Effects of Negative Pressure Wound Bandaging After Mastectomy

Is negative pressure wound therapy associated with a decreased risk of postoperative seroma in breast cancer patients who have undergone mastectomy?

Introduction Breast cancer is the most common cancer in women in Sweden as well as globally. In 2022, there were 2,3 million women diagnosed with breast cancer and 670 000 deaths globally. More than every tenth woman in Sweden will suffer from breast cancer during their lifetime. Since the 1970s the 10 year survival rate in Sweden has increased from around 54% to 88% and the 5 year survival rate has increased from around 69% to 93%.

There are two main types of surgical treatment for breast cancer, breast-conserving surgery and mastectomy. The number of mastectomies have gradually decreased because of decreased tumor size at diagnosis and an increased use of oncoplastic surgery and preoperative treatment. However, it still has an important role with indications like: inflammatory tumor, T4-tumor after preoperative treatment, large tumors that progress during preoperative treatment, local recurrence after previous partial mastectomy with radiotherapy, multicentric tumors, persisting positive margins after extended excision after partial mastectomy or contraindications for postoperative radiotherapy.

Wound complications after mastectomy such as surgical site infections (SSI), seromas, wound dehiscence, wound necrosis and hematoma are a frequently occurring problem. The complications are a major cause of morbidity for patients and a significant cost burden for healthcare providers. Surgical site complications in breast cancer patients can also delay the initiation of adjuvant treatment and may negatively impact both recurrence risk and overall survival.

There is research showing that Negative Pressure Wound Therapy (NPWT) reduces the risk for SSI with up to 33% compared to standard care, over a range of surgical specialties. It is also a promising technique for preventing and managing wound complications in high-risk closed incisions. NPWT is thought to reduce bacterial contamination, exudate and edema, promote lymphatic and local blood flow, and stimulate tissue granulation. No significant difference has been observed between -80mmHg and -125mmHg devices.

A systematic review and meta-analysis has shown that prophylactic application of NPWT is associated with significantly fewer surgical site complications including SSI, seroma, wound dehiscence and wound necrosis for closed breast incisions in breast surgery, compared with conventional non-NPWT dressings, while there was no significant difference in rates of hematoma. A meta-analysis showed similar results, however, with no significant difference in rates of seroma.

A range of studies looking at NPWT in various types of oncoplastic and reconstructive breast surgeries suggest an association with reduced postoperative wound complications. Some key findings are reduced mastectomy flap necrosis in skin-sparing and nipple-sparing mastectomy, improvement in quality of scarring in bilateral reduction mammoplasty, reduced development of major seroma, as well as reduced duration and total volume of seroma in prepectoral breast reconstruction. The cost-effectiveness of NPWT for reducing complications after breast surgery, especially in high-risk patients, has also been implied.

Looking at mastectomies specifically, a study evaluated postoperative wound complications following the use of NPWT in patients undergoing mastectomy. They suggested that it neither leads to fewer postoperative wound complications, nor leads to fewer patients requiring unplanned visits or fewer patients with clinically significant seroma. However, another study compared NPWT to conventional dressings in modified radical mastectomy (mastectomy + axillary lymph nodes) in high-risk patients and suggested that NPWT significantly reduced postoperative seroma, flap ischemia and flap dehiscence. No difference was determined regarding postoperative hematoma, flap necrosis and SSI.

Knowledge gap To summarize, there is limited research with contradictory results on whether NPWT decreases the risk of postoperative seroma and surgical site complications in patients who have undergone mastectomy.

Aim The aim of the study is to assess if PICO NPWT affects the risk of postoperative seroma in breast cancer patients who have undergone mastectomy compared to conventional dressings.

Hypothesis The investigators hypothesize that PICO NPWT reduces the risk of postoperative seroma in breast cancer patients who have undergone mastectomy.

Material and methods Setting Data regarding patient characteristics and postoperative complications will be extracted from patient records.

Study size The investigators will have a sample size of 76 patients based on power calculations (38 patients in the control group and 38 patients in the intervention group). Power calculations were based on 50% anticipated incidence of seroma in the control group, 10% anticipated incidence of seroma in the intervention group, a power of 90%, a P-value of 0.05 (alpha) and compensation of 20% loss to follow-up.

PICO NPWT PICO NPWT by Smith and Nephew will be used. The dressing size is 15 x 30cm. It will be applied directly on the skin in the operating theater. It is attached to a small device which is turned on continuously for 7 days and can be carried around in a pocket. It may only be paused for showers. Active drainage needs to be placed outside the dressing. If the patient has a pacemaker the device needs to be placed 10 cm apart. Contraindications for the PICO NPWT include oversensitivity to silicone and active bleeding.

Source and method of participant selection All patients with a newly diagnosed breast cancer come to the specialized surgical outpatient clinic for a primary visit to discuss their diagnosis and surgical treatment plan. They meet a breast surgeon and a contact nurse. All cases are discussed at a multidisciplinary conference. All breast cancer patients who are planned for a mastectomy will be offered to participate in the study. The type of wound dressing will be randomized during each surgery, after the surgery is finished and before wound dressings are applied. Baseline data will be recorded before randomization.

Type of data The outcomes will be measured by follow-up appointments at the outpatient clinic.

Standard care today includes the following visits to the outpatient clinic:

• Follow up after 1 day with a contact nurse to remove active drainage.
• Follow up after 2-3 weeks with a surgeon to receive the pathology report and continued treatment plan decided at the multidisciplinary conference.

The extra visits related to this study will be:

• Follow up after 7 days with a contact nurse for the intervention group to remove the PICO negative pressure wound therapy.
• Follow up after 6 months with a contact nurse for both groups (control group and intervention group).

Exposure PICO negative pressure wound therapy or conventional dressings.

Covariates High-risk groups include: BMI >30, smoking, diabetes, corticosteroids, anticoagulants, neoadjuvant chemotherapy, previous radiotherapy and immunosuppressive therapy. Age, sentinel node biopsy, axillary lymph node dissection and ASA classification will be noted.

Statistical methods and analyses The Statistical Programme SPSS will be used and the statistical analyses will be conducted by an external statistician from CKF Dalarna.

Funding Funding through surgical residency project.