in accordance with our hypothesis that it leads to lesser degree of BAD and better functional outcomes.

The trial is thus designed with two parallel study-arms as participants are allocated to reconstruction by either retro- or prepectoral placement of the implant in the ratio 1:1.

As the clinically most important parameter seems to be breast animation deformity this will serve as primary end-point. Functional changes in shoulder and arm function between the two surgical techniques is also a very important perimeter to investigate and will be analysed as secondary end-points.

In addition to the above data a number of other patient related outcomes will be collected as part of this trial.

Designed as a multicentre trial, participant enrollment and data Collection will be performed at academic Hospitals in Denmark and Norway.

A password protected Electronic database placed on a secure server will be established. This database will only be accessible to the primary investigator of the research Group who will be involved in the analysis of the data.

This study will provide a better knowledge of the expected outcome of immediate breast reconstruction, when it is performed by one of these two surgical techniques. The investigators expect that these results will help determine if the prepectoral implant placement may represent a better and gentler method for reconstruction of the breast with lower morbidity than the retropectoral implant placement. In all cases the results of this trial will enable us to provide our patients with better and more objective information, before they are subjected to immediate breast reconstruction.

Inclusion Criteria:

Women over 18 years referred to the Department of plastic surgery, Odense University Hospital, Lillebaelt Hospital Vejle, Denmark or Telemark Hospital, Skien, Norway between January 2017 and July 2018, who are found eligible for immediate breast reconstruction.

Exclusion Criteria:

1. Dementia that makes it impossible to obtain informed consent
2. Non-Danish speaking patients from whom informed consent cannot be obtained by interpreter
3. Tobacco users
4. Women with known hypertension treated with more than one drug
5. Women who had pre-surgical radiation therapy.
6. Women planned to have postsurgical radiation therapy.
7. BMI above 32 or below 22

However, the final decision relies on sufficient thickness of the skin flaps after mastectomy prior to immediate reconstruction.

Invited patient will receive both oral and written participant information after which there will be as many days for reflection as the treatment guaranty for cancer allows.

Patients considering participation will be invited for a second consultation where written informed consent will be obtained from all who accept the invitation. Randomization will be performed during surgery, prior to reconstruction. Patients who do not wish to participate will be reconstruction with the implant placed retropectoral.