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Poster lunch

1939 - Evaluation of Tissue Computed Tomography Number Changes and Dosimetric Shifts after Conventionally Fractionated Irradiation in Patients Undergoing Breast Conserving Surgery (79P)

Date

18 Nov 2017

Session

Poster lunch

Topics

Staging Procedures (not Imaging);  Surgical Oncology;  Radiation Oncology;  Breast Cancer

Presenters

Dong Soo Lee

Citation

Annals of Oncology (2017) 28 (suppl_10): x16-x24. 10.1093/annonc/mdx655

Authors

D.S. Lee1, Y.K. Lee1, J.S. Kim2, J. Lee1, Y.S. Kim2

Author affiliations

  • 1 Department Of Radiation Oncology, College of Medicine, The Catholic University of Korea, 113 - Seoul/KR
  • 2 Department Of General Surgery, College of Medicine, The Catholic University of Korea, 113 - Seoul/KR
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Resources

Abstract 1939

Background

The aim of this study was to assess tissue computed tomography (CT) number changes and corresponding dosimetric shifts in repeatedly performed simulation CT (re-sim CT) scans after conventionally fractionated irradiation in breast cancer patients.

Methods

A total of 28 breast cancer patients who underwent breast conserving surgery were enrolled in this study. All patients had received 50.4 Gy of conventionally fractionated irradiation and underwent re-sim CT scans for tumor bed boost. For evaluation of dosimetric shifts between initial and re-sim CT scans, electron boost plans in the same field size, same monitor unit with source-to-skin distance (SSD) 100cm were conducted. Dosimetric parameters (D105%, D103%, D100%, D98%, D95%, D90%: Dx% indicates volumes which receive X% of prescribed doses) between initial and re-sim CT scans were compared. The CT number data (CTmean, CTmax, CTmin) of original and irradiated CT (re-sim CT) scans from each representative structure (lung, rib bone, soft tissue, muscle, etc) were examined and recruited.

Results

CT numbers showed highly variable changes. Soft tissue CTmean and muscle CTmax/CTmin showed statistically and significantly increased values in re-sim CT compared with original CT scans. Rib bone CTmean/CTmin showed statistically and significantly decreased values in re-sim CT compared with original CT scans. Other CT number values showed no statistically significant changes. Among dosimetric parameters, only D105% (p = 0.015, mean 3.07cc versus 1.63cc) and D103% (p = 0.017, mean 13.8cc versus 11.9cc) showed statistically increased values in re-sim CT compared with original CT scans.

Conclusions

CT number changes after conventionally fractionated irradiation were different according to the tissue component. For electron boost plans, implementation of re-sim CT might be considered because significant dosimetric factor changes were observed especially in the high dose areas (hot spots; D105% andD103%).

Clinical trial identification

Legal entity responsible for the study

CMC IRB Ethics Committee

Funding

None

Disclosure

All authors have declared no conflicts of interest.

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