Session Item

To investigate treatment outcomes and compliance in patients with organ-confined prostate cancer treated with dose-intensified Linac-based SBRT using a novel electromagnetic transmitter-based tracking system to account for intra-fractional organ motion

Thirteen patients with intermediate unfavorable (70%) and selected high-risk prostate cancer (30%) underwent dose-escalated SBRT in 4 or 5 fractions (BED 1.5 = 279 Gy and 253 Gy, respectively). ADT was prescribed concomitantly, as per standard of care. The VMAT treatment consisted in two 6FFF or 10FFF arcs optimized to have the 95% isodose covering at least 95% of the PTV (2 mm isotropic expansion of the CTV). The beam delivery was interrupted whenever the real time tracking registered a displacement that exceeded 2 mm to promptly correct the prostate motion. The incidence of treatment-related genitourinary (GU) and gastrointestinal (GI) toxicity, patient QOL, and IPSS scores were computed from the start of treatment to the last follow-up date.

All patients (median age 77 years) completed the treatment in the expected time and their compliance to the procedure was excellent. At a median follow up 6 months, only one patient developed a G2 acute rectal toxicity. No other acute nor late Grade 2 or higher GI (rectal) and GU side effects were observed. EPIC-26 scores in the urinary domain decreased from a median baseline of 86 pre-treatment to 79 at one-month, and returned to baseline at a later timepoint (median score of 85 at 6 months). The same features for EPIC-26 scores in the bowel domains were 92, 80 and 91, respectively. The median IPSS increased from 8 at baseline to 12 one-month after treatment, and settled to 6 thereafter.

Our preliminary findings show that Linac-based Dose-intensified SBRT for unfavorable prostate tumors does not come at the cost of an increased toxicity, provided that a reliable technique for real time prostate monitoring is ensured. These observations need to be confirmed on a larger scale and a longer follow up.