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The Influence Of Fat Grafting On Breast Imaging After Post-mastectomy Reconstruction: A Matched Cohort Analysis
Roger W. Cason, M.D., Ronnie L. Shammas, M.D., Gloria Broadwater, M.S., Adam D. Glener, M.D., Amanda R. Sergesketter, M.D., Rebecca Vernon, B.S., Elliot Le, B.S., Victoria A. Wickenheisser, B.S., Caitlin E. Marks, B.S., Jonah Orr, B.S., Scott T. Hollenbeck, M.D..
Duke University, Durham, NC, USA.

PURPOSE
Fat grafting is a common adjunct procedure in breast reconstruction. While shown to have a safe oncologic profile, it may result in the development of palpable masses on physical exam, prompting further investigation with imaging and biopsy. The aim of this study was to assess the influence of fat grafting on the incidences of palpable masses, imaging, and biopsies after post-mastectomy breast reconstruction.
METHODS
Patients who underwent autologous or implant-based reconstruction following mastectomy from 2010-2018 were identified. Those receiving fat grafting as part of their reconstructive course were propensity matched in a 1:1 ratio to those that did not undergo a fat grafting procedure with BMI, reconstruction timing, and reconstruction type as covariates in a multivariable logistic regression model.
RESULTS
A total of 186 patients were identified, yielding 93 propensity-matched pairs (Table 1). Patients that underwent fat grafting had higher incidences of palpable masses (38.0% vs. 18.3%; p=0.003) and post-reconstruction imaging (47.3% vs. 29.0%; p=0.01). However, there was no significant difference in the number of biopsies performed between patients who did and did not receive fat grafting (11.8% vs. 7.5%; p=0.32). When looking at imaging characteristics amongst the fat grafted cohort, imaging was predominately interpreted as normal (BIRADS 1, 27.9%) or benign (BIRADS 2, 48.8%), with fat necrosis being the most common finding (n=20, 45.5%) (Table 2). No demographic, oncologic, reconstructive, or fat grafting-specific variables were independently predictive of receiving post-reconstruction imaging in multivariate analysis when controlling for follow-up time. On Kaplan-Meier analysis, fat grafting was not associated with decreased 5-year overall survival (Figure 1, left) or locoregional recurrence-free survival (Figure 1, right).
CONCLUSIONS
Fat grafting to the reconstructed breast is associated with increased incidences of palpable masses and subsequent post-reconstruction imaging. However, fat grafted patients do not undergo more biopsies, owing to the successful identification of fat-related changes on imaging. Thus, patients should be counseled in the preoperative period that they may be more likely to detect a palpable mass following fat grafting, and may be subject to more diagnostic imaging. Patients should be reassured, however, that fat grafting has a safe oncologic profile and does not affect overall or locoregional recurrence-free survival.

