ESTRO 37 Abstract book

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ESTRO 37

Purpose or Objective The dose to the bladder neck (BN) has been suggested to be a predictor of urinary toxicity. Magnetic resonance imaging (MRI) is one of the best imaging modalities to delineate the BN. We aim to assess the impact of the dose to the BN on physician and patient-reported urinary toxicity after MRI-guided high dose-rate brachytherapy (HDR-BT) boost. Material and Methods Fifty-one patients were treated with a single 15-Gy MRI- guided HDR-BT implant followed by external beam radiotherapy (EBRT) as part of a prospective phase II clinical trial. MRI-based treatment planning was used. The clinical target volume (CTV) was defined as the prostate and a 2mm craniocaudal extension was added to generate the planning target volume (PTV). Urethra, bladder, rectum and penile bulb were contoured as organs at risk (OARs) and dosimetric parameters collected prospectively. The BN was delineated in retrospect on T2-weighted images by the same radiation oncologist and reviewed by an independent physician. Acute (≤3 months) toxicity and health-related quality of life (HRQoL) data were collected prospectively using CTCAE v.4 and the expanded prostate index composite (EPIC) respectively. A minimally important difference (MID) was defined as a deterioration of HRQoL scores at 3 months compared to baseline ≥ 0.5 standard deviation of baseline score. Linear and logistic regression models were used as appropriate to assess the impact of BN dose on urinary toxicity and HRQoL. A two-tailed p -value ≤0.05 was considered statistically significant. Results The median BN volume was 0.6 cc [interquartile range (IQR): 0.4-0.7]. The median maximum dose to the BN (BNDmax) and urethra (UDmax) was 20.5 Gy (IQR 17.9- 26.1) and 19.8 Gy (IQR 18.8- 21.0) respectively. The median dose to 0.5cc of the urethra (UD0.5) was 17.3 Gy (IQR:16.6-17.3). On univariate linear regression analysis, BNDmax was not significantly associated with any of the urethral dose parameters. In addition only 5.9% of the total amount of variation in BNDmax was explained by the UDmax (R 2 =0.059, p =0.09). Acute grade 2+ urinary toxicity was observed in 30% of patients. Among those, 2 patients had an acute urinary retention. No grade 4+ toxicity was reported. Furthermore 44% of patients reported a MID in EPIC urinary domain score at 3 months. None of the dosimetric parameters including BNDmax was associated with acute grade 2+ urinary toxicity or MID. However, the 2 patients with urinary retention had a BND max in the highest quartile; 28.3 and 26.4 Gy (>175% of prescription dose). Conclusion While a high BN dose was observed in patients who had an acute urinary retention in our cohort, the predictive value of this parameter is yet to be determined in a larger cohort of patients. Meanwhile, with the increased use of MRI in brachytherapy treatment planning, it is worthwhile delineating the BN and paying appropriate caution to doses delivered to this anatomical structure. PV-0259 Impact of an additional chemotherapy cycle during brachytherapy in cervical cancer patients A. Escande 1,2 , S. Bockel 2 , M. Khettab 2 , E. Manea 2 , I. Dumas 2 , R. Mazeron† 2 , A. Schernberg 2 , E. Deutsch 2 , P. Morice 3 , C. Haie-Meder 2 , C. Chargari 4,5 1 Centre Oscar Lambret, Academic Department of Radiation Oncology, Lille, France 2 Gustave Roussy, Brachytherapy Unit-Radiotherapy Department, Villejuif, France 3 Gustave Roussy, Surgery Department, Villejuif, France 4 Institut de Recherche Biomédicale des Armées, Bioradiology, Bretigny-sur-Orge, France 5 French Military Health Academy, Ecole du Val-de-Grâce, Paris, France

Purpose or Objective Definitive concurrent chemoradiation (CRT) plus image- guided adaptive brachytherapy (IGABT) is the standard treatment for locally advanced cervical cancers (LACC). Metaanalyses examining the benefit of CRT found that the larger survival improvement was for FIGO stages Ib-IIb tumors. However, the optimal number of chemotherapy (CT) cycles is not well defined and no data is available on the benefit of an additional cycle during IGABT. These issues were assessed in a large single center cohort of patients (pts). Material and Methods Clinical records of 260 pts treated from 2004 to 2016 for a LACC were reviewed. Patients received CRT delivering 45 Gy in 25 fractions +/- lymph node boost. If not contraindicated, concurrent cisplatin 40 mg/m² was delivered weekly. Carboplatin AUC2 was preferred in case of renal function impairment. An additional cycle could be delivered during pulse dose rate (PDR) IGABT. The impact of total number of CT cycles on overall, disease-free, local relapse-free, regional relapse-free and distant metastasis -free survival (OS, DFS, LRFS, RRFS, DMFS, respectively) was examined using survival estimation model by Kaplan-Meier, log-rank tests and Cox proportional-hazards model. Results Median number of CT cycles was 5 (Interquartile 25-75 [IQ]: 4-5). A cycle was delivered concurrently with IGABT in 115 patients (44.2%). Median overall treatment time was 48 days (IQ: 44–52). With median follow-up of 5 years (4.5-5.4), estimated OS and DFS at 5 years were 72.0% (95%CI 60.6–83.4) and 63.3% (95%CI 51.0–75.6), respectively. In univariate analysis, receiving ≥ 5 cycles was associated with longer OS (p=0.000), DFS (p=.000), and improvement in time to local failure (p=.000), and distant failure (p=.000). In multivariate analysis (including nodal involvement, differentiation, neutrophilia, anemia, BMI>25), number of CT cycles ≥ 5 correlated with a longer OS (p=.000), DFS (p=.003), LRFS (p=.001), RRFS (p=.001) and DMFS (p=.004). When categorizing population according to high-risk clinical target volume (HR-CTV) (< or ≥ 30cm 3 ), number of CT cycle ≥ 5 remained correlated with DFS, LFS and DMFS for both groups, although the effect was higher in case of bulky HR-CTV. The effect on OS and RRFS was significant only in pts with bulky HR-CTV (p=0.000). In multivariate analysis, the effect of number of cycles on OS and DFS was significant only in pts with HR-CTV volume ≥ 30cm 3 (HR=0.201; 95%CI 0.09-0.452 and HR=0.238; 95%CI 0.116- 0.486, respectively). Conclusion Number of concurrent CT cycles should be ≥ 5. PDR IGABT permits to deliver an additional cycle during brachytherapy boost (52.1% of pts received their 5 th cycle during IGABT). PV-0260 On the implementation of IGBT for cervix cancer in the observational multicenter study EMBRACE N. Nesvacil 1 , K. Tanderup 2 , R. Pötter 1 , Y. Seppenwoolde 1 , A. De Leeuw 3 , J. Swamidas 4 , I. Dumas 5 , R. Hudej 6 , G. Lowe 7 , I. Jürgenliemk-Schulz 3 , J. Lindegaard 2 , C. Kirisits 1 1 Medical University of Vienna, Department of Radiotherapy- CCC- Christian Doppler Laboratory for Medical Radiation Research, Vienna, Austria 2 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark 3 University Medical Centre Utrecht, Department of Radiation Oncology, Utrecht, The Netherlands 4 Tata Memorial Hospital, Department of Radiation Oncology, Mumbai, India 5 Gustave Roussy- University Paris-Saclay, Department of Medical Physics, Paris, France 6 Institute of Oncology, Department of Radiotherapy, Ljubljana, Slovenia