Changes in Skin Vascularity in a Murine Model for Postmastectomy Radiation

A Paradigm Shift: Outcomes of Early Autologous Breast Reconstruction after Radiation Therapy

BACKGROUND

 Radiation creates significant challenges for breast reconstruction. There is no consensus regarding optimal timing for autologous reconstruction following radiation. This study explores clearly defined, shorter time intervals between completion of radiation and reconstruction than previously reported.

METHODS

 A retrospective review was performed on patients who underwent autologous reconstruction by five microsurgeons at an academic institution from 2009 to 2020. Cohorts were selected by time elapsed between radiation and autologous reconstruction including <3 months, 3 to 6 months, 6 to 9 months, 9 to 12 months, 12 to 24 months, and >24 months. Analysis compared baseline characteristics, operative details, complications, revision rates, and BREAST-Q scores. Analysis of variance was used for continuous variables and chi-square for discrete variables.

RESULTS

 In total, 462 radiated patients underwent 717 flaps. There were 69 patients at <3 months (14.9%), 97 at 3 to 6 months (21%), 64 at 6 to 9 months (13.9%), 36 at 9 to 12 months (7.8%), 73 at 12 to 24 months (15.8%), and 123 at >24 months (26.6%). Age, time from mastectomy, and failure of primary reconstruction were higher at >24 months (p < 0.001). There was no difference between cohorts in intraoperative complications in radiated or nonradiated breasts. There was no difference in acute and late postoperative complications between cohorts. Wound-healing complications in radiated sides were lowest at <3 months and 3 to 6 months (5/69 [7.3%] and 11/97 [11.3%], respectively) compared with other groups (18.8-22.2%) but did not reach significance (p = 0.11). More fat graft revisions occurred at <3 months (p = 0.003).

CONCLUSION

 Reconstruction can be safely performed within 3 months after radiation without increases in intraoperative, acute, or late reconstructive complications.

The Biointegration of a Porcine Acellular Dermal Matrix in a Novel Radiated Breast Reconstruction Model

BACKGROUND

Ideal acellular dermal matrices (ADM) for breast reconstruction exhibit native extracellular matrix (ECM) structure to allow rapid biointegration and appropriate mechanical properties for desired clinical outcomes. In a novel in vivo model of irradiated breast reconstruction, we describe the cellular and vascular ingrowth of Artia, a porcine product chemically prepared to mimic the biomechanics of human ADM, with retained natural ECM structure to encourage cellular ingrowth.

METHODS

Utilizing the murine dorsal skinfold model, Artia was implanted into 16 C57bl/6 mice. Eight of the mice received a single dose 35 Gy radiation to the skin, followed by 12 weeks to produce radiation fibrosis and 8 mice served as nonradiated controls. Real-time photoacoustic microscopy of vascular integration and oxygen saturation within the ADM were made over 14 days. At 21 days, vascular ingrowth (CD31), fibroblast scar tissue formation (alpha smooth-muscle actin α-SMA, vimentin), and macrophage function (M2/M1 ratio) were evaluated. Scanning electron microscopy images of Artia were produced to help interpret the potential orientation of cellular and vascular ingrowth.

RESULTS

Repeated photoacoustic microscopy imaging demonstrated vascular ingrowth increasing over 14 days, with a commensurate increase in oxygen saturation within both radiated and nonradiated ADM-albeit at an insignificantly lower rate in the radiated group. By day 21, robust CD31 staining was seen that was insignificantly greater in the nonradiated group. Of the fibroblast markers, vimentin expression was significantly greater in the radiated group (P < 0.05). Macrophage lineage phenotype was consistent with remodeling physiology in both radiated and nonradiated groups. Scanning electron microscopy demonstrated transversely organized collagen fibrils with natural porous ECM structure to allow cellular ingrowth.

CONCLUSIONS

Artia demonstrates appropriate biointegration, with increased oxygen saturation by 14 days, consistent with the performance of other collagen substrates in this model. Radiation fibrosis resulted in higher vimentin expression yet did not impact macrophage phenotype while only modestly decreasing Artia biointegration suggesting that ADM may have a role in reconstructive efforts in a radiated setting. Taken together with its enhanced biomechanics, this porcine ADM product is well poised to be clinically applicable to breast reconstruction.

