Standardization of radiation therapy to Inguinal and Pelvic Lymph Nodes in Locally Advanced Cancer of the Penis, as Defined by the International Penile Advanced Cancer Trial (InPACT).

Purpose: InPACT addresses the optimal management of locally advanced penile cancer, aiming to prospectively evaluate the relative benefits and sequencing of surgery, chemotherapy, and chemoradiotherapy. At trial inception, radiation therapy protocols for this rare cancer lacked consistency and standardization, necessitating multicenter, international collaboration to develop comprehensive radiation therapy planning, delivery, and quality assurance guidelines.

Methods and materials: InPACT has 2 main aims; to establish the efficacy of neoadjuvant chemotherapy or chemoradiotherapy in patients with macroscopically-involved inguinal nodes. Second, to compare prophylactic pelvic lymph node dissection plus chemoradiation to the inguinal and pelvic fields versus chemoradiation alone in patients whose inguinal node histology predicts a high risk of occult pelvic node involvement. The primary outcome measure for the trial is survival time. An international group was convened to achieve consensus on radiation therapy contouring, planning, dose, fractionation, and delivery for this rare cancer. These guidelines have been used throughout the conduct of the trial to date and form part of the radiation therapy quality assurance for each participating center.

Results: International consensus radiation therapy guidelines were established, encompassing risk status assessment and indications for each treatment region based on radiological and pathologic risk status of nodal basins. Guidance provides a nodal contouring atlas, addresses prepubic fat coverage, and specifies dose fractionation for both neoadjuvant and adjuvant settings, including recommendations for macroscopic disease. Trial recruitment is ongoing. Oncological and toxicity outcomes will be reported in due course.

Conclusions: The InPACT radiation therapy guidelines offer a step toward international consensus on contouring for inguino-pelvic radiation therapy in penile cancer.