Use of the Da Vinci SP ® Surgical System in Robot-assisted Nipple-sparing Mastectomy: A Single-Center, Retrospective Study

doi:10.21203/rs.3.rs-4868747/v1

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Use of the Da Vinci SP ® Surgical System in Robot-assisted Nipple-sparing Mastectomy: A Single-Center, Retrospective Study

https://doi.org/10.21203/rs.3.rs-4868747/v1

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We investigated the safety and performance of the Da Vinci SP single-port robot (SP robot) in nipple-sparing mastectomy (NSM) with immediate reconstruction. Medical records of 60 women aged ≥ 19 years who had undergone SP robot-assisted unilateral or bilateral NSM with immediate reconstruction between October 2020 and August 2021 were retrospectively analyzed. Stage I (31, 47.1%) was the most common pathological tumor-node-metastasis stage, followed by stages II (22, 33.3%), 0 (7, 10.6%), and III (4, 6.0%). The median total duration of NSM performed by a breast surgeon and reconstruction performed by a plastic surgeon was 154.0 min (interquartile range [IQR], 130.5–206.0 min) and 133.0 min (IQR, 80.0–255.0 min), respectively. The median length of hospitalization was 5.5 d (IQR, 3.0–9.0 d). Conversion to robotic multiport or open surgery was not required in any case. The median duration to drain removal was 5.0 d (IQR, 4.0–6.0 d). Recurrence of cancer within 6 months was not observed in any patient. SP robot-assisted NSM with immediate reconstruction was performed successfully in all patients without conversion to open surgery or the incidence of significant perioperative complications, indicating its precision and ability to minimize the size of the surgical incision.

Biological sciences/Cancer

Health sciences/Diseases

Health sciences/Oncology

breast cancer

Da Vinci SP

immediate reconstruction

nipple sparing mastectomy

reconstruction

robot-assisted surgery

The increase in the early detection of breast cancer has led to an increase in the proportion of patients undergoing breast-conserving surgery (BCS); nevertheless, 30% of patients continue to undergo mastectomy.[1, 2] The number of patients undergoing nipple-sparing mastectomy (NSM) and reconstruction has been gradually increasing as this approach facilitates the maintenance of the shape of the breast and yields a prognosis similar to that offered by conventional mastectomy.[3, 4] However, compared with mastectomy and BCS, NSM is a relatively difficult surgical technique as it involves a large surgical field. Furthermore, caution must be exercised while reflecting the flap. Reflection of a thin flap can lead to necrosis of the skin, whereas reflection of an excessively thick flap increases the risk of local recurrence. Thus, the reflection of a flap of an appropriate thickness is important.[5] The incision made on the skin must be lengthened to secure a sufficient surgical field and facilitate the smooth operation of the surgical instruments; however, this leads to a reduction in cosmetic satisfaction and the incidence of skin necrosis owing to poor blood supply to the flap.[6] Therefore, endoscopic NSM (ENSM) was introduced to improve oncological safety and cosmetic satisfaction.[7, 8] However, the approach of cameras and instruments from various angles in a narrow space hampers the completion of ENSM, which requires performing various movements. Consequently, this approach is not used widely.[9]

Robot-assisted surgery is performed using multi-joint endoscopes and instruments, which facilitate precise surgery via the creation of small incisions. Robotic surgery has been performed widely in the domains of colorectal surgery, prostatectomy, hysterectomy, cystectomy, and gastric surgery. The first robot-assisted breast surgery was reported in 2017.[10–14] Recent studies have demonstrated that the safety profile of robotic NSM (RNSM) is similar to that of conventional NSM. Furthermore, the oncological outcomes of RNSM are comparable with those of NSM.[15–18] A recent systematic review and meta-analysis revealed no statistically significant differences between traditional NSM and RNSM in terms of the incidence of postoperative complications, including implant loss, hematoma, (flap) necrosis, infection, and seromas [18].

The Da Vinci SP system (Intuitive) for SP procedures is equipped with articulating robotic cameras and three 6-mm, double-jointed, articulated instruments that can be used in various surgical fields [19]. Most NSMs are performed using a single incision; thus, the utility of the Da Vinci SP system, although expected to be high, remains unknown.

