Standardisation of radiotherapy to inguinal and pelvic lymph nodes in locally-advanced cancer of the penis, as defined by the International Penile Advanced Cancer Trial (InPACT).

Abstract

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, radiotherapy protocols for this rare cancer lacked consistency and standardisation, necessitating multi-centre, international collaboration to develop comprehensive Radiotherapy Planning, Delivery and Quality Assurance Guidelines.

Methods: InPACT has two main aims; to establish the efficacy of neoadjuvant chemotherapy or chemoradiotherapy in patients with macroscopically-involved inguinal nodes. Secondly, to compare prophylactic pelvic lymph node dissection (PLND) 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 radiotherapy 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 radiotherapy quality assurance for each participating centre.

Results: International consensus radiotherapy guidelines were established, encompassing risk status assessment and indications for each treatment region based on radiological and pathological 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.

Conclusion: The InPACT radiotherapy guidelines offer a step towards international consensus on contouring for inguino-pelvic radiotherapy in penile cancer.