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Quality improvements in radiation oncology clinical trials

Clinical trials have become the primary mechanism to validate process improvements in oncology clinical practice. Over the past two decades there have been considerable process improvements in the practice of radiation oncology within the structure of a modern department using advanced technology for patient care. Treatment planning is accomplished with volume definition including fusion of multiple series of diagnostic images into volumetric planning studies to optimize the definition of tumor and define the relationship of tumor to normal tissue. Daily treatment is validated by multiple tools of image guidance. Computer planning has been optimized and supported by the increasing use of artificial intelligence in treatment planning. Informatics technology has improved, and departments have become geographically transparent integrated through informatics bridges creating an economy of scale for the planning and execution of advanced technology radiation therapy. This serves to provide consistency in department habits and improve quality of patient care. Improvements in normal tissue sparing have further improved tolerance of treatment and allowed radiation oncologists to increase both daily and total dose to target. Radiation oncologists need to define a priori dose volume constraints to normal tissue as well as define how image guidance will be applied to each radiation treatment. These process improvements have enhanced the utility of radiation therapy in patient care and have made radiation therapy an attractive option for care in multiple primary disease settings. In this chapter we review how these changes have been applied to clinical practice and incorporated into clinical trials. We will discuss how the changes in clinical practice have improved the quality of clinical trials in radiation therapy. We will also identify what gaps remain and need to be addressed to offer further improvements in radiation oncology clinical trials and patient care.

Credentialing results from IMRT irradiations of an anthropomorphic head and neck phantom

PURPOSE

This study was performed to report and analyze the results of the Radiological Physics Center's head and neck intensity-modulated radiation therapy (IMRT) phantom irradiations done by institutions seeking to be credentialed for participation in clinical trials using intensity modulated radiation therapy.

METHODS

The Radiological Physics Center's anthropomorphic head and neck phantom was sent to institutions seeking to participate in multi-institutional clinical trials. The phantom contained two planning target volume (PTV) structures and an organ at risk (OAR). Thermoluminescent dosimeters (TLD) and film dosimeters were imbedded in the PTV. Institutions were asked to image, plan, and treat the phantom as they would treat a patient. The treatment plan should cover at least 95% of the primary PTV with 6.6 Gy and at least 95% of the secondary PTV with 5.4 Gy. The plan should limit the dose to the OAR to less than 4.5 Gy. The passing criteria were ±7% for the TLD in the PTVs and a distance to agreement of 4 mm in the high dose gradient area between the PTV and the OAR. Pass rates for different delivery types, treatment planning systems (TPS), linear accelerators, and linear accelerator-planning system combinations were compared.

RESULTS

The phantom was irradiated 1139 times by 763 institutions from 2001 through 2011. 929 (81.6%) of the irradiations passed the criteria. 156 (13.7%) irradiations failed only the TLD criteria, 21 (1.8%) failed only the film criteria, and 33 (2.9%) failed both sets of criteria. Only 69% of the irradiations passed a narrowed TLD criterion of ±5%. Varian-Elipse and TomoTherapy-HiArt combinations had the highest pass rates, ranging from 90% to 93%. Varian-Pinnacle(3), Varian-XiO, Siemens-Pinnacle(3), and Elekta-Pinnacle(3) combinations had pass rates that ranged from 66% to 81%.

CONCLUSIONS

The head and neck phantom is a useful credentialing tool for multi-institutional IMRT clinical trials. The most commonly represented linear accelerator-planning system combinations can all pass the phantom, though some combinations had higher passing percentages than others. Tightening the criteria would significantly reduce the number of institutions passing the credentialing criteria. Causes for failures include incorrect data entered into the TPS, inexact beam modeling, and software and hardware failures.

Development of a novel treatment planning test for credentialing rotational intensity-modulated radiotherapy techniques in the UK

OBJECTIVE

The increasing use of tomotherapy and volumetric-modulated arc therapy in UK centres will result in more centres choosing to use this technology in a clinical trial setting. The Radiotherapy Trials Quality Assurance (RTTQA) group has developed a new procedure to integrate into the UK intensity-modulated radiotherapy (IMRT) credentialing programme to cover rotational IMRT delivery techniques.

METHODS

A planning test [three-dimensional treatment planning system (3DTPS)] was designed specifically for rotational IMRT techniques. The feasibility of using this test in the credentialing programme for rotational IMRT was validated by 10 experienced UK centres. The study included five centres using Varian RapidArc™ (RA) (Varian Medical Systems, Milpitas, CA), two using Elekta VMAT™ (VMAT) (Elekta Inc., Norcross, GA) and three using helical tomotherapy (HT) plans. Centres were asked to carry out their own in-house quality assurance (QA) for the plans submitted for this study. A survey was sent out to centres aiming to gather information on their experience in undertaking the exercise and their QA results.