Amifostine Prophylaxis in Irradiated Breast Reconstruction: A Study of Oncologic Safety In Vitro

BACKGROUND

Indications for adjuvant radiation therapy (XRT) in breast cancer have expanded. Although highly effective, XRT damages surrounding tissues and vasculature, often resulting in delayed or compromised breast reconstruction. Thus, effective yet safe methods of radiation injury prophylaxis would be desirable. Amifostine is a Food and Drug Administration-approved radioprotectant; however, concerns about its potential to also protect cancer remain. The purpose of this study was to evaluate the oncologic safety of amifostine (AMF) in vitro and determine its effect on human breast cancer cells in the setting of XRT.

METHODS

One ER+/PR+/Her2- (MCF-7) and two ER-/PR-Her2- (MDA-MB-231, MDA-MB-468) breast cancer cell lines were investigated. Female fibroblasts were used as controls. Cells were treated with WR-1065, the active metabolite of AMF, 20 minutes before 0Gy, 10Gy, or 20Gy XRT. Live and dead cells were quantified; percent cell death was calculated.

RESULTS

WR-1065 treatment significantly preserved viability and reduced healthy female fibroblasts death after XRT compared with untreated controls. All three breast cancer cells lines exhibited radiosensitivity with substantial cell death. Cancer cells retained their radiosensitivity despite WR-1065 pretreatment, achieving the same degree of cell death as untreated controls.

CONCLUSIONS

This study demonstrated the proficiency of AMF to selectively protect healthy cells from XRT while breast cancer cells remained radiosensitive. These results support the oncologic safety of AMF in breast cancer in vitro. Further investigation is now warranted in vivo to ascertain the translational potential of using AMF as a radioprotectant to improve breast reconstruction after radiation treatment.

Blood Supply of Early Lung Adenocarcinomas in Mice and the Tumor-supplying Vessel Relationship: A Micro-CT Angiography Study

This study aimed to investigate the blood supply of early lung adenocarcinomas in mice and the relationship between tumors and their supplying vessels by using micro-CT. An early lung adenocarcinoma model was established in 10 female mice with subcutaneous injections of a 1-methyl-3-nitro-1-nitrosoguanidine solution. Micro-CT pulmonary and bronchial arteriography were performed to demonstrate the blood supply of early lung adenocarcinomas, especially the tumor-vessel relationships, and the findings were correlated with the pathology results. The quantitative and texture changes in the tumor-supplying vessels were analyzed. Micro-CT showed that the pulmonary artery was densely distributed in and around tumors in 141 (84%) of 167 early lung adenocarcinomas, the bronchial artery was not related to tumors, and there were four patterns of tumor-pulmonary artery relationships that correlated well with pathologic findings. Quantitative and texture analyses showed that the tumor size had positive correlations with vessel volume (VV), VV fraction (VVF), vessel thickness (VT), vessel number (VN), inverse difference moment, long run emphasis, gray level nonuniformity (GLN), and run length nonuniformity (RLN) and negative correlations with vessel separation (VS), inertia, and short run emphasis (SRE); the size of the solid component had positive correlations with VV, VVF, VT, VN, GLN, and RLN and negative correlations with VS, cluster shade, and SRE. This study concluded that early lung adenocarcinomas are mainly supplied by the pulmonary arteries in mice, and micro-CT angiography can clearly demonstrate the morphologic changes of pulmonary arteries and their relationships with tumors.

Therapeutic Interventions to Reduce Radiation Induced Dermal Injury in a Murine Model of Tissue Expander Based Breast Reconstruction

BACKGROUND

Radiation therapy (XRT) induced dermal injury disrupts type I collagen architecture. This impairs cutaneous viscoelasticity, which may contribute to the high rate of complications in expander-based breast reconstruction with adjuvant XRT. The objective of this study was to further elucidate the mechanism of radiation-induced dermal injury and to determine if amifostine (AMF) or deferoxamine (DFO) mitigates type I collagen injury in an irradiated murine model of expander-based breast reconstruction.

