Volumetric modulated arc therapy (VMAT) provides the conformality that enables three separate simultaneous pelvic malignancies to be treated radically–a case study

Abstract

Radiotherapy and surgery are both potential modalities for the definitive treatment of pelvic malignancies. Although surgery provides a histological specimen, enabling exact staging, radiotherapy is sometimes preferred as it provides patients the opportunity for organ conservation and therefore perhaps better quality post-treatment survivorship. Our case report details how three separate primary pelvic cancers (prostate, rectal, anal) in one patient were treated simultaneously with definitive radiotherapy. Patient was prescribed 80 Gy in 40 fractions to the planning target volume (PTV) prostate, 54 Gy to PTV anal canal, 45 Gy to the pelvis including PTV rectosigmoid junction and 36 Gy to the PTV inguinal lymph nodes that encompassed clinically negative nodes draining the anus, through the Volumetric Modulated Arc Therapy (VMAT) with 6MV photons. Mean doses to organs at risk (OAR) are 30.01 Gy to the bowel volume, 46.54 Gy to the bladder, 30.42 Gy to the femurs, and 61.84 Gy to the rectum. Radiation doses to the prostate and anal canal are consistent with conventional treatment doses with definitive radiotherapy. The rectal dose was accepted as part of the definitive treatment of rectal cancer following Endoscopic Mucosal Resection (EMR). This could only be achieved through the superior dose conformality of VMAT, maximising the dose given to tumour bearing PTV while minimising the dose to OARs which included normal pelvic structures. All three cancers remained under control at 4 years after treatment, with minimal late toxicity associated with the treatment received. Further RCTs in pelvic malignancies are needed to help clinicians and patients select the best treatments, to improve disease control while maintaining quality of survivorship.