Ireland’s University Hospital Galway marks 2,000th patient to receive Clarity soft tissue visualization scans for prostate radiotherapy – first of two articles on UHG’s advanced treatment solutions
While many centers rely on the cone-beam CT technology on their linacs for IGRT of soft tissue targets, clinicians at University Hospital Galway (UHG, Galway, Ireland) have satisfied all of their soft tissue imaging needs for prostate treatments with Clarity™ soft tissue visualization. Since 2008, UHG clinicians have used 3D ultrasound-based Clarity on one of the hospital’s three Siemens linacs, each equipped only with an electronic portal imaging device (EPID). In the spring of 2016, a 64-year-old man became UHG’s 2,000th patient to receive Clarity scans for treatment planning and for localizing the prostate just before therapy (see 2,000th UHG Clarity patient heads toward finish line).
“In 2014 there were 209 patients treated for prostate cancer,” says Margaret Moore, UHG’s Head of Radiation Physics. “Of these, 175 were treated using Clarity for daily localization. This represents 84% of the total prostate volume.”
Prostate cancer is the most common cancer in men in the UK, with 41,799 patients diagnosed in 2011.
UHG physicians and therapists make every effort to ensure as many patients as possible are eligible for Clarity scans, as the alternative is using a linac’s EPID and aligning with the pelvic nodes or bony anatomy.
“A colleague here, John French, was researching whether it’s best to use ultrasound and move with prostate motion or look at the EPID and align with the pelvic nodes,” Moore says. “His study showed that you absolutely must move with your main target – alternative views were intricate and involved too big of an error. We know there is prostate movement every day and the only way to accurately treat your target is to follow it. With the EPID you can’t see it.”
Bladder and rectum surveillance
For a successful Clarity scan, radiation therapists at UHG have made a science of enforcing bladder filling requirements and imaging the rectum, the two organs that have the greatest impact on prostate visualization and position (i.e., movement).
A full bladder provides the best acoustic window for an ultrasound scan of the prostate and minimizes the dose the bladder receives during treatment.
“The Clarity patient’s biggest role in treatment is drinking water and they take ownership of that responsibility,” observes Stephen Coyne, Service Manager, Radiation Therapy Department. “They not only have to stay hydrated over the course of their treatment, they also need to fill their bladder before each therapy session to enable the pre-fraction Clarity scan. And they have to maintain this practice through 37 fractions.”
UHG’s participation in the UK’s CHHiP trial* and their ongoing experience have informed the staff’s surveillance of rectal diameter and its impact on prostate radiotherapy. On occasion, the position changes in the prostate and surrounding organs detected by Clarity have been large enough to require CT rescanning and replanning to return to the desired dose distribution.
“It’s not enough to track the target, we need to determine the size and vector of prostate position shifts,” Moore notes. “Although we had been satisfied in tracking prostate position, we realized that that rectal diameter, as a function of rectal fullness, was becoming an issue. Patients would come in for treatment with a rectal diameter of over five centimeters, but we would treat anyway since we could see the prostate with Clarity. Over several treatments, however, bowel activity would begin to normalize for these patients, and of course, once the rectum started shrinking the prostate’s position would drop. We would then find a posterior shift of one to three centimeters, requiring us to rescan and replan the patient.”
“We know there is prostate movement every day and the only way to accurately treat your target is to follow it.”
The impact of rectal diameter prompted department staff to change their work practice for prostate cancer patients, according to Coyne. Now, before planning begins, patients receive a CT “mini-scan” to check rectal diameter. If it exceeds five centimeters, the patient is encouraged to evacuate. Failing that, the physician will prescribe a laxative and reschedule the patient for another mini-scan.
“We are looking at options to ensure rectal consistency,” he says. “The rectum never stays that large and we end up rescanning. Apart from the ability to accurately pin down prostate position with Clarity, successful prostate treatment is also about making the bladder and rectum consistent.”
Exploring Clarity 4D Monitoring with Autoscan
Moore and Coyne are interested in the potential of Clarity 4D Monitoring with Autoscan* for their prostate cancer patients. This solution enables physicians to monitor the motion of the prostate and surrounding tissues and organs – in real time and with sub-millimeter accuracy – during beam delivery. It uses an automated transperineal ultrasound (TPUS) approach to scanning, employing a motorized probe positioned at the patient’s perineum.