METHODS

Female Lewis rats (n = 20) were grouped: expander (control), expander-XRT (XRT), expander-XRT-AMF (AMF), and expander-XRT-DFO (DFO). Expanders were surgically placed. All XRT groups received 28 Gy of XRT. The AMF group received AMF 30 minutes before XRT, and the DFO group used a patch for delivery 5 days post-XRT. After a 20-day recovery period, skin was harvested. Atomic force microscopy and Raman spectroscopy were performed to evaluate type I collagen sheet organization and tissue compositional properties, respectively.

RESULTS

Type I collagen fibril disorganization was significantly increased in the XRT group compared with the control (83.8% vs 22.4%; P = 0.001). Collagen/matrix ratios were greatly reduced in the XRT group compared with the control group (0.49 ± 0.09 vs 0.66 ± 0.09; P = 0.017). Prophylactic AMF demonstrated a marked reduction in type I collagen fibril disorganization on atomic force microscopy (15.9% vs 83.8%; P = 0.001). In fact, AMF normalized type I collagen organization in irradiated tissues to the level of the nonirradiated control (P = 0.122). Based on Raman spectroscopy, both AMF and DFO demonstrated significant differential protective effects on expanded-irradiated tissues. Collagen/matrix ratios were significantly preserved in the AMF group compared with the XRT group (0.49 ± 0.09 vs 0.69 ± 0.10; P = 0.010). β-Sheet/α-helix ratios were significantly increased in the DFO group compared with the XRT group (1.76 ± 0.03 vs 1.86 ± 0.06; P = 0.038).

CONCLUSIONS

Amifostine resulted in a significant improvement in type I collagen fibril organization and collagen synthesis, whereas DFO mitigated abnormal changes in collagen secondary structure in an irradiated murine model of expander-based breast reconstruction. These therapeutics offer the ability to retain the native microarchitecture of type I collagen after radiation. Amifostine and DFO may offer clinical utility to reduce radiation induced dermal injury, potentially decreasing the high complication rate of expander-based breast reconstruction with adjuvant XRT and improving surgical outcomes.

Effect of Radiation on DCE-MRI Pharmacokinetic Parameters in a Rabbit Model of Compromised Maxillofacial Wound Healing: A Pilot Study

PURPOSE

Osteoradionecrosis (ORN), a potentially debilitating complication of maxillofacial radiation, continues to present a challenging clinical scenario, with limited treatment options that often fail. Translational animal models that can accurately mimic the human characteristics of the condition are lacking. In the present pilot study, we aimed to characterize the effects of radiation on the dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) pharmacokinetic parameters in a rabbit model of compromised maxillofacial wound healing to determine its potential as a translational model of ORN.

MATERIALS AND METHODS

An experimental group underwent fractionated radiation of the mandible totaling 36 Gy. At 4 weeks after irradiation, the experimental and control groups (n = 8 rabbits each) underwent a surgical procedure to create a critical size defect in the mandibular bone. DCE-MRI scans were acquired 1 week after arrival (baseline; time point 1), 4 weeks after completion of irradiation in the experimental group (just before surgery, time point 2), and 4 weeks after surgery (time point 3).

RESULTS

No differences in the analyzed DCE-MRI parameters were noted within the experimental or control group between the baseline values (time point 1) and those after irradiation (time point 2). The whole blood volume fraction (v_b) in the experimental group was increased compared with that in the control group after irradiation (time point 2; P < .05). After surgery (time point 3), both the forward flux rate of contrast from blood plasma and the extracellular extravascular space and the v_b were increased in the control group compared with the experimental group (P < .05).

CONCLUSIONS

The results of the present study suggest that DCE-MRI of a rabbit model of compromised maxillofacial wound healing could reflect the DCE-MRI characteristics of human patients with ORN and those at risk of developing the condition. Future studies will focus on further characterization of this rabbit model as a translational preclinical model of ORN.

The Role of Deferoxamine in Irradiated Breast Reconstruction: A Study of Oncologic Safety

BACKGROUND

Radiotherapy plays an essential role in the oncologic management of breast cancer. However, patients who undergo radiotherapy experience significantly more wound complications during the reconstructive process. Deferoxamine has immense potential to up-regulate angiogenesis and improve reconstructive outcomes. The purpose of this study was to determine the impact of deferoxamine on breast cancer cell proliferation in vitro, to delineate oncologic safety concerns regarding the use of deferoxamine as a regenerative therapeutic.

