Online Adaptive Stereotactic Body Radiotherapy for Localized Prostate Cancer (X-SMILE)

Inclusion Criteria:

• histologically confirmed localized prostate cancer

• planned treatment is SBRT according to standard of care and consists of definitiveCT or MRI online adaptive SBRT of the prostate according to the PACE trial whichincludes a total dose to clinical target volume 1 (CTV1, i.e. prostate and proximal 1 cm of the seminal vesicle) of 40.0 Gy in 5 weekly fractions (single dose of 8.0Gy) and total dose to planning target volume 1 (PTV1) of 37.5 Gy in 5 weeklyfractions (single dose of 7.5 Gy) with a compromise for bowel sparing allowed. Forpatients with unfavorable intermediate to very high-risk disease (according to NCCNguidelines) a total dose to the planning target volume 2 (PTV2, i.e. proximal 1-2 cmof the seminal vesicle) of 32.5 Gy in 5 weekly fractions (single dose of 6.5 Gy)will be delivered.

• intermediate to (very) high risk localized prostate cancer (≤ cT3a and Gleason score ≤ 9 and/or PSA ≤ 20 ng/ml)

• prostate volume > 60 cc and/or IPSS > 12;

Exclusion Criteria:

• Very high risk localized prostate cancer with indication for ADT and ARPI (i.e.Gleason ≥ 8 and cT3a)

• Involvement of seminal vesicles (cT3b)

• Contraindications against definitive CT or MRI-adaptive radiotherapy of theprostate, e.g. inflammatory bowel disease (IBD); previous radiotherapy in thepelvis, previous local radiotherapy of the prostate, contraindication for MRI or CT;

• Patients with severe genitourinary symptoms (e.g. recent urinary retention ≥ grade 3according CTCAE v.5.0);

• Lymph node metastases or distant metastases (i.e. no localised prostate cancer);

• Participation in a clinical trial which might influence the results of this project.