Proton Therapy Congress 2016

Clinical trials investigating proton therapy for other indications 

Prof Nancy Mendenhall - University of Florida, Gainesville, USA

My talk will be focussed on the outcomes that we’ve seen at the University of Florida. We have treated over 6,500 patients, 98% of them have been on either a prospective outcome tracking study or in a clinical trial and the experiences are mature enough and large enough in three areas. These include prostate cancer, paediatric tumours and tumours in a difficult head and neck site – sinus tumours. I think we have enough data to prove principles of proton therapy, principles that either show that when you reduce integral dose you will have fewer side effects and a better quality of life or you can escalate or intensify the radiation dose to the target and get a better cure rate. In some cases because there is so much less dose to normal tissues you can safely compress a treatment, hyperfractionate it.

How have these treatments affected patients?
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In prostate cancer it appears to us that the disease control rates are 10-15% higher with proton therapy than they are with conventional radiation. In addition it appears to us that the rate of bowel dysfunction, specifically frequency and urgency, major issues for men who have received radiation, the rates of those being bothersome are about half with proton therapy what they are with conventional radiation. We’ve also learned that we can achieve the same outcomes with proton therapy delivered in shorter courses, a 5½ week regimen compared to an 8 week regimen in selected patients. Interestingly, it appears that the toxicity goes up quite a bit when you try to do this kind of a course with conventional radiation. Our NRG or RTOG major co-operative study group in the US just published an outcome of a randomisation between the same hyperfractionated course and standard radiation and their toxicity rate went up substantially when they tried to decrease the number of treatments. So we think that this is particularly important in prostate cancer because it will reduce the cost of treatment substantially.

In the sinus tumours we’ve treated a large number of them and it appears that we’ve got disease control in a very, very high proportion of these really difficult tumours. These tumours sit near the optic apparatus so we are always worried about blindness because of either radiation damage to the optic nerves, the and more the retina. Our rate of blindness is extremely low compared to historical studies with conventional radiation and our disease control rate is extremely high. When we look at the doses that we’ve been able to give to the target they appear to be substantially higher than what can be achieved with conventional radiation which probably accounts for the higher disease control rate.

In children, while we’ve treated a lot of children with different kinds of malignancies, my talk focussed on children who have come to us specifically from the UK. This is data that was compiled by one of my colleagues and what it shows is really high disease control rates in three of the most common paediatric brain tumours in these children coming 4,000 miles to Florida for treatment from the UK.

Any final thoughts?

This has been a wonderful conference, I’ve thoroughly enjoyed the broad range of speakers. We’ve had biologists, we’ve had physicists, clinicians, engineers, it’s been wonderful.