We aimed to evaluate the safety and performance of the Da Vinci SP surgical system, instruments, and accessories in NSM with immediate reconstruction.

Table 1 presents the preoperative general characteristics of the patients. The median age and body mass index (BMI) of the patients were 47.0 years (interquartilerange [IQR], 41.0–51.5 years) and 22.8 kg/m² (IQR, 21.3–24.5 kg/m²), respectively. The most common cup size, determined based on the size of the bra that the patient usually wears, was moderate (23 patients, 34.8%), followed by small (16, 24.2%) and small-to-moderate (10, 15.2%). Forty-four (73.3%) of the 60 patients were premenopausal. All patients had been diagnosed with breast cancer, and none had undergone prophylactic surgery. Six patients had bilateral breast cancer. Eleven patients (18.3%) had a family history of breast cancer.

The location of the surgical incision was mid- or anterior-axillary in all 60 patients (100%) (Fig. 1). The median number of drainage tubes per patient was 3.1 (IQR, 2.0–6.0), and gas was used during surgery for 57 patients (86.2%). All 60 (100%) patients, including the six patients with bilateral breast cancer, underwent sentinel node biopsy (SNB). Notably, only 12 (18.2%) patients underwent axillary lymph node dissection (Table 2). Patients with positive SNB results underwent axillary lymph node dissection.

The median duration of RNSM and reconstructive (plastic) surgery was 154.0 min (IQR, 130.5–206.0 min) and 133.0 min (IQR, 80.0–255.0 min), respectively. The duration of plastic surgery included the placement of the implants and autologous reconstructive surgery. The median duration of using the robotic system was 30.0 min (IQR, 20.0–40.0 min) (Table 3).

One (1.7%) patient with hypotension was transferred to the intensive care unit (ICU) postoperatively. A temporary drop in blood pressure was observed in this patient owing to intraoperative bleeding. The patient was transferred to the ICU for 1 d after surgery and transferred to a general ward subsequently. Three (5%) patients underwent reoperation within 1 month of surgery to remove a hematoma that developed at the surgical site postoperatively (n=2) and wound debridement (n=1) under general anesthesia in the operating room. The median length of hospitalization was 5.5 d (IQR, 3.0–9.0 d). The median length of hospitalization for patients who underwent direct-to-implant (DTI) and deep inferior epigastric perforator surgeries was 5 d and 7 d, respectively. The median duration from the date of the surgery to the removal of the drainage tube was 5.0 d (IQR, 4.0–6.0 d) (Table 4). This duration refers to the interval until the removal of the first drainage tubes inserted after surgery. Invasive ductal carcinoma was the most common type of cancer in this cohort, and it was detected in 54 (81.8%) patients. Seven (10.7%) patients had ductal carcinoma in situ, whereas two (3.0%) patients had invasive lobular carcinoma. Fifty-nine (89.4%), 44 (66.7%), and 48 (72.7%) tumors exhibited estrogen receptor (ER)-positivity, progesterone receptor (PR)-positivity, and human epidermal growth factor receptor 2 (HER2)-negativity, respectively. The median Ki-67 value was 20% (IQR, 5–35%). All tumors underwent intraoperative subareolar resection-margin frozen biopsy. Frozen biopsy did not reveal nipple-areolar complex (NAC) involvement in any of the cases; however, permanent biopsy revealed NAC involvement in one case (1.5%). This patient underwent nipple resection. Permanent biopsy revealed a positive superficial margin in one (1.5%) patient. This patient received additional radiotherapy in addition to adjuvant treatment after surgery. The pathological staging of the tumors was as follows: T1 stage, 35 (53.0%) tumors; T2 stage, 17 (25.8%) tumors; and T3 stage, 5 (7.6%) tumors. The N stage was N0 and N1 in 50 (75.8%) and 11 (16.7%) tumors, respectively. Distant metastasis was not observed in any of the cases (M0 stage in all cases; 100%). Stage I (31; 50.0%) was the most common pathological tumor-node-metastasis stage, followed by stage II (22, 33.3%) and stage 0 (7, 10.1%) (Table 5).