METHODS

The dose-dependent effect of radiation and deferoxamine on two triple-negative breast cancer cell lines (MDA-MB-231 and MDA-MB-468) was determined by means of MTS (percentage cell viability) and tumorsphere (sphere number) analysis. Radiation therapy and deferoxamine were delivered both individually and in combination, and all experiments were completed in triplicate. Intracellular iron, nuclear factor-κB localization, and apoptosis/necrosis assays were performed to delineate mechanism. Analysis of variance statistical analysis was performed using SPSS (p < 0.05).

RESULTS

For both cell lines, percentage viability and sphere number significantly decreased following exposure to 10 Gy of radiation. Surprisingly, the administration of 25 µM deferoxamine also significantly decreased each metric. The administration of deferoxamine (100 µM) in combination with radiation (10 Gy) resulted in significantly reduced percentage viability and sphere number compared with the administration of radiation alone. Deferoxamine treatment decreased intracellular iron, suppressed nuclear factor-κB activation, and induced apoptosis.

CONCLUSION

Radiation and deferoxamine significantly decrease breast cancer proliferation when delivered independently and in combination, suggesting deferoxamine may be safely used to facilitate improved reconstructive outcomes among triple-negative breast cancer survivors.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

International multidisciplinary expert panel consensus on breast reconstruction and radiotherapy

BACKGROUND

Conflicting evidence challenges clinical decision-making when breast reconstruction is considered in the context of radiotherapy. Current literature was evaluated and key statements on topical issues were generated and discussed by an expert panel at the International Oncoplastic Breast Surgery Meeting in Milan 2017.

METHODS

Studies on radiotherapy and breast reconstruction (1985 to September 2017) were screened using MEDLINE, Embase and CENTRAL. The literature review yielded 30 controversial key questions. A set of key statements was derived and the highest levels of clinical evidence (LoE) for each of these were summarized. Nineteen panellists convened for dedicated discussions at the International Oncoplastic Breast Surgery Meeting to express agreement, disagreement or abstention for the generated key statements.

RESULTS

The literature review identified 1522 peer-reviewed publications. A list of 22 key statements was produced, with the highest LoE recorded for each statement. These ranged from II to IV, with most statements (11 of 22, 50 per cent) supported by LoE III. There was full consensus for nine (41 per cent) of the 22 key statements, and more than 75 per cent agreement was reached for half (11 of 22).

CONCLUSION

Poor evidence exists on which to base patient-informed consent. Low-quality studies are conflicting with wide-ranging treatment options, precluding expert consensus regarding optimal type and timing of breast reconstruction in the context of radiotherapy. There is a need for high-quality evidence from prospective registries and randomized trials in this field.

A Novel Small-Animal Model of Irradiated, Implant-Based Breast Reconstruction

BACKGROUND

There is currently a need for a clinically relevant small-animal model for irradiated, implant-based breast reconstruction. Present models are inadequate in terms of suboptimal location of expander placement and mode of radiation delivery, correlating poorly with the human clinical scenario. The authors hypothesized that by delivering fractionated radiation and placing an expander under the scalp of the animal, they would achieve soft-tissue changes histologically analogous to those seen in human irradiated, implant-based breast reconstruction.

METHODS

This study consisted of 11 immunocompetent, hairless rats divided into three groups as follows: untreated control (n = 3), tissue-expanded scalps (n = 4), and fractionated irradiation plus tissue expansion of the scalp (n = 4). At the completion of the experiment for each group, skin tissue samples were analyzed histologically for vascularity, epidermal and dermal thickness, and collagen fiber alignment or scar formation.

RESULTS

Expanded rat epidermis was significantly thicker and dermis was more vascular than nonexpanded skin. The authors observed a greater degree of collagen fiber alignment in the expanded group compared with nonexpanded skin. The combination of irradiation and expansion resulted in significant dermal thinning, vascular depletion, and increased scar formation compared with expanded skin alone.

CONCLUSIONS

The authors describe a novel small-animal model for irradiated, implant-based breast reconstruction where histologic analysis shows structural changes in the skin consistent with known effects of radiation therapy and expansion in human skin. This model represents a significant improvement from previous ones and, as such, holds the potential to be used to test new therapeutic agents to improve clinical outcomes.