RESULTS

All centres fulfilled the primary goal by achieving the dose constraints of the primary planning target volume and organ at risk. Seven centres (three RA, one VMAT and three HT plans) were able to fulfil the secondary goal. Among those seven centres, three centres (two RA and one VMAT plans) achieved the tertiary goal. The results of the survey indicated that the 3DTPS test is a clinically relevant and practical planning test to be used.

CONCLUSION

A planning test for rotational therapy techniques was developed for the RTTQA IMRT credentialing programme.

ADVANCES IN KNOWLEDGE

This study validated the feasibility of a 3DTPS test to be used as part of a credentialing programme for rotational IMRT techniques in the UK.

Pre-trial quality assurance processes for an intensity-modulated radiation therapy (IMRT) trial: PARSPORT, a UK multicentre Phase III trial comparing conventional radiotherapy and parotid-sparing IMRT for locally advanced head and neck cancer

The purpose of this study was to compare conventional radiotherapy with parotid gland-sparing intensity-modulated radiation therapy (IMRT) using the PARSPORT trial. The validity of such a trial depends on the radiotherapy planning and delivery meeting a defined standard across all centres. At the outset, many of the centres had little or no experience of delivering IMRT; therefore, quality assurance processes were devised to ensure consistency and standardisation of all processes for comparison within the trial. The pre-trial quality assurance (QA) programme and results are described. Each centre undertook exercises in target volume definition and treatment planning, completed a resource questionnaire and produced a process document. Additionally, the QA team visited each participating centre. Each exercise had to be accepted before patients could be recruited into the trial. 10 centres successfully completed the quality assurance exercises. A range of treatment planning systems, linear accelerators and delivery methods were used for the planning exercises, and all the plans created reached the standard required for participation in this multicentre trial. All 10 participating centres achieved implementation of a comprehensive and robust IMRT programme for treatment of head and neck cancer.

Challenges in credentialing institutions and participants in advanced technology multi-institutional clinical trials

The Radiological Physics Center (RPC) has functioned continuously for 38 years to assure the National Cancer Institute and the cooperative groups that institutions participating in multi-institutional trials can be expected to deliver radiation treatments that are clinically comparable to those delivered by other institutions in the cooperative groups. To accomplish this, the RPC monitors the machine output, the dosimetry data used by the institutions, the calculation algorithms used for treatment planning, and the institutions' quality control procedures. The methods of monitoring include on-site dosimetry review by an RPC physicist and a variety of remote audit tools. The introduction of advanced technology clinical trials has prompted several study groups to require participating institutions and personnel to become credentialed, to ensure their familiarity and capability with techniques such as three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, stereotactic body radiotherapy, and brachytherapy. The RPC conducts a variety of credentialing activities, beginning with questionnaires to evaluate an institution's understanding of the protocol and their capabilities. Treatment-planning benchmarks are used to allow the institution to demonstrate their planning ability and to facilitate a review of the accuracy of treatment-planning systems under relevant conditions. The RPC also provides mailable anthropomorphic phantoms to verify tumor dose delivery for special treatment techniques. While conducting these reviews, the RPC has amassed a large amount of data describing the dosimetry at participating institutions. Representative data from the monitoring programs are discussed, and examples are presented of specific instances in which the RPC contributed to the discovery and resolution of dosimetry errors.

Dose specification and quality assurance of radiation therapy oncology group protocol 95-17; a cooperative group study of iridium-192 breast implants as sole therapy

PURPOSE

The Radiation Therapy Oncology Group (RTOG) protocol 95-17 was a Phase I/II trial to evaluate multicatheter brachytherapy as the sole method of adjuvant breast radiotherapy for Stage I/II breast carcinoma after breast-conserving surgery. Low- or high-dose-rate sources were allowed. Dose prescription and treatment evaluation were based on recommendations in the International Commission on Radiation Units and Measurements (ICRU), Report 58 and included the parameters mean central dose (MCD), average peripheral dose, dose homogeneity index (DHI), and the dimensions of the low- and high-dose regions.

METHODS AND MATERIALS

Three levels of quality assurance were implemented: (1) credentialing of institutions was required before entering patients into the study; (2) rapid review of each treatment plan was conducted before treatment; and (3) retrospective review was performed by the Radiological Physics Center in conjunction with the study chairman and RTOG dosimetry staff.

RESULTS

Credentialing focused on the accuracy of dose calculation algorithm and compliance with protocol guidelines. Rapid review was designed to identify and correct deviations from the protocol before treatment. The retrospective review involved recalculation of dosimetry parameters and review of dose distributions to evaluate the treatment. Specifying both central and peripheral doses resulted in uniform dose distributions, with a mean dose homogeneity index of 0.83 +/- 0.06.

CONCLUSIONS

Vigorous quality assurance resulted in a high-quality study with few deviations; only 4 of 100 patients were judged as representing minor variations from protocol, and no patient was judged as representing major deviation. This study should be considered a model for quality assurance of future trials.