PMID- 26520757
OWN - NLM
STAT- MEDLINE
DCOM- 20160810
LR  - 20191210
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Linking)
VI  - 42
IP  - 11
DP  - 2015 Nov
TI  - A feasibility study: Selection of a personalized radiotherapy fractionation 
      schedule using spatiotemporal optimization.
PG  - 6671-8
LID - 10.1118/1.4934369 [doi]
AB  - PURPOSE: To investigate the impact of using spatiotemporal optimization, i.e., 
      intensity-modulated spatial optimization followed by fractionation schedule 
      optimization, to select the patient-specific fractionation schedule that 
      maximizes the tumor biologically equivalent dose (BED) under dose constraints for 
      multiple organs-at-risk (OARs). METHODS: Spatiotemporal optimization was applied 
      to a variety of lung tumors in a phantom geometry using a range of tumor sizes 
      and locations. The optimal fractionation schedule for a patient using the 
      linear-quadratic cell survival model depends on the tumor and OAR sensitivity to 
      fraction size (alpha/beta), the effective tumor doubling time (Td), and the size and 
      location of tumor target relative to one or more OARs (dose distribution). The 
      authors used a spatiotemporal optimization method to identify the optimal number 
      of fractions N that maximizes the 3D tumor BED distribution for 16 lung phantom 
      cases. The selection of the optimal fractionation schedule used equivalent 
      (30-fraction) OAR constraints for the heart (Dmean</=45 Gy), lungs (Dmean</=20 Gy), 
      cord (Dmax</=45 Gy), esophagus (Dmax</=63 Gy), and unspecified tissues (D05</=60 Gy). 
      To assess plan quality, the authors compared the minimum, mean, maximum, and D95 
      of tumor BED, as well as the equivalent uniform dose (EUD) for optimized plans to 
      conventional intensity-modulated radiation therapy plans prescribing 60 Gy in 30 
      fractions. A sensitivity analysis was performed to assess the effects of Td 
      (3-100 days), tumor lag-time (Tk=0-10 days), and the size of tumors on optimal 
      fractionation schedule. RESULTS: Using an alpha/beta ratio of 10 Gy, the average values 
      of tumor max, min, mean BED, and D95 were up to 19%, 21%, 20%, and 19% larger 
      than those from conventional prescription, depending on Td and Tk used. Tumor EUD 
      was up to 17% larger than the conventional prescription. For fast proliferating 
      tumors with Td less than 10 days, there was no significant increase in tumor BED 
      but the treatment course could be shortened without a loss in tumor BED. The 
      improvement in the tumor mean BED was more pronounced with smaller tumors 
      (p-value=0.08). CONCLUSIONS: Spatiotemporal optimization of patient plans has the 
      potential to significantly improve local tumor control (larger BED/EUD) of 
      patients with a favorable geometry, such as smaller tumors with larger distances 
      between the tumor target and nearby OAR. In patients with a less favorable 
      geometry and for fast growing tumors, plans optimized using spatiotemporal 
      optimization and conventional (spatial-only) optimization are equivalent 
      (negligible differences in tumor BED/EUD). However, spatiotemporal optimization 
      yields shorter treatment courses than conventional spatial-only optimization. 
      Personalized, spatiotemporal optimization of treatment schedules can increase 
      patient convenience and help with the efficient allocation of clinical resources. 
      Spatiotemporal optimization can also help identify a subset of patients that 
      might benefit from nonconventional (large dose per fraction) treatments that are 
      ineligible for the current practice of stereotactic body radiation therapy.
FAU - Kim, Minsun
AU  - Kim M
AD  - Department of Radiation Oncology, University of Washington, Seattle, Washington 
      98195-6043.
FAU - Stewart, Robert D
AU  - Stewart RD
AD  - Department of Radiation Oncology, University of Washington, Seattle, Washington 
      98195-6043.
FAU - Phillips, Mark H
AU  - Phillips MH
AD  - Departments of Radiation Oncology and Neurological Surgery, University of 
      Washington, Seattle, Washington 98195-6043.
LA  - eng
PT  - Evaluation Study
PT  - Journal Article
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
SB  - IM
MH  - Cell Survival/radiation effects
MH  - Dose Fractionation, Radiation
MH  - Esophagus/radiation effects
MH  - Feasibility Studies
MH  - Heart/radiation effects
MH  - Humans
MH  - Lung/pathology/radiation effects
MH  - Lung Neoplasms/pathology/radiotherapy
MH  - Models, Biological
MH  - Organs at Risk/radiation effects
MH  - Phantoms, Imaging
MH  - Precision Medicine/*methods
MH  - Radiometry
MH  - Radiotherapy, Intensity-Modulated/instrumentation/*methods
MH  - Spinal Cord/radiation effects
MH  - Tumor Burden
EDAT- 2015/11/02 06:00
MHDA- 2016/08/11 06:00
CRDT- 2015/11/02 06:00
PHST- 2015/11/02 06:00 [entrez]
PHST- 2015/11/02 06:00 [pubmed]
PHST- 2016/08/11 06:00 [medline]
AID - 10.1118/1.4934369 [doi]
PST - ppublish
SO  - Med Phys. 2015 Nov;42(11):6671-8. doi: 10.1118/1.4934369.