346 Background: There is a paucity of data on the optimal therapy for locally advanced penile cancer (PC). However, advances in other HPV associated neoplasms utilizing combined modality therapy (CMT) have been encouraging. We describe the management of advanced PC with such an approach. Methods: The patient presented following partial penectomy and inguinal dissection with T2N3 disease and extra-capsular extension (ECE). In a multi-disciplinary setting, it was decided to treat him post-operatively with concurrent chemoradiation. CT data sets were used for dosimetric comparison of critical structures (small bowel, rectum, bladder, scrotum, testes, bone marrow, skin, bowel, and femoral heads) and plans were generated using conventional penile fields (3D), Intensity Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT), minimizing dose to organs at risk while optimizing treatment dose. Results: The patient was treated with IMRT (45 Gy to penile stump, pelvic and inguinal nodes (INs) with a 9 Gy boost to left INs and 15 Gy boost to right INs, due to ECE) and weekly Cisplatin (20 mg/m2). IMRT gave similar coverage and avoidance of normal structures compared to VMAT but with lower mean scrotal dose ( IMRT 27.0 Gy , VMAT 29.9 Gy, 3D 45.6 Gy). There was no >grade II toxicities, with grade II scrotal edema and moist desquamation of bilateral inguinal folds, not requiring treatment breaks. Acute RT toxicities had near resolution at 1 month. The IMRT and VMAT plans vs. the 3D plan had lower mean doses to the normal structures. 3D planning had unacceptable max doses to femoral head (62 Gy) and scrotum (55 Gy). Small bowel, V15Gy ≤ 150 cc was achieved by all plans. Dose homogeneity was improved for IMRT/VMAT vs. 3D planning (max dose 119%). Conclusions: This is one of the first comparisons of contemporary radiation techniques in the multimodality setting of PC. We demonstrate that utilizing IMRT concurrently with Cisplatin is feasible and well tolerated suggesting it a reasonable strategy to obtain durable local control, without which the prognosis is uniformly dismal. Larger studies are warranted to explore this contemporary CMT approach to locally advanced PC.
e561 Background: pPRT increases local control, biochemical progression free survival, and even overall survival in patients with adverse features undergoing prostatectomy. The Radiation Therapy Oncology Group (RTOG) consensus definition of the clinical target volume (CTV) in 2010 was based on patterns of failure and anatomy without consideration of pre-operative imaging. This results in large volumes of bladder in the treatment field. Our study evaluates whether incorporation of pre-operative prostate volume can reduce the post-operative CTV and minimize dose to adjacent normal tissue. Methods: We reviewed records of all patients with available pre-operative pelvic CT scans treated at our institution with pPRT. The pre-operative CT scan was fused to the simulation CT. Post-operative CTV (CTV1) was delineated based on RTOG guidelines. A separate CTV (CTV2) was constructed, based on the intact prostate and proximal seminal vesicles. Plans were constructed for each CTV and doses to rectum, bladder, and penile bulb calculated, as well as concordance between the two CTVs and planning target volumes (PTVs). Paired student’s t-test was used to calculate difference between doses in the two different plans. Results: 10 patients’ plans were analyzed. Dosimetric parameters are shown in table 1. Volume of the bladder receiving 65 Gy or higher (V65) was significantly higher in CTV1. As would be expected, there were no significant differences in dose to either the rectum or penile bulb. Additionally, there was on average only 39% overlap between the CTVs and 60% between the PTVs in the two plans. Conclusions: Utilization of the pre-operative pelvic CT scan can aid in more accurate delineation of the CTV/PTV in prostate bed radiation therapy and decrease the bladder dose. As many patients at risk for pPRT have had this imaging performed preoperatively, in accordance with guidelines, incorporation of this data appears prudent. These findings need to be validated in a larger cohort. [Table: see text]
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