Advances in radiation oncology · 2025
Dose Intensification to the Dominant Intraprostatic Lesion During Prostate Stereotactic Body Radiation Therapy Delivered on a Magnetic Resonance Imaging Linear Accelerator: Feasibility and Early Clinical Outcomes.
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Zelefsky Michael J, Byun David, Long Matthew, Fuligni Gabriel, Wang Hesheng, Lu Siming, Chen Ting, Barbee David
Аннотация
PURPOSE: This study aims to evaluate the feasibility of delivering escalated doses to the dominant intraprostatic lesion (DIL) as noted on T2-weighted magnetic resonance imaging and diffusion-weighted imaging while maintaining dose to the surrounding normal tissue structures within dose-volume constraints.
METHODS AND MATERIALS: A total of 50 consecutive patients were treated with prostate stereotactic body radiation therapy (SBRT), via a simultaneous integrated boost to the DIL, on a 1.5-Tesla magnetic resonance imaging linear accelerator platform. These patients were treated with SBRT to 40 Gy in 5 fractions every other day, and the DIL was simultaneously boosted to 45 Gy in 5 fractions. No patient was treated with androgen deprivation therapy. The normal tissue structures and the prostate and DIL were recontoured, and a postfraction plan was generated to retrospectively generate the doses delivered to the prostate and the DIL boost target for each of these 250 therapy sessions.
RESULTS: On postfraction dosimetric analysis, the median dose to 95% (D95) of the DIL was 45.3 Gy (initial plan: 45.9 Gy; P < .05), and 44 Gy or more was delivered to the DIL in 84% of the treated fractions. The median D95 to the prostate was 40.4 Gy (initial plan: 40.7 Gy; P < .05). Despite excellent target coverage, the rectum, urethra, and bladder dose constraints were generally maintained. At 6 months from completion of therapy, the median prostate-specific antigen result was 1.1 ng/mL (range, 0-5.6 ng/mL) compared to the median pre-SBRT prostate-specific antigen of 6.8 ng/mL (range, 3.45-31 ng/mL). No patient developed late grade 3 or higher urinary or rectal toxicities at median follow-up of 10.8 months (range, 6.4-15.7 months).
CONCLUSIONS: With real-time adaptive planning on a magnetic resonance imaging linear accelerator, dose escalation was achieved in most cases with the intended doses without significantly compromising the dose-volume constraints of the surrounding normal tissue structures. These dosimetric findings were associated with an excellent tolerance profile at 12 months and a low incidence of urinary or rectal toxicity.
METHODS AND MATERIALS: A total of 50 consecutive patients were treated with prostate stereotactic body radiation therapy (SBRT), via a simultaneous integrated boost to the DIL, on a 1.5-Tesla magnetic resonance imaging linear accelerator platform. These patients were treated with SBRT to 40 Gy in 5 fractions every other day, and the DIL was simultaneously boosted to 45 Gy in 5 fractions. No patient was treated with androgen deprivation therapy. The normal tissue structures and the prostate and DIL were recontoured, and a postfraction plan was generated to retrospectively generate the doses delivered to the prostate and the DIL boost target for each of these 250 therapy sessions.
RESULTS: On postfraction dosimetric analysis, the median dose to 95% (D95) of the DIL was 45.3 Gy (initial plan: 45.9 Gy; P < .05), and 44 Gy or more was delivered to the DIL in 84% of the treated fractions. The median D95 to the prostate was 40.4 Gy (initial plan: 40.7 Gy; P < .05). Despite excellent target coverage, the rectum, urethra, and bladder dose constraints were generally maintained. At 6 months from completion of therapy, the median prostate-specific antigen result was 1.1 ng/mL (range, 0-5.6 ng/mL) compared to the median pre-SBRT prostate-specific antigen of 6.8 ng/mL (range, 3.45-31 ng/mL). No patient developed late grade 3 or higher urinary or rectal toxicities at median follow-up of 10.8 months (range, 6.4-15.7 months).
CONCLUSIONS: With real-time adaptive planning on a magnetic resonance imaging linear accelerator, dose escalation was achieved in most cases with the intended doses without significantly compromising the dose-volume constraints of the surrounding normal tissue structures. These dosimetric findings were associated with an excellent tolerance profile at 12 months and a low incidence of urinary or rectal toxicity.