Table 1: Patient Characteristics
Was Fat Grafting Performed?
No(N=93)Yes(N=93)Total(N=186)P-value
Age at Mastectomy (in years)0.35871
Mean (SD)49.9 (9.68)48.7 (9.26)49.3 (9.47)
Median49.848.349.2
Range27.3, 71.630.5, 69.127.3, 71.6
Follow-up Since Mastectomy (years)0.31812
Mean (SD)4.1 (2.50)4.4 (2.44)4.2 (2.47)
Race/Ethnicity, n (%)0.64403
White72 (78.3%)73 (78.5%)145 (78.4%)
African American15 (16.3%)12 (12.9%)27 (14.6%)
Hispanic/Latino0 (0.0%)1 (1.1%)1 (0.5%)
Other or Unspecified5 (5.4%)7 (7.5%)12 (6.5%)
Missing101
BMI at Mastectomy, n (%)1.00003
under 2528 (30.1%)28 (30.1%)56 (30.1%)
25-3037 (39.8%)37 (39.8%)74 (39.8%)
over 3028 (30.1%)28 (30.1%)56 (30.1%)
Diabetes, n (%)5 (5.4%)6 (6.5%)11 (5.9%)0.75593
Smoker, n (%)5 (5.4%)7 (7.5%)12 (6.5%)0.55063
Cancer Stage, n (%)
I37 (39.8%)36 (38.7%)73 (39.2%)
IIA23 (24.7%)25 (26.9%)48 (25.8%)
IIB15 (16.1%)13 (14.0%)28 (15.1%)
IIIA12 (12.9%)14 (15.1%)26 (14.0%)
IIIB4 (4.3%)0 (0.0%)4 (2.2%)
IIIC2 (2.2%)5 (5.4%)7 (3.8%)
Neoadjuvant Chemo, n (%)40 (44.0%)34 (37.0%)74 (40.4%)0.33473
Adjuvant Chemo, n (%)37 (40.2%)31 (35.6%)68 (38.0%)0.52763
Neoadjuvant RT, n (%)4 (4.3%)6 (6.6%)10 (5.5%)0.50403
Adjuvant RT, n (%)46 (50.5%)45 (51.1%)91 (50.8%)0.93743
Mastectomy Type, n (%)0.48903
Nipple sparing mastectomy10 (10.8%)17 (18.3%)27 (14.5%)
Skin sparing mastectomy12 (12.9%)11 (11.8%)23 (12.4%)
Simple mastectomy46 (49.5%)45 (48.4%)91 (48.9%)
Modified radical mastectomy25 (26.9%)20 (21.5%)45 (24.2%)
Mastectomy Laterality, n (%)1.00003
Unilateral42 (45.2%)42 (45.2%)84 (45.2%)
Bilateral51 (54.8%)51 (54.8%)102 (54.8%)
BRCA +, n (%)13 (14.0%)10 (10.8%)23 (12.4%)0.50403
ER+, n (%)71 (76.3%)75 (80.6%)146 (78.5%)0.47533
PR+, n (%)56 (60.2%)66 (71.0%)122 (65.6%)0.12273
HER2+, n (%)24 (25.8%)18 (19.4%)42 (22.6%)0.29273
Triple Negative, n (%)16 (17.2%)13 (14.0%)29 (15.6%)0.54433
Reconstruction Type, n (%)1.00003
Autologous67 (72.0%)67 (72.0%)134 (72.0%)
Implant-based26 (28.0%)26 (28.0%)52 (28.0%)
Reconstruction Timing, n (%)0.91203
Immediate39 (41.9%)36 (39.1%)75 (40.5%)
Delayed54 (58.1%)56 (60.2%)110 (59.1%)
Missing011
Flap Type, n (%)
DIEP36 (53.7%)44 (65.7%)80 (59.7%)
TRAM (free)6 (9.0%)7 (10.4%)13 (9.7%)
MS-TRAM (free)13 (19.4%)15 (22.4%)28 (20.9%)
SIEA0 (0.0%)1 (1.5%)1 (0.7%)
Latissimus dorsi5 (7.5%)0 (0.0%)5 (3.7%)
Other7 (10.4%)0 (0.0%)7 (5.2%)
Missing262652
Follow-up Since Reconstruction (years)0.18242
Mean (SD)3.3 (2.34)3.7 (2.34)3.5 (2.34)
Palpable Mass on Exam, n (%)17 (18.3%)35 (38.0%)52 (28.1%)0.00283
Post-Reconstruction Imaging,
n (%)
27 (29.0%)44 (47.3%)71 (38.2%)0.01033
Post-Reconstruction Biopsy, n (%)7 (7.5%)11 (11.8%)18 (9.7%)0.32123
1t-test; 2Wilcoxon rank sum p-value; 3Chi-Square p-value; Chemo-chemotherapy; RT-radiation therapy; DIEP-deep inferior epigastric artery perforator flap; TRAM-transverse rectus abdominis myocutaneous flap; MS-TRAM-muscle sparing transverse rectus abdominis myocutaneous flap; SIEA-superficial inferior epigastric artery flap

Table 2: Characteristics of Imaging and Biopsy Events in the Imaged Subset
Was Fat Grafting Performed?
No(N=27)Yes(N=44)Total(N=71)P-value
Total Number of Post-Reconstruction Imaging Events0.30171
Mean (SD)1.8 (0.93)2.2 (1.39)2.0 (1.24)
Median2.02.02.0
Range1.0, 4.01.0, 6.01.0, 6.0
Imaging Type, n (%)0.26782
Ultrasound8 (29.6%)6 (13.6%)14 (19.7%)
MRI4 (14.8%)5 (11.4%)9 (12.7%)
Mammogram2 (7.4%)8 (18.2%)10 (14.1%)
> 1 Type13 (48.1%)25 (56.8%)38 (53.5%)
BI-RADS Score, n (%)
18 (33.3%)12 (27.9%)20 (29.9%)
212 (50.0%)21 (48.8%)33 (49.3%)
30 (0.0%)3 (7.0%)3 (4.5%)
44 (16.7%)7 (16.3%)11 (16.4%)
Missing314
Radiologic Interpretation of Imaging, n (%)
Normal15 (55.6%)14 (31.8%)29 (40.8%)
Fat necrosis4 (14.8%)20 (45.5%)24 (33.8%)
Other benign finding5 (18.5%)5 (11.4%)10 (14.1%)
Recurrence2 (7.4%)3 (6.8%)5 (7.0%)
Multiple1 (3.7%)2 (4.5%)3 (4.2%)
Pathological Interpretation of Biopsy, n (%)
Fat necrosis2 (33.3%)3 (27.3%)5 (29.4%)
Oil cyst0 (0.0%)1 (9.1%)1 (5.9%)
Normal0 (0.0%)1 (9.1%)1 (5.9%)
Malignancy2 (33.3%)*3 (27.3%)5 (29.4%)
Other benign finding2 (33.3%)3 (27.3%)5 (29.4%)
Provider Who Ordered Imaging/Biopsy, n (%)
PCP1 (3.8%)2 (4.5%)3 (4.3%)
Breast Surgeon2 (7.7%)9 (20.5%)11 (15.7%)
Breast Oncologist21 (80.8%)31 (70.5%)52 (74.3%)
Other0 (0.0%)1 (2.3%)1 (1.4%)
Multiple2 (7.7%)1 (2.3%)3 (4.3%)
Missing101
1Wilcoxon rank sum p-value; 2Chi-Square p-value
*An additional patient with biopsy-proven recurrence who did not receive preceding imaging is not included in the table.

Figure 1: Kaplan-Meier Probability for Overall Survival (left) and Locoregional Recurrence-Free Survival (right)


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