Fixation of Skin Flaps after Mastectomy Using Running or Interrupted Sutures for Combatting Seroma: A Protocol for a Randomised Controlled Trial (ANNIE)

Flap fixation is the most promising technique to reduce the incidence of seroma formation and its sequelae after mastectomy [1‒5]. The necessity for finding a definitive solution for seroma formation is highlighted by the number of patients who experience complications due to fluid accumulation, as much as 85% after conventional wound closure with drain placement [2, 6, 7]. Seroma is also associated with other complications, including infection, skin flap necrosis, and delayed wound healing [8, 9]. Other preventative measures besides flap fixation have been explored, such as the use of surgical devices (ultrasonic scalpels or bipolar cautery devices), external compression, and shoulder immobilisation. However, none of these proved to be successful [1, 2, 10, 11].

Therefore, to improve postoperative outcomes for breast cancer patients undergoing mastectomy, the question should not be if flap fixation should be performed, but rather how it should be performed. The two main techniques described in previous literature are sutures and the application of tissue glue between the skin flaps and the pectoral muscle [5, 12, 13]. The use of sutures can be further divided into running and interrupted sutures. Several (randomised) prospective trials were performed to compare these techniques to conventional wound closure [13‒16]. In a recent systematic review with network meta-analysis by our group, different flap fixation methods were compared using direct and indirect comparisons. Flap fixation using running sutures was superior to flap fixation using interrupted sutures or tissue glue with regard to preventing overall seroma formation, clinically significant seroma, and surgical site infections. However, this conclusion was based on indirect comparisons between both suturing techniques allowed by the network meta-analysis, as no direct comparisons had ever been performed. In addition, the scientific quality of these studies was generally low. In order to prove the superiority of running sutures, more evidence is needed. Therefore, this hypothesis is tested in this non-inferiority, randomised controlled trial (RCT). Running sutures and interrupted sutures will be compared directly with regard to the rate of complications in patients undergoing mastectomy.

This methods article was written in compliance with the SPIRIT guidelines [17].

This parallel, non-inferiority RCT will be performed at a large teaching hospital in the Netherlands. This breast cancer centre treats 450 new patients annually presenting with breast cancer. To allow for more statistical power, data of the RCT will be combined with data of a retrospective cohort of patients. This retrospective cohort consisted of patients who were included in the Seroma reduction and drAin fRee mAstectomy (SARA) trial [18] and who underwent interrupted skin flap suturing after mastectomy. This cohort comprised 125 patients. Depending on the results of the SARA trial, we will determine the drain policy for the ANNIE trial. Therefore, only patients with the same drain policy in the SARA trial will be included in this subsequent trial. After completion of the prospective part of this trial, we will compare the total cohort of patients with interrupted sutures (both prospective and retrospective) with the cohort of patients who received running sutures.

To be eligible to participate in this study, a subject must meet all the following criteria: female sex, 18 years or older with an indication for mastectomy. The following patients will be excluded from participation: patients undergoing breast conserving therapy, patients undergoing direct breast reconstruction, patients undergoing modified radical mastectomy, or patients who are unable to comprehend implications and extent of the study and those that are unable to sign for informed consent.

All eligible patients will be informed in the outpatient clinic after discussing treatment options and when the decision has been made to perform mastectomy. The initial information will be provided by one of the breast surgeons. Afterwards, the coordinating investigator will provide the patients with additional information and the patient information form. All patients will have 1 week to consider participation. After 1 week, the investigator will contact the patients by telephone to answer any further questions and ask for consent. Informed consent needs to be provided before surgery.

One group will receive flap fixation using running sutures. After removal of the breast tissue, the skin flaps will be sutured to the pectoral muscle using running sutures with Vicryl 3–0. Two or three rows of running sutures will be placed in the upper skin flap and one or two in the lower skin flap. The other group will receive interrupted sutures. After removal of the breast tissue, the skin flaps will be sutured to the pectoral muscle using interrupted sutures with Vicryl 3–0. This will be performed using a previously published guideline: at least 15 sutures will be placed approximately 3.7 cm apart [19]. Drain policy in both groups will depend on the final results of the SARA trial, which compares drain-free mastectomy with conventional drain placement after mastectomy.

Follow-up will last 3 months. Patients will be seen 7–10 days, 6 weeks, and 3 months postoperatively. The investigator will perform clinical assessments and discuss the numeric rating score (NRS) for cosmetic results. A surgeon will be available for any additional questions if needed. Figure 1 represents a full participant timeline. Table 1 represents the time schedule.

