Purpose / Objectives: In patients with macromastia, breast conservation surgery (BCS) followed by radiation therapy (RT) for the treatment of breast cancer may be associated with a different complication profile than those without macromastia. General complications of BCS followed by RT includes seroma, infection, wound complications, cosmetic deformity, asymmetry, acute versus long term arm and/or breast lymphedema. Oncoplastic reduction mammoplasty (ORM) aims to reduce breast volume while excising the tumor bed and its margins. Since breast volume was found to be a risk factor for chronic breast lymphedema, this study was performed to determine the impact of ORM on chronic breast lymphedema as well as other complications compared to BCS without ORM. Materials / Methods: We performed a retrospective chart review on patients who underwent lumpectomy with RT from 2014 to 2018. Chronic breast lymphedema (CBL) was defined as swelling that persisted >1 year post-RT. Breast volumes (BV) were determined by contoured breast volumes or, if unavailable, estimated by the 95% isodose volumes from the RT treatment planning system. Univariate analysis was used to evaluate various patient factors and treatment outcomes in women with BV ≥1300 cc compared to <1300 cc. These same factors were compared in women who underwent ORM vs. BCS alone. Multivariate regression analysis was used to evaluate factors associated with ≥1 complication. Logistic regression was performed to identify factors associated with the development of CBL. Results: The total population included 1173 patients, of which 51 (4.3%) underwent ORM and 1122 (95.7%) underwent BCS. 440 (37.5%) patients had BV ≥1300 cc and 733 (62.5%) patients had a BV <1300 cc. Multivariate regression analysis demonstrated that patients with BV ≥1300 cc had a higher BMI (OR=1.200, P<0.001), decreased risk of grade 2 radiation dermatitis (OR=0.457, P=0.002), and increased risk of CBL (OR=2.127, P=0.024) compared to patients with BV <1300 cc. However, oncoplastic reduction was associated with an increased risk of hematoma (OR=5.934, P<0.001), increased risk of wound dehiscence (OR=12.433, P<0.001), and decreased risk of seroma (OR=0.201, P<0.001) compared to BCS patients. Conclusions: Our data demonstrates that patients with breast volume > 1300 cc are at increased risk for developing several complications regardless of the presence of ORM. Those who had ORM experienced an increase in wound complications but having undergone ORM appeared to eliminate the increased risk of CBL associated with macromastia. This suggests that ORM should be considered at the time of BCS to reduce their future risk of CBL as there is no cure for this disease. Citation Format: Jenna Nicole Luker, Cara Canella, Sanjay Rama, Kelley Park, Renee Barry, Saheli Ghosh, Simeng Zhu, Yalei Chen, Jessica Bensenhaver, Eleanor Walker, Kenneth Levin, Maristella Evangelista, Dunya Atisha. The effect of oncoplastic reduction on the incidence of post-operative breast lymphedema in breast cancer patients undergoing lumpectomy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-49.

Purpose/Objective(s):Unlike temporary breast edema caused by post-lumpectomy radiation therapy (RT), the edema that persists beyond one year is not well defined and difficult to treat. The aim of this study is to define the incidence and risk factors for the development of chronic breast lymphedema in women undergoing lumpectomy with RT at a large metropolitan cancer center. Materials/Methods:A retrospective chart review was performed on all patients who underwent lumpectomy from 2014 to 2018. Women who did not undergo RT at our institution and those with stage IV disease were excluded from the analysis. Patient demographics, comorbidities, operative data, RT data and postoperative complications were obtained. Chronic breast lymphedema (CBL) was defined as edema that persisted beyond one year post completion of radiation therapy. Breast volumes were determined by contoured breast volumes or, if unavailable, estimated by the 95% isodose volumes from the RT treatment planning system. Using a density curve, the distribution of breast volumes was plotted for patients with and patients without CBL. Univariate analysis was used to evaluate factors associated with CBL. Multivariate regression analysis was used to evaluate factors associated with the risk of CBL while accounting for potential confounding variables as defined by the univariate analysis. Results:A total of 1173 patients were included for analysis. Seventy-four (6.3%) patients developed breast lymphedema beyond one year. For the entire cohort, mean age was 63 years old (SD=11.17), mean BMI was 31.15 kg/m2 (SD=7.17), mean breast volume was 1198.54 cm3 (SD=645.82 cm3), mean total radiation was 59.18 Gy (SD=16.76), and 139 (11.8%) patients underwent ALND. Compared to the cohort that did not develop CBL (n=1099), the CBL cohort (n=74) had a higher median BMI (33.23 kg/m2 vs. 29.81 kg/m2, P<0.001), higher percentage of African Americans (56.8% vs. 37.9%, P=0.004), larger median breast volume (1502.33 cm3 vs. 1083.59 cm3, P<0.001), higher percentage that underwent ALND (23% vs. 11.1%, P=0.005), and larger median size of lumpectomy specimen (128.00 cm3 vs. 94.57 cm3, P=0.002). When accounting for potential confounding variables, multivariate regression analysis revealed when breast volume was evaluated as a continuous variable, for every 1 cm3 increase in breast volume, the risk of breast lymphedema increases by 0.1% (OR=1.001, P<0.001). When breast volume was analyzed as a categorical variable using 1300 cm3 as the optimal cutoff (based on density curve evaluations), patients whose breast volume was greater than 1300 cm3 had nearly 3 times the risk of developing CBL (OR=2.976, P<0.001) compared to those with less than 1300 cm3 breast volume. The multivariate regression also demonstrated that CBL was associated with total radiation dose (OR=1.02, P=0.015) and African American race (OR=1.705, P=0.037). Conclusion:Chronic breast lymphedema presents a clinical concern for women undergoing lumpectomy with postoperative radiation, particularly in women with larger breasts. Further studies should focus on preventative strategies, as well as the psychosocial and economic impact of this morbidity. Citation Format: Sanjay Rama, Cara Canella, Jenna Luker, Kelley Park, Renee Barry, Saheli Ghosh, Simeng Zhu, Yalei Chen, Jessica Bensenhaver, Eleanor Walker, Kenneth Levin, Dunya Atisha, Maristella Evangelista. Factors associated with chronic breast lymphedema after adjuvant radiation in women undergoing breast conservation therapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-12.

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