Assessment of different IMRT boost delivery methods on target coverage and normal-tissue sparing

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Sequential boost techniques in radiation therapy involve treating initial and boost volumes separately.
• Intensity-modulated radiation therapy (IMRT) allows for precise dose delivery to complex target shapes.
• Simultaneous integrated boost (SIB) is an IMRT technique where initial and boost volumes are treated concurrently.

Purpose of the Study:

• To compare the efficacy of sequential versus simultaneous integrated boost IMRT techniques.
• To evaluate target coverage and normal-tissue sparing for different IMRT delivery methods.
• To assess the impact of SIB-IMRT on critical structure dose reduction in head-and-neck, lung, and prostate cancer.

Main Methods:

• Fifteen patients with head-and-neck, lung, and prostate cancer were included.
• Three IMRT plans were generated: sequential-IMRT(1) (3D-CRT + sequential IMRT), sequential-IMRT(2) (IMRT + sequential IMRT), and SIB-IMRT.
• Plans were compared using dose-volume histograms, D(100%), D(max), and D(mean) for target volumes and critical structures.

Main Results:

• SIB-IMRT demonstrated superior sparing of parotid glands in head-and-neck cases.
• SIB-IMRT significantly reduced mean spinal cord dose, rectal V(>70 Gy), bladder, rectum, and femur doses in prostate cases.
• SIB-IMRT lowered mean heart and esophagus doses and reduced lung V(20 Gy) in lung cancer cases compared to sequential techniques.

Conclusions:

• SIB-IMRT markedly reduced doses to critical structures compared to sequential IMRT techniques.
• SIB-IMRT plans exhibited superior conformality, potentially leading to lower doses in non-target tissues.
• The study suggests SIB-IMRT is an effective technique for improving normal-tissue sparing while maintaining target coverage.