Nineteen (31.7%) patients received adjuvant therapy after surgery. Among them, nine (15.0%) patients received chemotherapy only, whereas three (11.7%) patients received radiotherapy only. Seven (11.7%) patients received chemotherapy and radiotherapy. Recurrence of cancer was not observed in any patient during the 6-month follow-up period (Table 6).

No intraoperative adverse events (AEs) were observed; however, postoperative AEs were observed in 12 patients within 1 month of undergoing surgery. Five patients developed NAC necrosis, whereas six patients developed hematomas. Five patients experienced Grade III AEs requiring surgical correction under general anesthesia (Table 7). The AEs were followed up over a 6-month period in three patients. Fluid collection (n=1), cellulitis (n=1), and NAC deformity (n=1) were observed during this period (Table 7).

Multivariate analysis performed to identify the characteristics associated with complications revealed that RA-NSM, higher BMI, higher breast weight, and shorter distance from the nipple showed statistically significant associations with the incidence of skin flap necrosis (p <0.001, 0.040, and <0.001, respectively). Higher BMI and shorter distance from the nipple showed statistically significant associations with the incidence of NAC necrosis (p <0.001 and <0.001, respectively) (Supplementary Table 1).

An increasing number of patients with breast cancer are undergoing BCS; however, some patients continue to undergo total mastectomy [20]. The number of patients undergoing reconstructive surgery for cosmetic purposes is also increasing, accompanied by an increase in the demand for cosmetic results and patient satisfaction with total mastectomy [21]. A deviation from this trend was observed in the domain of breast surgery, which aims to focus on the therapeutic aspects and improve the physical and emotional well-being of patients [22]. Therefore, we evaluated the safety and feasibility of performing Da Vinci SP robot-assisted surgery as an alternative to breast reconstruction surgery by examining the duration of surgery, complication rates, and other related factors.

The present study demonstrated that the safety profile of robot-assisted breast surgery was similar to that of conventional NSM reported in previous studies. The complication rates and oncological outcomes of robot-assisted surgery and conventional surgery are identical, indicating the potential benefit of using the Da Vinci SP system in breast surgery. AE occurred in 18.2% of the 60 patients who underwent RNSM with the Da Vinci SP system. Among these patients, 7.6% received interventions beyond conservative treatment owing to the severity of AEs, and 3.0% required surgical intervention. All patients recovered completely. The findings of the present study are consistent with those of previous studies related to RNSM. The incidence of hematoma, NAC necrosis, skin necrosis, and infection was reported in 1.2–4.3%, 0–1.9%, 2.5–4.3%, and 1.2–2% patients, respectively. Moreover, only 7.6% of patients experienced AEs of Clavien–Dindo grade III or higher, which required surgical intervention. This prevalence was lower than that reported by a previous multi-center study (11.6%) [23].

Robot-assisted surgery requires smaller incisions than conventional surgery. This reduces the incidence of complications, such as bleeding and infection, in addition to reducing the pain and hospitalization period [24]. Furthermore, the surgical area can be expanded three-dimensionally to facilitate a detailed view. Consequently, robotic assistance has been used in various types of surgeries to reduce surgeons’ fatigue.

Conversion to robotic multiport or open surgery was not required in any of the cases in this study. Twenty-five AEs were observed within 1 month of surgery; however, all patients recovered without experiencing major complications. Similarly, all patients who experienced AEs within 6 months of surgery recovered without experiencing complications. Additional analysis with a larger number of patients is warranted in the future as the number of patients included in the present study was small. The learning curve of RNSM was not analyzed separately; however, an experienced surgeon who has already performed conventional NSM can perform robot-assisted total mastectomy without difficulty after the first few surgeries. The findings of the present study suggest that Da Vinci SP robot-assisted NSM is a reliable and effective treatment option for patients with breast cancer.

RNSM is performed using a single incision in most cases; thus, the utility of the Da Vinci SP system is expected to be high. Additional advanced surgical robot tools must be developed to enhance surgical precision, reduce the incidence of complications, and improve surgical outcomes. Furthermore, the shortening of the duration of surgery and hospitalization period increases patient satisfaction and facilitates the efficient distribution of medical resources.