The primary endpoint of this study is the incidence of complications requiring interventions. Complications registered are overall seroma, clinically significant seroma, surgical site infections, and bleeding complications. Complications will be registered if an intervention is necessary, including seroma aspirations, oral or intravenous antibiotics, or surgical drainage.

CSS is defined as any seroma requiring aspirations due to pain or discomfort experienced by the patient caused by large amounts of seroma, characterised by tenderness of the skin, signs of infection (redness, swelling, pain), or signs of delayed wound healing (wound breakdown, necrosis, seroma leakage). Surgical site infection is defined as an infection within 30 days after surgery, with at least one of the following signs: purulent discharge, organisms isolated from an aseptically obtained culture, or signs of infection (pain/tenderness, swelling, redness, or heat) in combination with the wound being deliberately opened [20]. Bleeding complications consist of both haematoma requiring an intervention or postoperative bleeding requiring an intervention.

Secondary endpoints are surgical time in minutes (skin-to-skin) and the cosmetic result as judged by the patient, measured using an NRS ranging from 0 to 10, in which 0 equals very dissatisfied with the cosmetic results and 10 equals very satisfied with the results. In addition, for all patients, baseline characteristics will be collected. These will include: age, gender, BMI, medical history, anticoagulant use. All preoperative and postoperative information regarding pathology and treatment for breast cancer will be collected.

This trial will be a non-inferiority trial. H0 = interrupted sutures are inferior to running sutures. H1 = interrupted sutures is not inferior to running sutures. A sample size calculation was performed using R version 4.0.2. Currently, about 22% of patients who undergo mastectomy with interrupted sutures in our breast clinic have complications requiring an intervention. The non-inferiority limit was based on a clinically relevant difference, defined as a reduction of complications with at least 50%, thus an incidence of 11%. Sample size was calculated based on an 80% power with an alpha of 0.05. Using these details, sample size calculations show that both groups will need 176 patients.

As we have a retrospective cohort of 125 patients with interrupted sutures, an additional 51 patients are needed with interrupted sutures in the prospective cohort. For the running sutures cohort, 176 prospective patients are needed. The allocation ratio of the randomisation procedure was modified accordingly, as described in paragraph 2.5.

Randomisation will be performed using Research Manager, an online data management programme. Randomisation will take place after removal of the breast tissue and before closure in the operating room. Patients will be randomised in a 1:3 (interrupted vs. running) ratio. This will result in a total of 59 patients in the prospective interrupted suture group and 177 in the running suture group. In total, 184 patients will be included in the interrupted suture cohort and 177 in the running suture cohort, thus providing sufficient patients for 80% power. Blinding is not applicable.

Data will be collected by the coordinating investigator and registered in an online eCRF (Research Manager). Preoperatively, all baseline characteristics will be registered. Every follow-up visit will be registered accordingly, and data will be updated weekly.

All study related data will be stored confidentially. After inclusion, patients will be assigned a patient participant number. Passwords for this key document will only be known to the principal and coordinating investigators. Data enabling identification of patients will not be published. Data will be stored for the mandatory 15 years after the study has terminated.

The software programme for statistical analysis will be IBM SPSS Statistics in the latest version at the time of analysis. To prevent a loss of precision due to missing data, an intention-to-treat analysis will be performed; therefore, withdrawals and nonadherence will be analysed in the group to which they were randomised. An imputation method for missing data will be determined based on the specific characteristics.

As group allocation will not be completely determined by chance due to the addition of a retrospective cohort study, differences in baseline characteristics between the groups may occur. Therefore, multivariable analysis will be used when clinically relevant differences between groups at baseline are observed.

The primary endpoint is the percentage of patients developing complications requiring intervention(s) after flap fixation. This dichotomous outcome measure will be described as absolute numbers and percentages per group. We will use logistic regression analysis to compare groups. Results will be expressed as odds ratio and 95% confidence interval.

Surgical time (skin-to-skin) and cosmetic results (reported as an NRS) will be described as means ± standard deviation and will be compared using the independent sample t test. In case of perceived baseline imbalance, linear regression analysis will be used.

After inclusion of half of the prospective cohort (n = 118), an interim analysis will be conducted to confirm our previous assumptions used for the sample size calculation. This will focus on the number of patients with complications requiring an intervention. The results of the interim analysis will not be used to answer the final research question, solely to confirm the sample size. Sample size may be adjusted accordingly. If there are major differences between groups, the trial may be stopped for ethical reasons.