“With TPUS, bladder filling requirements can be relaxed to a certain extent,” Moore explains. “Consistent bladder filling is still important, but the patient doesn’t need to be at maximum capacity every day, it can be more comfortable, and this could help even more patients become eligible for Clarity scanning. Secondly, since scanning is automated you’re further reducing variables such as probe placement and scanning technique. Also, monitoring in real time during treatment obviously would enable us to see intra-fraction motion, so if the PTV moved outside the target area you could stop the beam.”
Such a shift could be a consequence of the time it takes to deliver step-and-shoot IMRT, Coyne adds.
“The treatment could take between five and 10 minutes and since the patient has been drinking water his bladder will continue to fill during that period and cause the prostate to move,” he says. “Similarly, the rectum could fill with gas or solid waste – quite quickly in some cases – which we wouldn’t see unless the scanning was real time.”
Coyne adds that he and his colleagues wondered about whether patient compliance would be an issue with the TPUS approach.
“We’ve been talking to other departments that use this product and they didn’t seem to have a problem,” he says. “We think that patient hesitation about TPUS would just go away on its own accord once treatment in underway.”
Both Moore and Coyne are hopeful that with the current progression to adoption of the CHHiP protocol the case for moving from the current Clarity system to Clarity 4D Monitoring with Autoscan will be advanced.
“If patients need only 20 slots on the machine versus 37 and we can treat more patients, then that’s a huge efficiency drive and it’s better for the patients,” Moore says.
*For more information about Clarity soft tissue visualization and Clarity 4D Monitoring, visit www.elekta.com/clarity
- Wilkins A, Mossop H, Syndikus I, et al. Hypofractionated radiotherapy versus conventionally fractionated radiotherapy for patients with intermediate-risk localized prostate cancer: 2-year patient-reported outcomes of the randomized, non-inferiority, phase 3 CHHiP trial. Lancet Oncol 2015; 16:1605-16.
- Kleefeld C, Moore M, van der Putten W. Clinical evaluation of an intra-modality 3D ultrasound IGRT system. World Congress on Medical Physics and Biomedical Engineering, September 7 – 12, 2009, Munich, Germany, Volume 25/1 of the series IFMBE Proceedings pp 488-491.
*CHHiP trial suggests 20 fractions as good as 37 for prostate radiotherapy
University Hospital Galway was the only Clarity center to participate in the 3,163-patient CHHiP1 (Conventional or Hypofractionated High Dose Intensity Modulated Radiotherapy in Prostate Cancer) trial. CHHiP is a randomized, non-inferiority phase 3 trial done in 71 centers, of which 57 UK hospitals took part in a Quality of Life (QoL) substudy.
Men with prostate cancer undergoing radiotherapy were randomly assigned to receive a standard fractionation schedule of 74 Gy in 37 fractions or one of two hypofractionated schedules: 60 Gy in 20 fractions or 57 Gy in 19 fractions. Among the participants, 2,100 consented to be included in the QoL substudy, in which they completed QoL questionnaires at baseline, pre-radiotherapy, 10 weeks post-treatment and six to 24 months post-radiotherapy.1
The results showed that the incidence of patient-reported bowel symptoms was low and similar between patients in the 74 Gy control group and the hypofractionated groups up to 24 months post-radiotherapy. The authors concluded that if efficacy outcomes from CHHiP showed non-inferiority for hypofractionated treatments, “these findings will add to the growing evidence for moderately hypofractionated radiotherapy schedules becoming the standard treatment for localised prostate cancer.”1
UGH was allocated 10 patients for the CHHiP trial.
“Participating centers were required to use IMRT to treat the patients and had to employ a 3D image guidance system,” says UHG’s Head of Radiatherapy Physics, Margaret Moore. “The study coordinators validated our use of Clarity.”
The study results prompted UHG to establish a CHHiP focus group, whose mission is to work toward selecting patients for a hypofractionated (60 Gy/20 fraction) prostate cancer treatment.
“The margins for a 3 Gy fraction also are stricter due to the CHIPP specification of 3 PTV volume levels compared to the 1 PTV volume level specified now. However, with Clarity we can show that we’re hitting our target every day, because we scan every day and can reposition if necessary.”