The balance between oncologic safety and cosmetic outcome remains an important point to be considered during surgical treatment. Surgeons must make choices according to the preferences and clinical needs of the patient. Thus, the findings of this study involving the Da Vinci SP RNSM and immediate reconstruction contribute to the ongoing discourse on surgical advancements in breast oncology. The integration of robotic technology and reconstructive procedures will also continue to advance as the domain of breast surgery continues to develop. Further research and technological innovations are expected to improve surgical techniques, enhance patient experience, and advance the treatment of patients with breast cancer.

The duration of traditional NSM and RNSM was not compared in the present study; however, a previous study conducted at our hospital reported that the duration of implant and autologous NSM was 183.0 ± 46.5 (implant) and 445 ± 122.9 min (autologous), respectively. This finding indicates no difference between traditional NSM and RNSM in terms of the duration of surgery [25].

Despite the promising outcomes reported herein, the present study has some limitations. The retrospective nature of the study and relatively small sample size warrants caution while generalizing the results to broader populations, as data collected in a retrospective study may not facilitate a completely accurate statistical analysis. Furthermore, all minor side effects that occurred after surgery were included as the medical records were retrospectively analyzed in the present study. This may explain the relatively higher rate of side effects observed in the present study. As with any new surgical technique, a learning curve may impact outcomes. Thus, long-term follow-up is necessary to evaluate the oncologic and cosmetic outcomes. Nevertheless, the present study is novel in that it presents the initial data from a single center regarding mastectomy and reconstructive surgery performed using the Da Vinci SP robot. This pioneering aspect of the study underscores its significance, as it addresses a previously unexplored avenue in the field of breast surgery.

Further larger-scale, prospective studies that encompass a more diverse patient population must be conducted in this field. Long-term follow-up assessments must be performed to achieve a more comprehensive understanding of the durability of surgical outcomes and potential long-term effects. Expanding the scope of the application of the da Vinci SP system in more complex surgical scenarios and exploring its utility in conjunction with other innovative technologies could be avenues for further research.

In conclusion, this single-center, retrospective study revealed that patients with breast cancer underwent Da Vinci SP-assisted RNSM successfully without conversion to open surgery or the incidence of significant perioperative complications. Thus, this surgical system can be utilized in patients undergoing NSM who require precise breast surgery while minimizing the size of the surgical incision.

Patients

The medical records of patients who underwent Da Vinci SP robotic-assisted NSM with immediate reconstruction performed by experienced breast surgeons between October 2020 and August 2021 were retrospectively analyzed. Only cases performed by breast surgeons with > 10 years of experience performing conventional NSMs who had previously performed > 10–20 NSMs using the Xi Robot system were eligible for inclusion in this study. Deidentified data were collected and analyzed retrospectively. Sixty women aged ≥ 19 years at the time of surgery who had undergone SP robotic-assisted unilateral or bilateral NSM with immediate reconstruction using the Da Vinci SP system were included in this study. The patients elected to undergo robotic surgery following an in-depth consultation with the surgeon. All patients except for those with direct invasion of breast cancer into the nipple or skin were eligible to undergo robotic surgery. Patients who were not eligible to undergo NSM and those who were not eligible to undergo breast reconstruction (e.g., patients whose tumors had invaded the skin and nipples) were excluded from this study. Four investigators with experience in performing minimally invasive surgery and robotic surgery participated in this study conducted at the Asan Medical Center, Republic of Korea. ER- or PR-positivity was defined as nuclear staining of ≥ 1% or an Allred score of 3–8, based on the results of immunohistochemical (IHC) staining. HER2-positivity was defined as 3 + on IHC staining or HER2 amplification indicated by the presence of fluorescence in in situ hybridization. Pathological staging was performed in accordance with the seventh edition of the American Joint Committee on Cancer Staging Manual.

The study protocol was reviewed and approved by the Institutional Review Board (IRB) of Asan Medical Center (IRB 2022-0078). The requirement for obtaining informed consent from the patients was waived by the IRB owing to the retrospective nature of this study.

