Multimodality treatment of locally advanced penile cancer: A contemporary dosimetric comparison and case presentation.

Abstract

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.