To be precise

24 June, 2019

The ICR and The Royal Marsden are pioneers in developing new radiotherapy techniques. Recently, we have made great strides in enhancing the imaging of tumours to deliver more targeted radiation. We look at three strands of research that aim to provide more accurate and kinder treatment for patients

 Six months after prostate cancer patient Barry Dolling became the first person in the UK to be treated on the MR Linac, we are now using this pioneering radiotherapy machine to treat a second tumour type. The PERMIT study is evaluating the benefits of using the MR Linac rather than conventional radiotherapy for localised rectal cancer.

The MR Linac combines two technologies – an MR scanner and a linear accelerator – to precisely locate tumours, tailor the shape of X-ray beams in real time and accurately deliver radiation to moving tumours. The locations of tumours and organs can change over time. For example, a tumour in the lung will move up and down as a person breathes, while a tumour in the prostate or rectum may move from day to day, depending on what the patient has eaten or how full their bladder is.

Professor Robert Huddart, Consultant Clinical Oncologist at The Royal Marsden and Reader at the ICR, who is the Principal Investigator of the PERMIT study, says: “We know rectal cancer responds to high-dose radiation but is hard to focus treatment on. It is difficult to see using standard
imaging techniques, and moves and changes shape day to day.

“The groundbreaking precision of the MR Linac will allow us to adapt the treatment each day to better target the rectum so we can safely deliver higher doses of radiation. We hope this will improve the effectiveness of treatment with fewer side effects.”

Enhanced imaging for targeting cervical cancer

Using a combination of imaging techniques while treating gynaecological tumours has been the focus of recent research at The Royal Marsden and the ICR. A multidisciplinary team explored the benefits of combining ultrasound and cone-beam computed tomography (CBCT) – an imaging technique used just before treatment in which the X-rays form a cone shape – in order to target the uterus and cervix with image-guided radiotherapy (IGRT).

Experts – including Dr Emma Harris, Imaging for Radiotherapy Adaptation Team Leader at the ICR, and Consultant Clinical Oncologist Dr Susan Lalondrelle and Lead Research Radiographer Dr Helen McNair of The Royal Marsden and the ICR – compared images from patients using ultrasound and CBCT with those using ultrasound or CBCT alone.

The results will be published in the International Journal of Radiation Oncology, Biology, Physics. Gynaecological cancer patients are normally asked to have a full bladder when having radiotherapy to maintain a consistent target position and reduce the dose to the bowel and bladder. However,
patients’ bladders can’t always fill the same way each day.

“In a patient having standard treatment for cervical cancer in around 25 daily sessions, we would expect the cervix and the uterus to be in a different position each day,” says Dr Harris.

“We wanted to see if ultrasound and CBCT would give enhanced images of the uterus and surrounding soft tissue, allowing us to target the radiation more accurately to minimise damage to healthy tissue. Using ultrasound and CBCT together gave users more confidence about the location of the target.”

Dr Lalondrelle says: “The next step is to bring these exciting technologies together into everyday practice. We will shortly start recruitment on a new clinical trial that further evaluates the real benefit to patients.”

The next step is to bring these exciting technologies together into everyday practice. We will shortly start recruitment on a new clinical trial that further evaluates the real benefit to patients.

Establishing the safety of SBRT

Stereotactic body radiotherapy (SBRT) delivered over a shorter period is as safe as conventionally fractionated radiotherapy in men with low- or intermediate-risk localised prostate cancer, early findings from the international randomised PACE trial show. Principal Investigator Dr Nicholas van As, Medical Director at The Royal Marsden and a Reader at the ICR, presented research from the PACE B arm of the trial at the Genitourinary Cancers Symposium, held in San Francisco in February.

The trial compared patients who received five sessions, or fractions, of SBRT with those who received standard radiotherapy in either 20 or 39 fractions. SBRT treatment resulted in acute genitourinary toxicity rates of 22 per cent, while conventional radiotherapy resulted in rates of 27 per cent. According to Dr van As, these were “very acceptable rates of acute toxicity – lower than we expected – and importantly, [there was] no statistical difference between the SBRT arm and the conventionally fractionated arm”.

PACE B is now closed for recruitment, but PACE A remains open. In this arm, patients who are candidates for surgery will either have a prostatectomy or receive prostate SBRT delivered in five fractions.

Meanwhile, PACE C is due to open to intermediate- or high-risk patients who refuse surgery or are not suitable for it. These patients will receive either 20 fractions of conventional radiotherapy or prostate SBRT in five fractions. “There has been considerable discussion and analysis of the risks versus the benefits of different radiation treatment techniques, especially in patients with low- or intermediate-risk prostate cancer – in large part because the side effects of treatment can affect quality of life,” says Dr van As.

“One of the clinical trial’s goals was to find whether SBRT or a more conventionally fractionated radiotherapy schedule would provide a safer treatment choice. These early trial results are promising and help us to better understand the effect of different radiation therapy techniques on the treatment of prostate cancer. We look forward to analysing additional trial data.”