Surgical Methods

The surgeon seated at the surgeon console controlled all movement of the EndoWrist SP instruments and camera instrument during the procedure using two master controls and a set of foot pedals. The patient cart with four independent instrument drives on a single arm was positioned at the operating room table. A camera instrument attached to one instrument drive provided a high-resolution, three-dimensional view of the surgical site. A suite of EndoWrist SP instruments could be attached to and detached from the remaining three instrument drives to perform various surgical tasks. The camera instrument and up to three surgical instruments, which entered through a single cannula, could be used simultaneously. The EndoWrist SP instruments have a unique articulating design at the distal tip that mimics the human wrist and elbow to facilitate triangulation and independent planar movement of each instrument as all instruments enter the body through an SP.

The patient was made to assume the supine position with their arm abducted at 90–100º and placed on the arm board or bent and placed above the head (Fig. 1). Mastectomy was commenced with sharp dissection or electrocautery with an incision 4–5 cm in length (Fig. 2). The decision to use gas during surgery was made at the discretion of the surgeon. The superficial layer and posterior breast spaces were dissected manually to the maximum extent within the range of easy robotic manipulation after SNB. Axillary surgery, if necessary, was performed through the total mastectomy incision. An Alexis O wound protector or UNI-PORT wound retractor was prepared, and the cannula of the robotic system was inserted into the GelPoint (Applied Medical, Rancho Santa Margarita, CA, USA) or UNI-PORT attached to the wound protector by the surgeon. This protector was not used in patients who were not exposed to gas. The patient cart was moved to the opposite side of the surgical field by the surgeon, and an additional 5-mm port was inserted into the GelPoint or UNI-PORT beside the cannula of the robotic system. A camera was installed in the camera port, and Da Vinci SP fenestrated bipolar forceps, Da Vinci SP Maryland bipolar forceps or Cadiere forceps, and Da Vinci SP monopolar curved scissors were mounted on arms 1, 2, and 3, respectively. The robot was undocked to obtain a specimen after the breast parenchyma was separated completely. The protector inserted to use the robotic device was not removed by the surgeon when obtaining the specimen. A suture was made in the 3 o'clock or 9 o'clock direction by the surgeon to indicate the direction before obtaining the specimen.

Statistical Methods

All clinical data and the incidence rates of surgical complications were collected retrospectively by reviewing the medical records of the patients. All patients were included in the analysis, regardless of the completeness of their data. The preoperative, intraoperative, and postoperative characteristics were analyzed. Continuous variables are presented as the median and IQR (e.g., age and duration of surgery). Discrete variables are presented as a proportion of the total (e.g., sex and conversion). All statistical analyses were performed using SPSS version 21.0 (IBM Corp., Armonk, NJ, USA).

Acknowledgments

This study was supported by a grant (2022-0078).

Author contributions

All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Sae Byul Lee, Jisun Kim, Il Yong Chung, Hee Jeong Kim, Jong Won Lee, Byung Ho Son, and Beom Seok Ko. The first draft of the manuscript was written by Sae Byul Lee, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. We further confirm that the order of authors listed in the manuscript has been approved by all authors.

Data availability statement (mandatory)

The datasets analyzed during the current study are not publicly available as the personal information of patients must be protected, but are available from the corresponding author on reasonable request.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was waived because the study was based on retrospective clinical data.

Conflicts of interest

The authors declare no conflict of interest.

Funding

This study was conducted with funding from Intuitive Surgical, Inc.

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Table 1. Preoperative general characteristics

