Association between radiotherapy protocol variations and outcome in the CONVERT trial

Background

Radiotherapy quality assurance (QA) is integral to radiotherapy delivery. Here we report comprehensive contouring, dosimetry, and treatment delivery QA, describe protocol compliance, and detail the impact of protocol variations on acute grade ≥3 toxicity, progression free survival (PFS), and overall survival (OS) in the phase III CONVERT trial.

Materials/Methods

Radiotherapy planning data from one hundred randomly selected patients were requested. Members of the CONVERT Trial Management Group (TMG) recontoured the heart, lung, and spinal cord organs at risk (OAR) according to the trial guideline. The existing radiotherapy plan were re-applied to the new structures and the new dosimetric data were recollected. Compliance with radiotherapy QA components were recorded and radiotherapy QA components were pooled into protocol variations: acceptable, acceptable variation, and unacceptable variation. Univariable analysis with a Cox proportional hazards model established the relationship between protocol variations and patient outcome.

Results

Ninety-three cases were submitted for retrospective radiotherapy QA review. Demographics of the radiotherapy QA cohort (n=93) matched the non-QA (n=450) cohort. 97.8% of gross tumour volume (GTV) contours were protocol compliant. OAR contours were non-compliant in 79.6% instances of the heart, 37.6% lung, and 75.3% spinal cord. Of the non-compliant heart contours, 86.5% and 2.7% had contours caudal and cranial to the protocol-defined heart borders. 10.8% did not include the pericardial sac and 2.7% did not include the anterior aspect of the pericardium. Eleven (11.8%) submissions exceeded protocol-defined dosimetric heart constraints; six of which were only noted on the application of protocol-compliant contours. Unacceptable variations were not associated with an increase in grade 3 toxicity (p=0.808), PFS (p=0.232), or OS (p=0.743).

Conclusion

Non-protocol compliant heart contours were associated with increased dose delivered to the heart OAR, with 11.8 % of submitted heart structures exceeding protocol-defined constraints. In this QA cohort of patients with small cell lung cancer, unacceptable variations were not associated with acute grade ≥3 toxicity, PFS, or OS. Radiotherapy QA remains the cornerstone of high-quality radiotherapy delivery and should be embedded into clinical trial and non-clinical trial practice; clinical trials should report standardised radiotherapy QA parameters alongside trial outcomes.

Risk factors for urethral stricture following external beam radiotherapy and HDR brachytherapy for prostate cancer

PURPOSE

A potential late side effect of high-dose-rate (HDR) prostate brachytherapy combined with external beam radiotherapy (EBRT) is urethral stricture. The purpose of this study was to evaluate dosimetric parameters possibly contributing to stricture development, including dose to bladder base and D2cc(Gy) within 10 mm of prostatic urethra (D2cc _10 mm), which has, so far, not been reported in the literature.

METHODS AND MATERIALS

Patients developing urethral stricture, and matched controls, were identified from a prospective database of those receiving 46 Gy in 23 fractions of EBRT, followed by a single 15 Gy HDR brachytherapy dose. Patients had locally advanced, high- and intermediate-risk prostate cancer. Brachytherapy treatment planning parameters (planning target volume (PTV) size (cm ³), V110(%) _{bladder base}, D2cc _10mm, number of HDR catheters, number of source dwell positions, and total source dwell time within 10 mm of the prostatic urethra) were analyzed to determine potential risk factors for urethral stricture.

RESULTS

Seventy-two patients were treated, 22 of whom developed a urethral stricture. Univariate logistic regression performed on the planning parameters identified increased PTV size and D2cc _10 mm, with decreased V110(%) _{bladder base} as risk factors for stricture formation.

CONCLUSIONS

It is suggested that PTV size, V110(%) _{bladder base}, and D2cc _10mm are predictive of urethral stricture formation following EBRT and brachytherapy to the prostate. This study demonstrates the importance of minimizing high dwell times and hot spots close to organs at risk and also the correction of any craniocaudal movement of catheters to avoid potential hot spots in the bulbomembranous urethra where there may be increased dose sensitivity.

Effect of accurate heart delineation on cardiac dose during the CONVERT trial

OBJECTIVE

This study investigated the effect of deviation from protocol in heart delineation for the Concurrent Once-daily Versus twice-daily Radiotherapy (CONVERT) Trial ( ClinicalTrials.gov Identifier NCT00433563) quality assurance (QA) programme and the effect of that on mean cardiac dose and percentage of heart volume receiving ≥5 Gy (V5%) and percentage of heart volume receiving ≥30 Gy (V30%).

