Stereotactic ablative body radiotherapy for oligometastatic inguinal lymph node in castrate resistant prostate cancer

doi:10.1016/j.ajur.2021.12.004

Asian Journal of Urology, 2023, 10 (1): 109-112 doi: 10.1016/j.ajur.2021.12.004

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Stereotactic ablative body radiotherapy for oligometastatic inguinal lymph node in castrate resistant prostate cancer

Shikha Goyal^*(

),Kannan Periasamy,Renu Madan,Poorva Vias,Vigneshwaran Chandran

Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research, Chandigarh,India

Abstract
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PSMA PET/CECT images. (A) Baseline PSMA PET/CECT of the patient showing enlarged prostate with heterogeneous attenuation (dimensions 3.8 cm×3.9 cm×4.0 cm) with multiple ill-defined intraprostatic PSMA-avid lesions in both lobes (SUV_max 10.3). There was no extracapsular extension, seminal vesicle involvement, pelvic nodal involvement, or distant metastases. (B) PSMA PET/CECT after 6 months of salvage radiotherapy showing no residual disease in prostate bed, pelvic nodes, or distant metastases. (C) PSMA PET/CECT at follow-up showing two small adjacent PSMA-avid nodes in left inguinal (SUV_max 12.2, size 1.1 cm×1.5 cm) and left lateral external iliac (SUV_max 10.3, sub-centimeter size) regions. PSMA, prostate-specific membrane antigen; PET/CECT, positron-emission tomography/contrast-enhanced computed tomography; SUV_max, maximum standardized uptake value.

Plan for stereotactic ablative body radiation therapy to left inguinal lymph nodes in a case of castrate resistant prostate cancer with oligometastatic disease. (A) Axial view; (B) Coronal view; (C) Sagittal view. Prostate-specific membrane antigen avid enlarged left inguinal nodes were delineated as GTV. PTV was generated around GTV with 1 cm margin, with modification at natural barriers. Organs at risk included a subcutaneous strip in left inguinal region, left femur head, bladder, and rectum. A dose of 25 Gy in five fractions was prescribed to 95% of PTV (BED_1.5=108.33 Gy, EQD2=46.4 Gy). Simultaneous integrated boost of 35 Gy was prescribed to 99% of GTV (BED_1.5=151.67 Gy, EQD2=65 Gy). (D) DVH of the plan showing the achieved target and organ at risk doses. DVH, dose volume histogram; GTV, gross tumor volume; Min, minimum; Max, maximum; PTV, planning target volume; BED_1.5, biologically equivalent dose assuming α/β ratio of 1.5 for prostate cancer; EQD2, 2-Gy equivalent dose; A?, anterior; P, posterior; R, right; F, foot-end.

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