Genitourinary Cancer

PV QA 1 - Poster Viewing Q&A 1

SU_32_2321 - Tumor-Targeted Dose Escalation for Localized Prostate Cancer Using MR-Guided HDR Brachytherapy (HDR) or Integrated VMAT (IB-VMAT). Dosimetry and Early Toxicity Analysis.

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Tumor-Targeted Dose Escalation for Localized Prostate Cancer Using MR-Guided HDR Brachytherapy (HDR) or Integrated VMAT (IB-VMAT). Dosimetry and Early Toxicity Analysis.
N. S. Salgado1, C. Menard2, J. Lee3, A. Berlin4, T. Craig1, B. Lao1, A. Rink3, A. J. Bayley5, C. N. Catton4, M. Gospodarowicz4, P. R. Warde6, and P. Chung4; 1Princess Margaret Cancer Center, toronto, ON, Canada, 2Universite de Montreal, Montreal, QC, Canada, 3Princess Margaret Cancer Centre, Toronto, ON, Canada, 4Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada, 5Department of Radiation Oncology, Princess Margaret Cancer Centre-University of Toronto, Toronto, ON, Canada, 6Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada

Purpose/Objective(s): To report dosimetry and early toxicity outcomes of tumor-targeted dose-escalation delivered by integrated VMAT (IB-VMAT) or MR-guided HDR brachytherapy (HDR) boost for prostate cancer.

Materials/Methods: Patients diagnosed with localized prostate cancer, with at least 1 identifiable intraprostatic lesion (> 5mm and <33% total prostate volume) on multiparametric MRI (mpMRI) were enrolled in a prospective non-randomized phase II study. All patients received VMAT to the prostate alone (76 Gy in 38 fractions) plus a GTV boost: IB-VMAT (95Gy in 38 fractions) or MR-guided HDR (10Gy single fraction). GTV was delineated on mpMRI and deformably registered to planning CT scans. CTV76 included prostate plus 5mm margin around the GTV avoiding OARs (penile bulb, urethra, rectum/bladder wall). PTV76 was CTV + 5mm AP/ SI and 3mm LR. PTV95 was GTV + 5mm AP/ SI and 3mm LR (IB-VMAT). PTV10 was GTV(s) + 2 mm SI and 1mm AP/RL (HDR). Comparative dosimetry using EQD2 assuming α/β 3 Gy was performed. For HDR, deformable registration to account for anatomical distortion was used to estimate EQD2 and then summed with the external beam dose. Toxicity data was prospectively collected (CTCAE v.4.0).

Results: 80 patients were enrolled. Dosimetric results are shown below.
VMAT-Integrated Boost (n=40) HDR-Boost (n=40)
Organ Metric Average [Gy] (SD) Average [Gy] (SD)
GTV D99 105.3 (2.8) 103.1 (6.7)
D50 109.4 (1.5) 163.0 (33.8)
D0.1cc 111.7 (1.7) 416.7 (100.5)
PTV (GTV) D99 96.8 (4.3) 95.1 (5.4)
D50 107.5 (1.3) 151.3 (23.8)
D0.1cc 112.2 (1.7) 467.9 (174.5)
PTV Prostate D99 71.6 (1.0) 72.7 (2.0)
D50 81.1 (2.7) 81.6 (2.6)
D0.1cc 112.2 (1.7) 485.3 (209.5)
Rectum Wall D50 16.8 (3.6) 13.6 (6.5)
D0.5cc 79.4 (5.0) 82.6 (4.8)
Bladder Wall D50 16.8 (3.6) 13.6 (6.5)
D0.5cc 77.2 (5.9) 76.2 (4.9)
Urethra D50 86.4 (7.0) 85.4 (5.3)
D0.5cc 87.4 (7.0) 85.7 (6.6)
Penile Bulb D50 8.4 (7.7) 9.7 (8.9)
D0.5cc 29.2 (22.6) 30.0 (24.7)
Median follow-up was 24 months (range 6-36). Acute grade 2 GU toxicity was 40% and 42.5% in IB-VMAT and HDR, while GI toxicity was 7.5% and 10%, respectively. One IB-VMAT patient developed grade 3 GU acute toxicity (urinary retention). Of 69 patients with >12 months follow up (33 IB-VMAT and 36 HDR boost), 18.1% (IB-VMAT) and 19.4% (HDR) developed grade 2 GU toxicity, while grade 2 GI toxicity rates were 6% (IB-VMAT) and 2.7% (HDR). Late grade 3 toxicity was observed in 2 patients (IB-VMAT): 1 GU (hematuria attributable to a new bladder cancer) and 1 GI (rectal ulcer in the context of concurrent HIV antiviral therapy). Deterioration in sexual function occurred in 20% IB-VMAT and 12.5% HDR patients. No statistically significant difference in toxicity was found between the two groups.

Conclusion: Our early results suggest comparable dosimetry to OARs and rates of Grade 2 toxicity between the two boost techniques. HDR boost achieved higher mean and max GTV doses than IB-VMAT. Further follow-up will determine long-term outcomes.

Author Disclosure: N.S. Salgado: None. C. Menard: Research Grant; Siemens Healthcare, Philips, Progenics. Honoraria; Siemens Healthcare. J. Lee: None. A. Berlin: None. T. Craig: None. A. Rink: None. A.J. Bayley: None. C.N. Catton: Research Grant; AbbVie Corporation. Advisory Board; AbbVie Corporation, Bayer Corporation, Estellas Corporation. Chair of Sarcoma Services Committe; CancerCare Ontario. M. Gospodarowicz: None. P.R. Warde: Provincial Head, Radiation Treatment Program; Cancer Care Ontario. P. Chung: Research Grant; Sanofi.

Noelia Salgado, MD

Biography:
Dr. Sanmamed Salgado is currently a clinical-research fellow at the Radiation Medicine Program - Princess Margaret Cancer Centre (Toronto, Canada).
She completed her Medical Degree at Santiago de Compostela University (Spain), and radiation oncology specialty training in Spain, including 3 months as observer at MD Anderson Cancer Center and University of Pennsylvania Hospital in the USA.
After completion of her training, Dr. Sanmamed Salgado worked in Spain (University Hospital of Alava) as a staff radiation oncologist for one year focusing in head and neck, lung, sarcoma and CNS malignancies. In 2017, she moved to Toronto with the goal of improving her clinical and research skills particularly in brachytherapy. During this year Dr. Sanmamed Salgado has grown her interest and focused her practice and research efforts in the treatment of genitourinary malignancies using systemic, stereotactic radiotherapy and brachytherapy approaches. She is an active member in European (ESTRO), Spanish (SEOR), Canadian (CARO) and American (ASTRO) Society of Radiation Oncology. At this stage of her career, Dr. Sanmamed Salgado aims to implement and advance clinical applications for MR-guided brachytherapy methods and research in her home country.

Presentation(s):

Send Email for Noelia Salgado


Assets

SU_32_2321 - Tumor-Targeted Dose Escalation for Localized Prostate Cancer Using MR-Guided HDR Brachytherapy (HDR) or Integrated VMAT (IB-VMAT). Dosimetry and Early Toxicity Analysis.



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Tumor-Targeted Dose Escalation for Localized Prostate Cancer Using MR-Guided HDR Brachytherapy (HDR) or Integrated VMAT (IB-VMAT). Dosimetry and Early Toxicity Analysis.