Author: Awens Alphonse, Nebi Demez, Michael Kasper, Noufal Manthala Padannayil, Shyam Pokharel, Suresh Rana, Lauren A. Rigsby, Tino Romaguera, Hina Saeed, Nishan Shrestha, Somol Sunny 👨🔬
Affiliation: Lynn Cancer Institute, Boca Raton Regional Hospital, Baptist Health South Florida 🌍
Purpose: Prostate stereotactic body radiation therapy (SBRT) requires precise dose delivery to the target volume and organ-at-risk (OAR) sparing. This study compares MR-Linac (MRL) and CyberKnife (CK), two advanced radiotherapy modalities, to evaluate their dosimetric outcomes and treatment efficiencies.
Methods: Five prostate cancer patients previously treated with MRL were retrospectively analyzed. CT scans and structure sets were transferred to the CK treatment planning system (TPS). Target volumes excluded OARs (rectum, bladder, and urethra). Treatment plans delivered 40 Gy over 5 fractions, optimized to meet institutional clinical goals. Dosimetric parameters, including conformity index, gradient index, target coverage, and OAR sparing, were compared. Treatment times (beam-on) were estimated by each TPS.
Results: Both modalities achieved >95% target coverage with prescribed doses of 40 Gy, 36.25 Gy, and 38 Gy for prostate, PTV, and seminal vesicles, respectively. The conformity index was similar for both systems (0.96 ± 0.01 for MRL vs 0.98 ± 0.04 for CK). CK demonstrated a better gradient index (3.83±0.75 vs. 4.60±0.46). Both systems delivered comparable OAR sparing, successfully meeting clinical goals. On average, estimated treatment times were shorter with MRL (9.18 ± 1.05 minutes) compared to CK (20.6 ± 2.25 minutes).
Conclusion: MRL and CK demonstrated comparable dosimetric outcomes for prostate SBRT, with each offering unique strengths. CK’s superior gradient index highlights its capacity for precise dose fall-off, while MRL provides significant treatment efficiency as well as superior integrated imaging, with the added advantage of an adaptive workflow. These findings emphasize the complementary capabilities of both systems, allowing clinicians to tailor treatment approaches based on individual patient needs and clinical priorities.