In radiation therapy, patient safety starts and ends with independent QA, a comprehensive programme of machine, patient-specific and workflow checks for identifying – and mitigating – human and system errors in an expanding universe of complex treatment variables. By putting a forensic focus on the quality and accuracy of treatment planning, delivery and management, independent QA gives the radiation oncology team confidence that treatment is being delivered to the tumour site as intended while minimizing collateral damage to healthy tissues and organs at risk (OARs).

Here, Physics World talks to Jeff Kapatoes, senior director for regulatory and research at Sun Nuclear Corporation, a US-based manufacturer of QA solutions for radiotherapy and diagnostic imaging providers, about the enduring – indeed growing – importance of independent QA for patient safety, continuous improvement and clinical innovation in the radiation oncology workflow.

Why is independent QA fundamental to the successful delivery of radiotherapy treatments?

Independent QA provides an essential audit of the evolving radiotherapy delivery system, complementing the integrated “self-checks” on the treatment machine. There will always be residual risk from unforeseen failure modes in today’s complex treatment systems – a risk that is best addressed through independent QA to avoid any conflict of interest. Put simply: QA that is not independent is a self-check, and self-checking is inherently biased and driven by familiarity contamination or “group think” – both in design and risk assessment.

What’s more, as radiotherapy systems become more interoperable – knitting together hardware and software subsystems from multiple vendors – the likelihood of testing and verifying every configuration as part of a comprehensive self-check becomes ever-more remote. The bottom line: independent QA not only maintains the desired quality of treatment delivery, it drives continuous improvement in patient safety by rooting out systematic errors and simultaneously highlighting opportunities for machine/workflow optimization.

So independent QA and continuous improvement go hand-in-hand?

Correct – though that improvement proceeds along a couple of distinct coordinates. Upstream patient safety, for example, is shaped by the quality of the core radiotherapy technology.

Progress has been rapid in this regard over the past decade, with wide-scale deployment of advanced modalities – including MR-guided radiotherapy (MR/RT), stereotactic radiosurgery/stereotactic body radiotherapy (SRS/SBRT) and volumetric modulated-arc therapy (VMAT) – all of which enhance treatment delivery and dose distribution accuracy when implemented correctly.

Meanwhile, independent QA (or downstream patient safety) is shaped by our ability to monitor and improve the quality of radiotherapy treatments. In other words: to ensure that the treatment system is delivering radiation to the patient as intended. Here too, capabilities are progressing dramatically, with once abstract concepts such as anatomical dose verification and in vivo monitoring becoming routinely available, improving our ability to detect myriad intra- and interfraction patient and machine errors.

In what ways do independent QA vendors like Sun Nuclear and its peers benefit the medical physics team?

Sun Nuclear’s QA solutions are used in many ways to deliver enhanced treatment outcomes and improved operational efficiencies in the radiation oncology clinic. That could mean commissioning a new treatment machine or clinical workflow; daily, weekly or monthly machine QA checks; as well as all aspects of patient-specific QA. In short, we give medical physicists the QA tools they need to do their job better as the independent auditors of radiation treatment and patient safety.

As such, Sun Nuclear is part of the collective QA conversation with the medical physics community, whether that’s requirements-gathering at scale for our product development roadmap or collaborating with clinical scientists directly on advanced QA technologies. It’s also worth noting how a dynamic and innovative QA ecosystem supports the commercial objectives of the radiotherapy equipment manufacturers, providing them with independent insurance and security regarding the safety of their treatment systems in the clinic.

What role does independent QA play in early-stage R&D and clinical translation of next-generation radiotherapy technologies?

QA tools from Sun Nuclear and other product vendors are fundamental for successful technology innovation and clinical translation of advanced radiotherapy modalities. The commercial introduction of the Elekta Unity MR-linac is a case in point. Back in 2012, Sun Nuclear supported the early-stage clinical evaluation of this pioneering MR/RT breakthrough, providing an MR-compatible ArcCHECK (a 4D diode array for patient QA) to Elekta’s university research partner UMC Utrecht in the Netherlands.

Right now, we have around a dozen academic partners and university research hospitals using our products for preclinical research on novel treatment delivery systems. At the same time, established radiotherapy system manufacturers, as well as new-entrant technology start-ups, commonly deploy a suite of our QA solutions across the organization to support product development, manufacturing and their installation and service teams.

Lapaz MR 2

Easing adoption: with the aid of Sun Nuclear's proven ArcCHECK-MR and IC PROFILER-MR solutions, Madrid's Hospital Universitario La Paz recently completed installation of a new Elekta Unity MR-linac. (Photo courtesy of Hospital Universitario La Paz)

Do you see any threats to the culture of best practice and continuous improvement regarding patient safety in radiotherapy?

As one of several companies focused exclusively on independent QA, we see various structural “issues arising” that give cause for concern – and pause for thought. For starters, there’s a concerted move by radiotherapy equipment makers to integrate more and more downstream patient safety checks into their delivery systems. While there are operational benefits for sure, self-checking on its own is not enough and should not be a replacement for a rigorous, independent QA programme. Today’s radiotherapy systems are so complex that it is simply not possible to mitigate every potential risk internally – hence the need for independent evaluation and verification as a default setting.

There are also concerns around data – especially open access to the data generated by the treatment planning system, the linac (machine log files) and electronic portal imaging device (EPID) during treatment. While there have already been attempts to restrict access and monetize this data, it’s worth restating that the data is “owned” by the clinic and must remain freely accessible to enable independent analysis of radiotherapy fulfilment. A research study presented at the ESTRO 2020 Meeting by Iridium Kankernetwerk, Belgium, is instructive in this regard, with independent downstream QA – predicated on full data access at a single clinic over the course of two years – identifying 4000 actionable errors and opportunities for improvement within 56,000 delivered fractions. Just one example among many of the role that independent QA plays in the detection of random and systemic errors, the prevention of future errors, and the identification of opportunities for improved treatment delivery.

Where next for independent QA?

The independent QA community is in robust health. In fact, two of our more recent innovations – the SunCHECK platform (for integrated machine and patient QA) and SRS MapCHECK (a high-density diode array for SRS patient QA) – have seen tremendous clinical uptake because of the efficiency gains they provide when embedded in the treatment workflow. Proof-positive of the enduring demand for independent QA solutions – even with the blurring of boundaries that follows from more integrated self-check features being rolled out by the radiotherapy equipment vendors.

The competition is welcome in any case and will only accelerate product innovation and the introduction of enhanced QA solutions for medical physicists and the cross-disciplinary radiation oncology team. Right now, for example, there are exciting opportunities taking shape around automation, integration and machine learning within current treatment modalities. Longer term, innovative QA products and services will also be needed to support the clinical translation of next-generation treatment technologies such as FLASH radiotherapy and biological IGRT.