METHODS

Patients with limited-stage small-cell lung cancer in the CONVERT trial were randomized to receive 45 Gy in 30# twice daily or 66 Gy in 33# once daily radiotherapy, with concurrent chemotherapy in both arms. Of the 100 trial patient cases reviewed by the QA team [for patient selection, disease/organs at risk (OARs) outlining and treatment planning], 50 patient cases were selected, and the heart was reoutlined according to the "gold standard" trial protocol. Dose-volume histogram (DVH) data were extracted. The impact of change in heart volume on cardiac DVH is presented.

RESULTS

For gold standard cardiac outlines, an increase in V5% and V30% was seen in 77.3% and 81.8% of cases, respectively, in the control arm (45 Gy) and in 78.6% and 82.1% of cases, respectively, in the experimental arm (66 Gy). The median increase in V5% was 1.4% and in V30%, it was 3.4%. The average of the mean cardiac dose for the control arm increased by 2.1 Gy (from 15.2 Gy for the centres outline to 17.3 Gy for the gold standard outline) and for the experimental arm by 2.4 Gy (from 16.2 to 18.6 Gy).

CONCLUSION

This study demonstrates the importance of having a robust QA programme in place to ensure accuracy of cardiac delineation to facilitate future studies investigating the impact of cardiac dose on toxicity. Advances in knowledge: This study highlights the importance of ensuring accurate delineation of OARs in clinical trials, where conclusions about normal tissue toxicity are to be drawn.

Protocol for the isotoxic intensity modulated radiotherapy (IMRT) in stage III non-small cell lung cancer (NSCLC): a feasibility study

INTRODUCTION

The majority of stage III patients with non-small cell lung cancer (NSCLC) are unsuitable for concurrent chemoradiotherapy, the non-surgical gold standard of care. As the alternative treatment options of sequential chemoradiotherapy and radiotherapy alone are associated with high local failure rates, various intensification strategies have been employed. There is evidence to suggest that altered fractionation using hyperfractionation, acceleration, dose escalation, and individualisation may be of benefit. The MAASTRO group have pioneered the concept of 'isotoxic' radiotherapy allowing for individualised dose escalation using hyperfractionated accelerated radiotherapy based on predefined normal tissue constraints. This study aims to evaluate whether delivering isotoxic radiotherapy using intensity modulated radiotherapy (IMRT) is achievable.

METHODS AND ANALYSIS

Isotoxic IMRT is a multicentre feasibility study. From June 2014, a total of 35 patients from 7 UK centres, with a proven histological or cytological diagnosis of inoperable NSCLC, unsuitable for concurrent chemoradiotherapy will be recruited. A minimum of 2 cycles of induction chemotherapy is mandated before starting isotoxic radiotherapy. The dose of radiation will be increased until one or more of the organs at risk tolerance or the maximum dose of 79.2 Gy is reached. The primary end point is feasibility, with accrual rates, local control and overall survival our secondary end points. Patients will be followed up for 5 years.

ETHICS AND DISSEMINATION

The study has received ethical approval (REC reference: 13/NW/0480) from the National Research Ethics Service (NRES) Committee North West-Greater Manchester South. The trial is conducted in accordance with the Declaration of Helsinki and Good Clinical Practice (GCP). The trial results will be published in a peer-reviewed journal and presented internationally.

TRIAL REGISTRATION NUMBER

NCT01836692; Pre-results.

Protocol for the CONVERT trial-Concurrent ONce-daily VErsus twice-daily RadioTherapy: an international 2-arm randomised controlled trial of concurrent chemoradiotherapy comparing twice-daily and once-daily radiotherapy schedules in patients with limited stage small cell lung cancer (LS-SCLC) and good performance status

INTRODUCTION

Concurrent ONce-daily VErsus twice-daily RadioTherapy (CONVERT) is the only multicentre, international, randomised, phase III trial open in Europe and Canada looking at optimisation of chemoradiotherapy (RT) in limited stage small cell lung cancer (LS-SCLC). Following on from the Turrisi trial of once-daily versus twice-daily (BD) concurrent chemoradiotherapy, there is a real need for a new phase III trial using modern conformal RT techniques and investigating higher once-daily radiation dose. This trial has the potential to define a new standard chemo-RT regimen for patients with LS-SCLC and good performance status.

METHODS AND ANALYSIS

447 patients with histologically or cytologically proven diagnosis of SCLC were recruited from 74 centres in eight countries between 2008 and 2013. Patients were randomised to receive either concurrent twice-daily RT(45 Gy in 30 twice-daily fractions over 3 weeks) or concurrent once-daily RT(66 Gy in 33 once-daily fractions over 6.5 weeks) both starting on day 22 of cycle 1. Patients are followed up until death. The primary end point of the study is overall survival and secondary end points include local progression-free survival, metastasis-free survival, acute and late toxicity based on the Common Terminology Criteria for Adverse Events V.3.0, chemotherapy and RTdose intensity.

