Patterns of practice regarding use of radiation therapy following radical prostatectomy: A survey of Radiation Oncologists and Urologists in Australia and New Zealand.

INTRODUCTION: This study aimed to investigate the patterns of practices of radiation oncologists (ROs) and urologists in Australia and New Zealand with respect to the utilisation of post-prostatectomy radiation therapy (RT) and help guide the development of an update to the existing Faculty of Radiation Oncology Genito-Urinary Group post-prostatectomy guidelines. METHODS: ROs and urologists with subspecialty practice in prostate cancer from Australia and New Zealand were invited to participate in an online survey comprised of clinical scenarios regarding post-prostatectomy RT. RESULTS: Sixty-five ROs and 28 urologists responded to the survey. In the setting of low-risk biochemical relapse, the threshold for initiating RT was lower for ROs than urologists. ROs were more likely than urologists to recommend adjuvant RT for node-positive disease. When salvage RT was advised for a pT3N0R1 recurrence, there was no consensus amongst ROs on whether to add either ADT or nodal treatment over prostate bed RT alone. For a solitary PSMA-avid pelvic lymph node recurrence, whole pelvis RT with androgen deprivation therapy was the preferred treatment option (72% ROs, 43% urologists). Most ROs (92%) recommended conventionally fractionated RT to 66-70 Gy, with a boost to any PSMA PET avid recurrent disease. CONCLUSION: This survey highlights the marked discordance in practice for the management of prostate cancer relapse post-prostatectomy. This is seen not only between specialties but also within the radiation oncology community. This emphasises the need for an updated evidence-based guideline to be produced.

Inter- and intra-fraction motion in stereotactic body radiotherapy for spinal and paraspinal tumours using cone-beam CT and positional correction in six degrees of freedom.

INTRODUCTION: Stereotactic body radiotherapy (SBRT) for spinal tumours delivers high doses per fraction to targets in close proximity to neural tissue. With steep dose gradients, small changes in position can confer significant dosimetric impact on adjacent structures. We analysed positioning error in consecutively treated patients on a strict image-guidance protocol with online correction in 6 degrees of freedom (6-DOF). METHODS: Set-up error, residual error post-correction and intra-fraction motion for 30 courses of spinal SBRT in 27 patients were assessed using cone-beam CT. Positional error was corrected in x, y and z translational planes and rotational axes using a robotic couch, applying 2 mm and 2° action levels. Linear mixed-effects model assessed whether positional error was influenced by factors such as vertebral level, immobilisation device and treatment duration. RESULTS: Sixty-two fractions were delivered with 225 image registrations. Median treatment duration was significantly longer for patients treated with static-field intensity-modulated radiotherapy compared with volumetric-modulated arc treatment--40 min versus 28 min, respectively (P = 0.01). Across all fractions, the median residual positional error after initial correction was greatest in the x translational plane (0.5 mm; 95% confidence interval (CI) 0.3-0.6) and y rotational axis (0.25°; 95% CI 0.1-0.3). Median intra-fraction error was also greatest in the x-plane (0.7 mm; 95% CI 0.5-1.0) and y-axis (0.4°; 95% CI 0.2-0.5). CONCLUSION: With strict immobilisation, image-guidance and 6-DOF correction, our current practice of applying 3-mm planning margins for target volumes and critical structures appears safe. Lower image-guidance action thresholds plus verification with end-to-end testing would be recommended before further reducing margins.

Technique and early clinical outcomes for spinal and paraspinal tumours treated with stereotactic body radiotherapy.

We report technique and early clinical results of stereotactic body radiotherapy (SBRT) from Princess Alexandra Hospital. SBRT involves the precise delivery of highly conformal and image-guided external beam radiotherapy with high doses per fraction. It is increasingly being applied in management of spinal tumours. Thirty-six courses of spine SBRT in 34 patients were delivered between May 2010 and December 2013. Mean patient age was 58 years. Treatment was predominantly for metastatic disease, applied in de novo (n=22), retreatment (n=14) and postoperative (n=8) settings. Prescribed doses included 18-30 Gy in 1-5 fractions. SBRT technique evolved during the study period, resulting in a relative dose escalation. No severe acute toxicities were observed. At median follow-up of 7.4 months (range: 1.7-22.2), no late radiation myelopathy was observed. Risk of new/worsening vertebral compression fractures was 22% (n=8) and was significantly associated with increasing Spinal Instability Neoplastic Scores (p=0.0002). In-field control was 86% with relapse occurring at a median interval of 2.8 months (range: 1.9-4.7). Thirteen patients (36%) died and median overall survival has not been reached. SBRT is an evolving technology with promising early efficacy and safety results. The outcomes of this series are comparable with international literature, and await longer follow-up.

The impact of preradiation residual disease volume on time to locoregional failure in cutaneous Merkel cell carcinoma--a TROG substudy.

PURPOSE: This study evaluated the impact of margin status and gross residual disease in patients treated with chemoradiation therapy for high-risk stage I and II Merkel cell cancer (MCC). METHODS AND MATERIALS: Data were pooled from 3 prospective trials in which patients were treated with 50 Gy in 25 fractions to the primary lesion and draining lymph nodes and 2 schedules of carboplatin based chemotherapy. Time to locoregional failure was analyzed according to the burden of disease at the time of radiation therapy, comparing patients with negative margins, involved margins, or macroscopic disease. RESULTS: Analysis was performed on 88 patients, of whom 9 had microscopically positive resection margins and 26 had macroscopic residual disease. The majority of gross disease was confined to nodal regions. The 5-year time to locoregional failure, time to distant failure, time to progression, and disease-specific survival rates for the whole group were 73%, 69%, 62%, and 66% respectively. The hazard ratio for macroscopic disease at the primary site or the nodes was 1.25 (95% confidence interval 0.57-2.77), P=.58. CONCLUSIONS: No statistically significant differences in time to locoregional failure were identified between patients with negative margins and those with microscopic or gross residual disease. These results must, however, be interpreted with caution because of the limited sample size.