Monitoring will be performed by an external, independent organ (Clinical Trial Center Maastricht [CTCM]). The protection of the rights and wellbeing of the subjects, if the data are correct and complete and if the study is conducted in accordance with legal requirements in the Netherlands, will be monitored. Monitoring frequency will be determined after a risk assessment has been performed.

Adverse events are defined as any undesirable experience occurring to a subject during the study, whether or not considered related to the trial procedure. All adverse events reported spontaneously by the subject or observed by the investigator or his staff will be recorded.

A serious adverse event (SAE) is any untoward medical occurrence or effect that results in death, is life threatening (at the time of the event), requires hospitalisation or prolongation of existing inpatients’ hospitalisation, results in persistent or significant disability or incapacity, is a congenital anomaly or birth defect, or any other important medical event that did not result in any of the outcomes listed above due to medical or surgical intervention but could have been based upon appropriate judgement by the investigator and could be related to the surgical intervention. An elective hospital admission will not be considered as a serious adverse event (SAE).

SAEs will be reported through the web portal ToetsingOnline to the accredited Ethical Committee that approved the protocol, within 7 days of first knowledge for SAEs that result in death or are life threatening followed by a period of maximum of 8 days to complete the initial preliminary report. All other SAEs will be reported within a period of maximum 15 days after the sponsor has first knowledge of the SAEs. To ensure real-time monitoring, all doctors possibly seeing these patients in the emergency department or outpatient clinic are familiar with this trial. They will report the SAE to the study team upon diagnosis.

This study will be conducted in accordance with the Declaration of Helsinki (2013) and the Medical Research Involving Human Subjects Act (WMO). This trial was approved by the Institutional Ethics Committee (METCZ, NL84440.096.23) and preregistered at clinicaltrials.gov (NCT05941351).

Amendments are changes made to the research after a favourable opinion by the accredited METC has been given. All amendments will be notified to the METC that gave a favourable opinion.

Written informed consent will be obtained from all participants by a trained clinical researcher. As described, all data will be stored confidentially, using an assigned participant number. Subjects can leave the study at any time for any reason if they wish to do so without any consequences. The investigator can decide to withdraw a subject from the study for urgent medical reasons.

This will be the first trial directly comparing different suturing techniques for flap fixation after mastectomy in order to prevent seroma formation. Flap fixation has been the most promising solution for flap fixation over the last decades [2, 3, 7]. In order to minimise the incidence of seroma formation and its sequelae, optimisation of the flap fixation technique is key. Tissue glue as a fixation technique has proven to be inferior; therefore, flap fixation using sutures should be performed [2, 15, 21]. However, multiple larger flap fixation studies use different suturing techniques, which as of yet, have not been compared directly [13, 22]. A recent systematic review compared the different techniques using indirect comparisons, in which running sutures seem to be superior. However, the included studies had a low level of evidence and suturing techniques varied widely regarding location and number of sutures. The latter proved to be important in order to prevent seroma formation [19]. Therefore, this RCT will provide definite insight in the difference between both suturing techniques to improve seroma related complications arising from mastectomy.

This study is in accordance with the ethical standard of the Institutional Research Committee and with the 1964 Helsinki Declaration and its later amendments. This trial was approved by the Institutional Ethics Committee (METCZ, NL84440.096.23) and preregistered at clinicaltrials.gov (NCT05941351). Written informed consent will be obtained from all prospective cohort patients.

The authors have no conflicts of interest to declare.

No funding was received for this trial.

Merel Spiekerman van Weezelenburg, Loeki Aldenhoven, and James van Bastelaar are responsible for conceptualising, designing, and coordinating the study. Data acquisition will be performed by Merel Spiekerman van Weezelenburg, Loeki Aldenhoven, Elisabeth van Haaren, Alfred Janssen, Yvonne Vissers, and James van Bastelaar. Data analysis and statistical outline will be performed by Merel Spiekerman van Weezelenburg, Loeki Aldenhoven, and Sander van Kuijk. Study supervision was provided by James van Bastelaar and Geerard Beets. Manuscript preparation, editing, and review were performed by all authors.

The data that support the findings of this study will be available from the corresponding author upon reasonable request. Data are not publicly available due to participants’ privacy regulations.