The SPARK trial is testing the use of Kilovoltage Intrafraction Monitoring in prostate cancer patients being treated with Stereotactic Prostate Adaptive Radiotherapy. The researchers expect this trial to result in better targeted prostate cancer patient outcomes with lower toxicity. The potential application of Kilovoltage Intrafraction Monitoring to other tumour sites will pave the way for additional trials with Australasian radiation oncology leading the world.

Most linear accelerators used to treat cancer patients today are equipped with fixed X-ray imagers which are typically used to take images of a tumour before a patient receives radiotherapy. A new technology, known as Kilovoltage Intrafraction Monitoring has recently emerged which allows images of a tumour to be taken in real-time while the treatment is occurring. The advantage of Kilovoltage Intrafraction Monitoring is that it enables strategies such as patient shifting or beam shifting during treatment which could potentially improve the accuracy of the treatment and reduce the patient's side effects. In addition, due to the accuracy of Kilovoltage Intrafraction Monitoring in targeting tumours, the number of treatment sessions this group of patients will require will be reduced to five as opposed to the 40 sessions required using more conventional treatment methods.

Inclusion Criteria:

1. Histologically proven prostate adenocarcinoma

2. Low or intermediate risk disease as defined by:

   • Low Risk: All of PSA<10 ng/mL, Gleason Grade 6 AND Stage T1 or T2a
   • Intermediate Risk: Any or all of PSA 10-20 ng/mL, Gleason Grade 7 OR Stage T2b-c
   • Absence of high risk features (PSA>20, T3-4, N1 or M1 disease, Gleason score 8-10) (PSA must be within 3 months prior to enrolment)

3. ECOG Performance status 0-2

4. Suitable for definitive external beam radiotherapy (IMRT or VMAT)

5. Ability to have three gold fiducial markers placed in the prostate

6. Six month course of androgen deprivation therapy allowed at clinician discretion.

7. Available for follow up for a minimum of 2 years (up to 3 years)

Exclusion Criteria:

1. Lymph node irradiation
2. Any other systemic anti-prostate cancer therapy (i.e. non-ADT) both proven in the metastatic setting and investigational (e.g. docetaxel, enzalutamide)
3. Artificial hip(s) (Unable to visualise markers through prosthesis)
4. Prostate volume > 90 cm3 measured from the CT scan
5. Patient lateral dimension >40cm as measured at the level of the prostate from the CT scan
6. Suboptimal fiducial markers placement for treatment utilising KIM as assessed by a medical physicist by measuring marker positions from the CT scan
7. Fiducial migration or fewer than 3 fiducials present in the CT scan