BIOPROP: Biologically Optimised Prostate Cancer Radiotherapy or Dose Painting
Session type: Poster / e-Poster / Silent Theatre session
Patients with localised prostate cancer have better survival after high dose radiotherapy combined with hormone therapy compared to either treatment alone; however, a significant proportion relapse locally. Further conventional dose escalation may improve biochemical control, but at increased toxicity. We propose BIOPROP, a phase-II trial for intermediate- and poor-risk patients: radiobiologically optimised isotoxic intensity-modulated RT, including dose painting of the dominant interprostatic lesions (DILs). A Feasibility Study Application was recently submitted to CTAAC.
We have implemented Radiobiological optimisation via the Pinnacle TPS Research Interface (PRI). The objective is: maximise Tumour Control Probability (TCP Marsden model ) whilst not exceeding fixed Normal Tissue Complication Probability (NTCP Lyman-Kutcher-Burman model ), for different rectal endpoints - bleeding  and faecal incontinence . All patients receive adjuvant hormone therapy. Randomisation is between:
ARM 1: UK standard intensity-modulated (IM) treatment uniform 74 Gy to the PTV in 37 fractions.
ARM 2: IM plan created with the above biological objective plus the physical objectives of maximum 84 Gy in the PTV but only 74 Gy to the urethra.
ARM 3: DILs are identified from template biopsies and diffusion-weighted MRI with higher clonogen density being assigned. The biological and physical objectives are as for Arm 2.
Six CHHIP  patients have been re-planned according to the above criteria. The average TCP in Arm 1 is 71.8% . In Arm 2, the escalated dose distributions in the PTV yield 74.9% and 75.2% for ?/? = 10, 3 respectively, for negligible changes in NTCP.
In Arm 3 mean TCPs are 79.7% and 80.8% respectively, also for negligible toxicity change.
As a feasibility test, one patient has been treated according to Arm 3.
Radiobiologically-guided dose painting is expected to yield significant TCP gains. Treatments will be delivered with rotational IMRT (RapidArc, SmartArc, VMAT, Tomotherapy) ensuring maximum conformality.