N. Rosenfelder

Comparison of setup accuracy and intrafraction motion using stereotactic frame versus 3-point thermoplastic mask-based immobilization for fractionated cranial image guided radiation therapy

PURPOSE Prospectively compare patient setup accuracy and intrafraction motion of a standard 3-point thermoplastic mask with the Gill-Thomas-Cosman relocatable stereotactic frame, during fractionated cranial radiation therapy using the ExacTrac system (Brainlab AG Feldkirchen, Germany) for daily online correction. METHODS AND MATERIALS The number of fractions with all postcorrection and post-treatment errors <2 mm was assessed in 21 patients undergoing fractionated stereotactic radiation therapy (13 frame setup, 8 mask setup) using daily online correction. Achievable patient setup accuracy and total intrafraction motion were evaluated. The relative contributions of movement during floor rotation and patient movement to intrafraction motion were calculated. RESULTS With daily online correction, patient setup margins can be reduced from 1, 5, and 4 mm in the lateral, longitudinal, and vertical axes for mask setup and from 1-2, 2, and 1 mm, respectively, for frame setup to <1 mm isotropically for either immobilization system. Intrafraction movement was small for frame setup (mean [SD], -0.3 [0.3], -1.1[0.4], and -0.2 [0.6] in lateral, longitudinal and vertical axes, respectively; maximum, -2.7 mm [longitudinal axis]), and mask-setup (mean [SD], -0.4 [0.5], -0.8 [0.7], and 0.0 [0.3], respectively; maximum, -2.0 mm [longitudinal axis]) and is mainly due to floor rotation. Postcorrection and post-treatment errors were all <2 mm in 95% and 99% of fractions in the mask and frame, respectively, meeting the criteria for a 3-mm clinical target volume-planning target volume margin for either immobilization method. CONCLUSIONS Daily online correction can compensate for less precise immobilization and permits stereotactic margins to be used for standard thermoplastic masks without the need for specialized mask systems.

Intensity modulated radiation therapy allows prostate and dose-escalated pelvic radical radiation therapy after renal transplantation

Collateral dose to neighboring tissues limits the deliverable dose of radiation therapy (RT) to the target. Native kidneys receive a minimal dose during standard pelvic lymph node (PLN) RT, because the superior field border is at the L4/5 vertebra for inclusion of internal/external iliac nodes and at the aortic bifurcation for common iliac nodes, both of which are infrarenal. However, a pelvic transplanted kidney may be considered a relative contraindication to radical (curative) pelvic RT. The incidence of radiation-associated renal injury is likely to be underreported because of its long latency, the nonspecific symptoms of renal impairment, and the multifactorial confounding risks. Current dose constraints are based on data from the 1980s to 1990s.1-3 For a native kidney, the risk of late radiation toxicity increases with volume of treated kidney and radiation dose. Recommendations are that one-third or less of the kidney should receive ≥ 50 Gy, whereas two-thirds or less should receive 30 Gy and the whole kidney no more than 23 Gy. A median dose b 17.5Gy is recommended to reduce the risk of

Target definition in salvage postoperative radiotherapy for prostate cancer: 18F-fluorocholine PET/CT assessment of local recurrence

Abstract Purpose: Inadequate clinical target volume (CTV) definition is likely to be a major contributing factor to local recurrence (LR) rate after radiotherapy. Our aims were to identify sites of prostate cancer LR in biochemical recurrence post-prostatectomy using 18F-Fluorocholine (18F-FCH) positron emission tomography/computed tomography (PET/CT) and to compare different CTV-delineation guidelines in a cohort of postoperative patients. Material and methods: Thirty-six patients presenting with LR within the prostatic bed on 18F-FCH PET/CT between 10/2011 and 06/2016 were included in this retrospective study. Median PSA at the time of 18F-FCH PET/CT was 2.7 ng/mL (0.8–9.4) and median PSA doubling time was 11 months (3–28). For each patient, the CTVRTOG, CTVFROGG and CTVEORTC following the corresponding guidelines were outlined and compared. Forty-one LR were delineated using a gradient-based method and the percentage of FCH uptake included in each CTV was evaluated. Results: The anastomosis was the most common recurrence site (52.8%), followed by the retrovesical region (31.7%) and the bladder neck (7%). The median SUV max value was 4.8 (2.3–16.1). The percentage of LR entirely included in the CTVRTOG was not significantly different from that included in the CTVFROGG (84% versus 83%, p = .5). Significantly more recurrences were included in the CTVRTOG volume compared to the CTVEORTC (84% versus 68%, p=.006), due to a better coverage of the bladder neck and retrovesical regions. Six out of 10 relapses occurring in the posterior region of the anastomosis were not covered by any of the CTVs. Conclusions: In our study, the CTVRTOG and CTVFROGG ensured the best coverage of LR seen on 18F-FCH PET/CT. When outlining the prostatic fossa, greater coverage of the posterior vesico-urethral region may allow better coverage of potential microscopic disease.

1011 poster DOES MARKER-BASED PROSTATE RADIOTHERAPY CAUSE WORSE ACUTE TOXICITY?

lymph nodes. Hormone therapy included ablation (surgical or pharmacological) or maximal androgen blockade (MAB) but for group when was combined with RT was started at least 2 months before RT and continued concurrently and then administered in adjuvant fashion for minimum duration of 24 months. Results: The 5-year overall survival (OS) was 75% in combined (HT + RT) arm and 59% in HT, respectively (p= 0.03). Median overall survival time was 62.2 months in HT alone arm and 70.8 months in combined treatment. Actuarial 5-year cancer specific survival (CSS) was 83% in (HT + RT) group and 70% in HT group (p= 0.01). Actuarial 5-year distant metastases-free survival in (HT + RT) was 79% and 54% in HT alone group (p= 0.007). Median biochemical progression-free survival for HT group was 34 months and 59.4 months in HT + RT group (p= 0.000). Conclusions: Combined treatment with hormone therapy and radiotherapy shows benefit when compared with hormone therapy alone in terms of overall survival, cancer specific survival, distant metastases-free survival and biochemical progression-free survival. Acute and late treatment toxicity level in combined arm was low and in addition had now adverse effect on quality of life measures when compared to hormone therapy alone.