title: Comparative dosimetric findings using accelerated partial breast irradiation across five catheter subtypes.
abstract: OBJECTIVE
  Accelerated partial breast irradiation (APBI) with balloon and strut adjusted volume implants (SAVI) show promising results with excellent tumor control and minimal toxicity. Knowing the factors that contribute to a high skin dose, rib dose, and D95 coverage may reduce toxicity, improve tumor control, and help properly predict patient outcomes following APBI.
  
  
  METHODS
  A retrospective analysis of 594 patients treated with brachytherapy based APBI at a single institution from May 2008 to September 2014 was grouped by applicator subtype. Patients were treated to a total of 34 Gy (3.4 Gy x 10 fractions over 5 days delivered BID) targeting a planning target volume (PTV) 1.0 cm beyond the lumpectomy cavity using a high dose rate source.
  
  
  RESULTS
  SAVI devices had the lowest statistically significant values of DmaxSkin (81.00 ± 29.83), highest values of D90 (101.50 ± 3.66), and D95 (96.09 ± 4.55). SAVI-mini devices had the lowest statistically significant values of DmaxRib (77.66 ± 32.92) and smallest V150 (18.01 ± 3.39). Multi-lumen balloons were able to obtain the smallest V200 (5.89 ± 2.21). Strut-based applicators were more likely to achieve a DmaxSkin and a DmaxRib less than or equal to 100 %. The effect of PTV on V150 showed a strong positive relationship (p < .001). PTV and DmaxSkin showed a weak negative relationship in multi-lumen applicators (p = .016) and SAVI-mini devices (p < .001). PTV and DmaxRib showed a weak negative relationship in multi-lumen applicators (p = .009), SAVI devices (p < .001), and SAVI-mini devices (p < .001).
  
  
  CONCLUSIONS
  PTV volume is strongly correlated with V150 in all devices and V200 in strut based devices. Larger PTV volumes result in greater V150 and V200, which could help predict potential risks for hotspots and resulting toxicities in these devices. PTV volume is also weakly negatively correlated with max skin dose and max rib dose, meaning that as the PTV volumes increase one can expect slightly smaller max skin and rib doses. Strut based applicators are significantly more effective in keeping skin and rib dose constraints under 125 and 100 % when compared to any balloon based applicator.
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. zhrana88@gmail.com.
authors.forename: Zaker
authors.initials: Z
authors.lastname: Rana
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. nmnasr@gmail.com.
authors.forename: Nadim M
authors.initials: NM
authors.lastname: Nasr
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. HJi@virginiahospitalcenter.com.
authors.forename: Huaying
authors.initials: H
authors.lastname: Ji
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. VLorio@virginiahospitalcenter.com.
authors.forename: Virginia
authors.initials: V
authors.lastname: Lorio
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. sra2629@virginiahospitalcenter.com.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Akbari
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. mls2663@virginiahospitalcenter.com.
authors.forename: Molly
authors.initials: M
authors.lastname: Sebastian
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. mnm2037@virginiahospitalcenter.com.
authors.forename: Mami
authors.initials: M
authors.lastname: Martin
authors.affiliation: Department of Radiation Oncology, Virginia Hospital Center, 1701 N George Mason Dr, Arlington, VA, 22205, USA. rhong@virginiahospitalcenter.com.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Hong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000295:instrumentation*; D001943:Breast Neoplasms / Q000532:radiotherapy*; D057785:Catheters; D019583:Dose Fractionation, Radiation; D004867:Equipment Design; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D058958:Organs at Risk; D011832:Radiation Injuries / Q000517:prevention & control; D011874:Radiometry; D018714:Radiotherapy, Adjuvant / Q000295:instrumentation*; D012189:Retrospective Studies; D012272:Ribs / Q000528:radiation effects; D012867:Skin / Q000528:radiation effects; D047368:Tumor Burden