Variable		N = 60
Age, median (IQR, year)		47.0 (41.0–51.5)
Sex	Female	60 (100%)
BMI, median (IQR, kg/m²)		22.8 (21.3–24.5)
Breast ptosis grade*	No ptosis Grade I Grade II Grade III Glandular ptosis Unknown	14 (21.2%) 8 (12.1%) 4 (6.1%) 1 (1.5%) 1 (1.5%) 38 (57.6%)
Cup size*	Small Small-to-moderate Moderate Moderate-to-large Large Huge Unknown	16 (24.2%) 10 (15.2%) 23 (34.8%) 6 (9.1%) 6 (9.1%) 1 (1.5%) 4 (6.1%)
Germline mutation status	Mutated Wild-type Unknown	2 (3.3%) 20 (33.4%) 38 (63.3%)
Menopause status	Premenopausal Postmenopausal Perimenopausal	44 (73.3%) 15 (25.0%) 1 (1.7%)
Tobacco smoking	Never smoked Current smoker	56 (93.3%) 4 (6.7%)
Preoperative Hb, median (IQR, g/dL)		12.8 (12.0–13.4)
Comorbidity	History of cancer History of hypertension Connective tissue disease Diabetes Liver disease Renal disease	3 (5%) 4 (6.7%) 1 (1.7%) 4 (6.7%) 4 (6.7%) 1 (1.7%)
Preoperative diagnosis*	IDC ILC DCIS LCIS Mucinous carcinoma	35 (53.3%) 4 (6.1%) 25 (37.9%) 1 (1.5%) 1 (1.5%)
Family history of breast cancer	No Yes (first-degree relatives) Yes (second-degree relatives)	49 (81.7%) 7 (11.7%) 4 (6.7%)
Multiplicity	Single lesion Multifocal lesions Multicentric lesions	40 (60.1%) 24 (36.4%) 2 (3.0%)
Location of the breast cancer lesion	Bilateral Unilateral: left Unilateral: right	6 (10%) 30 (50%) 24 (40%)
Clinical stage^a
cT stage	T1 T2 T3 T4 Unknown	1 (1.5%) 5 (7.6%) 1 (1.5%) 1 (1.5%) 56 (84.9%)
cN stage	N0 N1 N2 Unknown	5 (7.6%) 2 (3.0%) 1 (1.5%) 56 (84.9%)
cM stage	M0 M1	66 (100%) 0 (0%)
cTNM stage	0 I II III Unknown	0 (0%) 1 (1.5%) 6 (9.1%) 1 (1.5%) 56 (84.9%)
Neoadjuvant chemotherapy		8 (12.1%)

^aSurgery on each side is considered a separate case in cases involving bilateral breast surgery (total N = 66 procedures). Clinical stage was applied only to patients who underwent neoadjuvant chemotherapy.

BMI, body mass index; Hb, hemoglobin; IQR, interquartile range; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; DCIS, ductal carcinoma in situ; LCIS, lobular carcinoma in situ

Table 2. Intraoperative characteristics

Variables		N = 60
Location of the incision^a	Mid or anterior axillary	66 (100%)
Immediate breast reconstruction*	One stage Two stage Implant DIEP LD flap	65 (98.5%) 1 (1.5%) 38 (57.6%) 26 (39.4%) 2 (3.0%)
Drainage number (average, IQR)		3.1 (2.0–6.0)
Using gas^a	Yes No	57 (86.2%) 9 (13.8%)
Sentinel node biopsy*		66 (100%)
Axillary lymph node dissection*		12 (18.2%)

^aSurgery on each side is considered a separate case in cases involving bilateral breast surgery(total N = 66 cases).

DIEP, deep inferior epigastric perforator; LD, latissimus dorsi; IQR, interquartile range

Table 3. Intraoperative details: surgical outcomes

Variables		N = 60
Duration of surgery: NSM performed by breast surgeon, median (IQR, min)	Duration of unilateral surgery, median (IQR, min) Duration of bilateral surgery, median (IQR, min) Robotic procedure time, median (IQR, min)	154.0 (130.5–206.0) 150.5 (122.8–181.0) 209.0 (198.0–238.0) 30.0 (20.0–40.0)
Duration of surgery: reconstruction performed by plastic surgeon, median (IQR, min)	Duration of unilateral surgery, median (IQR, min) Duration of bilateral surgery, median (IQR, min)	133.0 (80.0–255.0) 113.0 (77.0–231.0) 301.5 (243.5–376.8)
Estimated blood loss, median (mL)^a		<10
Intraoperative transfusion		0 (0%)
Conversion to alternative methods		0 (0%)
Intraoperative adverse events		0 (0%)

^aValue represents an estimate as measuring the insignificant amount of blood loss was challenging. Blood loss at the time of reconstruction surgery is not included. Only blood loss during nipple areola skin-sparing mastectomy surgery was measured.

