PMID- 10758332
OWN - NLM
STAT- MEDLINE
DCOM- 20000428
LR  - 20190708
IS  - 0360-3016 (Print)
IS  - 0360-3016 (Linking)
VI  - 47
IP  - 1
DP  - 2000 Apr 1
TI  - Optimization of beam weights in conformal radiotherapy planning of stage III 
      non-small cell lung cancer: effects on therapeutic ratio.
PG  - 255-60
AB  - PURPOSE: To evaluate the effects of beam weight optimization for 3D conformal 
      radiotherapy plans, with or without beam intensity modulation, in Stage III 
      non-small cell lung cancer (NSCLC). METHODS AND MATERIALS: Ten patients with 
      Stage III NSCLC were planned using a conventional 3D technique and a technique 
      involving noncoplanar beam intensity modulation (BIM). Two planning target 
      volumes (PTVs) were defined: PTV1 included macroscopic tumor volume and PTV2 
      included macroscopic and microscopic tumor volume. Virtual simulation defined the 
      beam shapes and incidences as well as the wedge orientations (3D) and segment 
      outlines (BIM). Weights of wedged beams, unwedged beams, and segments were 
      determined by human trial and error for the 3D-plans (3D-manual), by a standard 
      weight table (SWT) for the BIM-plans (BIM-SWT) and by optimization (3D-optimized 
      and BIM-optimized) using an objective function with a biological and a physical 
      component. The resulting non-optimized and optimized dose distributions were 
      compared, using physical endpoints, after normalizing the median dose of PTV1 to 
      80 Gy. RESULTS: Optimization improved dose homogeneity at the target for 3D- and 
      BIM-plans and the minimum dose at PTV1. The minimum dose at PTV2 was decreased by 
      optimization especially in 3D-plans. After optimization, the dose-volume 
      histograms (DVHs) of lung and heart were shifted to lower doses for 80-90% of the 
      organ volume. Since lung is the dose-limiting organ in Stage III NSCLC, an 
      increased minimum dose at PTV1 together with a decreased dose at the main lung 
      volume suggests an improved therapeutic ratio. Optimization allows 10% dose 
      escalation for 3D-plans and 20% for BIM-plans at isotoxicity levels of lung and 
      spinal cord. Upon dose escalation, esophagus may become the dose-limiting 
      structure when PTV1 extends close to the esophagus. CONCLUSIONS: Optimization 
      using a biophysical objective function allowed an increase of the therapeutic 
      ratio of radiotherapy planning for Stage III NSCLC.
FAU - De Gersem, W R
AU  - De Gersem WR
AD  - Division of Radiotherapy, University Hospital, Gent, Belgium.
FAU - Derycke, S
AU  - Derycke S
FAU - De Wagter, C
AU  - De Wagter C
FAU - De Neve, W C
AU  - De Neve WC
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Int J Radiat Oncol Biol Phys
JT  - International journal of radiation oncology, biology, physics
JID - 7603616
SB  - IM
CIN - Int J Radiat Oncol Biol Phys. 2001 Apr 1;49(5):1518-20. PMID: 11293435
MH  - Algorithms
MH  - Carcinoma, Non-Small-Cell Lung/pathology/*radiotherapy
MH  - Computer Simulation
MH  - Esophagus
MH  - Heart
MH  - Humans
MH  - Lung
MH  - Lung Neoplasms/pathology/*radiotherapy
MH  - Physical Phenomena
MH  - Physics
MH  - Radiotherapy Dosage
MH  - Radiotherapy Planning, Computer-Assisted/methods/*standards
MH  - Radiotherapy, Conformal/*standards
MH  - Spinal Cord
EDAT- 2000/04/12 09:00
MHDA- 2000/05/08 09:00
CRDT- 2000/04/12 09:00
PHST- 2000/04/12 09:00 [pubmed]
PHST- 2000/05/08 09:00 [medline]
PHST- 2000/04/12 09:00 [entrez]
AID - S0360-3016(99)00332-6 [pii]
AID - 10.1016/s0360-3016(99)00332-6 [doi]
PST - ppublish
SO  - Int J Radiat Oncol Biol Phys. 2000 Apr 1;47(1):255-60. doi: 
      10.1016/s0360-3016(99)00332-6.