Modeling AeroForm tissue expander for postmastectomy radiation therapy

Air Versus Saline in Tissue Expanders: A Systematic Review of the Literature

BACKGROUND

 There has been a greater focus in recent literature proposing air to be a superior medium to saline in tissue expanders. This study aims to review the literature and assess the quality of data on the efficacy and safety of air as an alternative medium to saline in tissue expanders, in the setting of postmastectomy two-stage reconstruction.

METHODS

 A systematic review regarding air inflation of tissue expanders was conducted using PubMed, Embase, Cochrane Library, and Web of Science. The methods followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Three reviewers separately performed data extraction and comprehensive synthesis.

RESULTS

 A total of 427 articles were identified in our search query, of which 11 met the inclusion criteria. Three pertained to inflation with room air, and eight pertained to inflation with CO2 using the AeroForm device. They were comparable to decreased overall complication rates in the room air/CO2 cohort compared to saline, although statistical significance was only observed in one of five two-arm studies. Investigating specific complications in the five two-arm studies, significantly lower rates of skin flap necrosis were only observed in two CO2-based studies. Studies rarely discussed other safety profile concerns, such as the impacts of air travel, radiation planning, and air extravasation beyond descriptions of select patients within the cohort.

CONCLUSION

 There is insufficient evidence to suggest improved outcomes with room air inflation of tissue expanders. Further work is needed to fully characterize the benefits and safety profiles of air insufflation before being adopted into clinical practice.

Post-mastectomy Breast Reconstruction With Gas vs Saline Tissue Expanders: Does the Fill Type Matter?

The most common reconstruction technique following mastectomy is a 2-stage technique that involves tissue expansion followed by definitive implant-based reconstruction (IBR). Tissue expanders (TEs) have classically used saline for initial fill; however, TEs with an initial gas fill (GTE)-including the CO2-based AeroForm (AirXpanders, San Francisco, CA) TE and TEs initially filled with atmospheric air-have been increasingly used in the past decade. We aimed to compare the outcomes in breast reconstruction for tissue expanders initially filled with saline vs gas. PubMed was queried for studies comparing gas- and saline-filled tissue expanders (STEs) used in IBR. A meta-analysis was performed on major postoperative outcomes and the required expansion and definitive reconstruction time. Eleven studies were selected and included in the analysis. No significant differences existed between tissue expansion with GTEs vs STEs for 11 of the 13 postoperative outcomes investigated. Out of the complications investigated, only the risk of infection/cellulitis/abscess formation was significantly lower in the GTE cohort (odds ratio 0.62; 95% CI, 0.47 to 0.82; P = .0009). The time to definitive reconstruction was also significantly lower in the GTE cohort (mean difference [MD], 45.85 days; 95% CI, -57.80 to -33.90; P < .00001). The total time to full expansion approached significance in the GTE cohort (MD, -20.33 days; 95% CI, -41.71 to 1.04; P = .06). A cost analysis considering TE cost and infection risk determined that GTE use saved a predicted $2055.34 in overall healthcare costs. Surgical outcomes for both fill types were predominantly similar; however, GTEs were associated with a significantly decreased risk of postoperative infection compared to saline-filled TEs. GTEs could also reduce healthcare expenditures and require less time until definitive reconstruction after placement.

LEVEL OF EVIDENCE: 3

The effect of material assignment in nasal cavity on dose calculation for nasopharyngeal carcinoma (NPC) using Acuros XB

PURPOSE

To evaluate the effect of material assignment in nasal cavity on dose calculation for the volumetric modulated arc therapy (VMAT) of nasopharyngeal carcinoma (NPC) using Acuros XB (AXB) algorithm.

METHODS

The VMAT plans of 30 patients with NPC were calculated using AXB with material auto-assignment of nasal cavity to lung and reassignment to air respectively. The doses to the planning target volumes (PTVs) overlapping with nasal cavity with material auto-assignment of lung (AXB_Lung) were compared to the values obtained when nasal cavity was reassigned to air (AXB_Air) under the dose-to-medium (D_m ) reporting mode of AXB.

RESULTS

For dose calculated under AXB_Lung, the D_98% , D_2% , and D_mean of the PTV_69.96 _Air Cavity (PTV of prescription dose 69.96 Gy overlapping with nasal cavity) were on average 16.1%, 1.6%, and 8.6% larger than that calculated under AXB_Air, respectively. Up to 19.5% difference in D_98% , 3% difference in D_2% , and 11.2% difference in D_mean were observed in the worst cases for PTV_69.96 . Similar trend was observed for the PTV₅₉₄₀ _Air Cavity, in which the D_98% , D_2% , and D_mean calculated under AXB_Lung were on average 14.7%, 2.5%, and 10.2% larger than that calculated under AXB_Air, respectively. In the worst cases, the difference observed in D_98% , D_2% , and D_mean could be up to 17.7%, 4.5%, and 12.7%, respectively.

CONCLUSIONS

Significant dose difference calculated by AXB between the material assignment of lung and air in nasal cavity for NPC cases might imply the possibility of underdosage to the PTVs that overlap with inhomogeneity. Therefore, attention should be put to ensure that accurate material assignment for dose calculation under AXB such that optimal dosage was given for tumor control.