Table 4. Postoperative details: Surgical outcomes

Variables	N = 60
Number of patients admitted to ICU	1 (1.7%)
Days to drain removal, median (IQR, postoperative day)	5.0 (4.0–6.0)
Duration (days) of postoperative hospital stay, median (IQR, postoperative day)	5.5 (3.0–9.0)
Unplanned procedure-related reoperations within 1-month postoperative^a	3 (5.0%)
Unplanned procedure-related readmissions within 1-month postoperative	0 (0%)

^aThree patients underwent reoperation for wound debridement (n=1) and the management of bleeding (n=2).

ICU, intensive care unit; IQR, interquartile range

Table 5. Pathological data

Variables		N = 66 procedures
Tumor size, median (IQR, mm)^a		10 (1–27)
Histology^a	DCIS IDC ILC Others	7 (10.7%) 54 (81.8%) 2 (3.0%) 3 (4.5%)
Total number of lymph nodes harvested, median (IQR, mm)^a		4 (2-8)
Total number of positive nodes, median (IQR, number)^a		0.76 (0–26)
ER	Negative Positive	7 (10.6%) 59 (89.4%)
PR	Negative Positive	22 (33.3%) 44 (66.7%)
HER2^b	0 1+ 2+ 3+	14 (21.2%) 16 (24.2%) 19 (28.8%) 17 (25.1%)
SISH	Amplified Non-amplified	1 (5.3%) 18 (94.7%)
Ki-67, median (IQR, %)		20 (5-35%)
Frozen biopsy performed		65 (98.5%)
Positive superficial margin^c		1 (1.5%)
NAC involvement (frozen)		0 (0%)
NAC involvement (permanent)		1 (1.5%)
Pathological stage^a
T stage	T0 T1 T2 T3 T4 Tis	3 (4.5%) 35 (53.0%) 17 (25.8%) 5 (7.6%) 0 (0%) 6 (9.1%)
N stage	N0 N1 N1mi N2 N3	50 (75.8%) 11 (16.7%) 4 (6.0%) 0 (0%) 1 (1.5%)
M stage	M0 M1	66 (100%) 0 (0%)
TNM stage	0 I II III Other (pCR)	7 (10.6%) 31 (47.1%) 22 (33.3%) 4 (6.0%) 2 (3.0%)

^aSurgery on each side is considered a separate case in cases involving bilateral breast surgery (total N = 66 cases).

^bHER2: reported as a score of 0–3. (0 or 1+: HER-negative/2+: borderline/3+: HER2-positive)

^cOne was superficial margin-positive, which was a permanent result.

IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; DCIS, ductal carcinoma in situ; NAC, nipple-areolar complex; IQR, interquartile range; pCR, pathological complete response; ER, estrogen receptor; PR, progesterone receptor

Table 6. Short-term follow-up (6 months postsurgery)

Variables		N = 60
Patient received adjuvant therapy^a	Chemotherapy only Radiotherapy only Chemotherapy and radiotherapy	19 (31.7%) 9 (15.0%) 3 (16.7%) 7 (11.7%)
Recurrence assessment		60 (100%)
Recurrence		0 (0%)

^aThe 6-month follow-up data were collected for patients who completed 6-month postoperative follow-up by the time the Institutional Review Board approved this study.

Table 7. Details of adverse events that occurred within 1- and 6-months follow-up period

Individuals with AEs			1-month f/u	6-month f/u
Individuals with AEs			N = 12	N=3
Number of AEs			12	3
Grade (Clavien–Dindo classification)	Grade I	NAC necrosis	2 2
	Grade II	Hematoma NAC necrosis Cellulitis Fluid collection	5 4 1	2 1 1
	Grade IIIa	NAC necrosis Pneumothorax	3 2 1
	Grade IIIb	Hematoma NAC deformity	2 2	1 1
AE type	NAC necrosis	Grade IIIa Grade II Grade I	5 2 1 2
	Hematoma	Grade IIIb Grade II	6 2 4
	Cellulitis Fluid collection NAC deformity	Grade II Grade II Grade IIIb		1 1 1
	Pneumothorax	Grade IIIa	1

AEs, adverse events; NAC, nipple-areolar complex

No competing interests reported.

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Use of the Da Vinci SP ® Surgical System in Robot-assisted Nipple-sparing Mastectomy: A Single-Center, Retrospective Study

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