Imaging technologies are crucial in evaluating a patient’s response to cancer treatment in daily oncology practice. This can be done quite effectively for most tumours using Response Evaluation Criteria in Solid Tumours (RECIST). However, RECIST criteria work well for tumours located in visceral organs or soft tissues (assessed by computed tomography), but not so well for bone metastases which are frequently present, especially in prostate and breast cancers. More effort, therefore, is needed to improve understanding of how to monitor the response of bone metastases to treatment using magnetic resonance imaging (MRI) and positron emission tomography (PET), and a recent European Organisation for Research and Treatment of Cancer (EORTC) Imaging Group review and position statement published in the European Journal of Cancer is a decidedly welcome contribution.
The paper published by the EORTC Imaging Group investigators highlights the most recent developments in MRI and PET and elucidates how these techniques can be used to detect bone metastases at an early stage as well as monitor the response to treatment. The EORTC investigators describe the current state of the art in PET and MRI, the strengths, weaknesses and complementarity of various imaging techniques with respect to specific indications, and recommendations for choosing the most appropriate imaging technique.
Bone metastases, which frequently represent the only site of metastases, are an exception in response assessment systems, because of the nature of the fixed bone defects, their complexity, which ranges from sclerotic to osteolytic and because of the lack of sensitivity, specificity and spatial resolution of the previously available bone imaging methods, mainly bone scintigraphy.
MRI and PET to detect early infiltration by cancer
Techniques such as MRI and PET are able to detect the early infiltration of the bone marrow by cancer, and to quantify this infiltration using morphologic images, quantitative parameters and functional approaches.
According to Prof. Frederic Lecouvet of the Cliniques Universitaires Saint Luc in Brussels, Belgium and lead author of the EORTC review and position statement, “Assessing the response of metastases to treatment is something we do on a day to day basis, both in our oncology practice as well as for clinical trials. If the metastases occur in soft tissues, then we already have validated criteria, such as RECIST, that enable us to evaluate the response. A host of problems, however, limits our ability to measure the response to treatment of metastases found in bone. These range from the characteristics of bone metastatic disease, the structure of bone itself, to the sensitivity, specificity, and resolution of imaging methods available until now. We hope to resolve these issues, and our review is a step in the right direction.”
This new EORTC position paper proposes recommendations for the choice of the most adequate imaging technique. The efforts of the EORTC researchers will go a long way towards making MRI and PET techniques a routine part of oncology practice.
Lecouvet FE, Talbot JN, Messiou C, et al. Monitoring the response of bone metastases to treatment with Magnetic Resonance Imaging and nuclear medicine techniques: A review and position statement by the European Organisation for Research and Treatment of Cancer Imaging Group. Eur J Cancer 2014; Published online August 16. DOI: dx.doi.org/10.1016/j.ejca.2014.07.002