ETHICS AND DISSEMINATION

The trial received ethical approval from NRES Committee North West-Greater Manchester Central (07/H1008/229). There is a trial steering committee, including independent members and an independent data monitoring committee. Results will be published in a peer-reviewed journal and presented at international conferences.

TRIAL REGISTRATION NUMBER

ISRCTN91927162; Pre-results.

Is pre-trial quality assurance necessary? Experiences of the CONVERT Phase III randomized trial for good performance status patients with limited-stage small-cell lung cancer

OBJECTIVE

This study is an analysis of the pre-trial quality assurance (QA) exercises submitted by clinicians from radiotherapy (RT) centres across Europe and Canada to qualify for participation in the CONVERT trial.

METHODS

QA exercises submitted by 64 clinicians at 64 RT centres were included in this analysis. The exercises included the completion of a trial-specific questionnaire and submission of a treatment plan, for both trial arms, for a patient fitting the eligibility criteria of the trial. This article describes the QA programme set up for the CONVERT trial and identifies deviations from the trial protocol. Patient eligibility, disease and critical structure outlining and treatment planning technique were assessed.

RESULTS

Results from QA trial-specific questionnaires received between February 2008 and September 2011, returned as part of the QA exercise, indicated that the majority of centres (70.3%) were using 6-MV photons and type B treatment planning system algorithms (57.8%). 90.6% of clinicians assessed submitted data for patients who fitted the eligibility criteria for the trial. There were inconsistencies in outlining of gross tumour volume (GTV) and organs at risk, mainly heart and oesophagus, and in the use of margins around the GTV.

CONCLUSION

Such a QA programme helps to ensure that centres conform to trial protocol and should reduce inconsistencies in RT planning that may confound the results of the CONVERT trial.

ADVANCES IN KNOWLEDGE

Few studies reporting pre-trial QA have been published to date. This article outlines the importance of such a QA programme in the context of multicentre Phase III studies.

The evaluation of low dose hyper-radiosensitivity in normal human skin

BACKGROUND AND PURPOSE

The laboratory phenomenon of low dose hyper-radiosensitivity (LDHRS) describes an excess of cell kill at doses below 1Gy relative to that predicted by the linear quadratic model. These data have stimulated clinical investigation into LDHRS in vivo.

PATIENTS AND METHODS

Skin was used as a model of normal human tissue. Two studies were initiated investigating the response to low doses of radiation. Study 1 compared once daily skin doses of approximately 0.5 and >1.0Gy in 24 patients receiving pelvic radiotherapy. Skin biopsies before and during radiotherapy were analysed histologically to assess the basal cell density (BCD). Study 2 compared two regimens of equal dose/time intensity--an ultrafractionated regimen (0.5Gy TDS x 12 days) with a conventional regimen (1.5Gy OD x 12 days). Skin biopsies taken during treatment assessed BCD and proliferative index. In both studies the changes in BCD were compared using non-linear regression analysis.

RESULTS

Study 1. The results show a significantly greater reduction in BCD in the low dose group when BCD is plotted against dose. This effect is lost when BCD is plotted against time Study 2. The results demonstrate a significantly greater reduction in BCD in the higher dose/fraction arm. The proliferative response was similar in both treatment groups.

CONCLUSIONS

These data suggest that LDHRS does not occur in skin following doses of approximately 0.5Gy/fraction when regimens of equal dose/time intensity are compared. As only small volumes of normal tissue were irradiated it is difficult to predict the biological relevance of this with respect to larger field low dose per fraction irradiation regimens or risk of cancer induction. Equally we cannot extrapolate to effects resulting from exposure to doses <0.5Gy or to the effects of low doses on other endpoints.

A pilot study to assess the feasibility of prior scalp cooling with palliative whole brain radiotherapy

The objective of this work was to perform a feasibility study on the use of scalp cooling during palliative whole brain radiotherapy. Seven patients (1 male, 6 female) with good performance status underwent scalp cooling prior to and during radiotherapy for cerebral metastases. Five patients were prescribed 12 Gy in two fractions and two patients were prescribed 20 Gy in five fractions. Phantom thermoluminescent dosemeter (TLD) studies to assess the build-up effect from the scalp cap were performed. Seven out of eight patients that were offered scalp cooling completed treatment uneventfully. One patient reported discomfort on application of the scalp cap and continued treatment without scalp cooling. No patients reported other adverse effects from use of the cap during treatment or at follow-up. TLD studies demonstrated a 55-80% increase in dose to the scalp after application of the scalp cap. All patients experienced hair loss. Scalp cooling caps are well tolerated through a course of palliative whole brain radiotherapy. The scalp dose is significantly increased owing to a bolus effect from the scalp cap.