Evaluation of response after pre-operative radiotherapy in soft tissue sarcomas; the European Organisation for Research and Treatment of Cancer – Soft Tissue and Bone Sarcoma Group (EORTC – STBSG) and Imaging Group recommendations for radiological examination and reporting with an emphasis on magnetic resonance imaging

Abstract

At present, there is no standardised approach for the radiological evaluation of soft tissue sarcomas following radiotherapy (RT). This manuscript, produced by a European Organisation for Research and Treatment of Cancer-Soft Tissue and Bone Sarcoma Group (EORTC-STBSG) and Imaging Group endorsed task force, aims to propose standardisation of magnetic resonance imaging techniques and interpretation after neoadjuvant RT for routine use and within clinical trials.

Preoperative radiotherapy in soft tissue sarcoma: from general guidelines to personalized medicine

“…Although the above mentioned late outcomes measures can be considered as robust endpoints, but they take years to observe. Surrogate early end-points provide an alternative assessment strategy, represented by outcomes such as the pathological evaluation of the resection specimen, wound complications, and potential signals from sophisticated imaging techniques (38)(39)(40)(41). There is a need for prospective clinical studies incorporating these aspects with the purpose of validation.…”

Imaging in retroperitoneal soft tissue sarcoma

“…Limitations of tumor size measurements has led to some pilot studies of FDG PET/CT and several show promising results although large scale evidence is challenging in this rare and heterogeneous group of tumors. Diffusion weighted MRI which is a simple, robust and non‐invasive technique has also been shown to detect and quantify early treatment in many tumor types but has not yet been proven in RPS although trials are underway …”

“…Histopathological changes including necrosis, cystic change, haemorrhage, hyalinization, and fibrosis which occur following RT may cause tumors to increase in size resulting in pseudoprogression. With the exception of myxoid liposarcomas significant dimensional radiologic responses after preoperative RT are rare and have been reported as low as 0% . Miki et al showed that 31% of tumors increased in size by more than 10% but this was not associated with deterioration in local recurrence free survival, event free survival or overall survival.…”

“…However it is important to assess signal characteristics from multiple MRI sequences in combination. For example diminished enhancement and reduction in size of restricted components/rising Apparent Diffusion Coefficient (ADC) on DWI may be interpreted as response . Areas of new enhancement should be interpreted with caution as this can arise secondary to vascular disruption following radiotherapy and does not necessarily reflect progression.…”

“…For example diminished enhancement and reduction in size of restricted components/rising Apparent Diffusion Coefficient (ADC) on DWI may be interpreted as response. 41 follow up should be at least 10 years or even indefinite. 8 Particularly for younger patients where the radiation risks from multiple CT examinations might cause concern, follow up can be performed with MRI of the abdomen and pelvis with low dose CT thorax.…”