Caren van Roekel

277 Discussion lesions may be fused at follow-up evaluation. Both anatomical and metabolic response-rates have been related to OS. Yet, agreement between both methods is often lacking, with metabolic response generally overestimating anatomic response (101), as was also seen in our dose-response study. For radioembolization, metabolic response is believed to be the best assessment method, as this is not hampered by the presence of necrosis, cystic changes and hemorrhage, which can be the case with size evaluation (102). An alternative, more individualized approach to response evaluation is depth of response (DpR). This indicates the maximum tumor shrinkage observed in a patient, compared with baseline. The extent of tumor response is quantified and it is a continuous measure that can also become negative (in case of tumor growth). It can be based on tumor volume or size (100). In retrospective and prospective studies on systemic therapy for mCRC patients, DpR was significantly associated with post-progression survival (PPS) and OS (100, 103, 104). In theory, DpR could also be used for response evaluation after radioembolization. However, the largest reduction in tumor size or volume is generally observed after first-line treatment. Therefore, its use may be optimal when radioembolization is performed in a first-line setting. Although response to treatment obviously is of paramount importance, so is the development of quality of life. As patients receiving radioembolization are generally in a palliative stage, quality of life is extremely important. Treatment selection should be based on expected gain in survival AND adverse event profile. In our review on studies reporting quality of life after treatment with radioembolization, most included studies reported no significant change in quality of life (105). Our own study results are compliant with this finding: although there was a decline in quality of life after one week, overall, quality of life was not significantly affected over time (105). Based on these findings in palliative patients, the impact of radioembolization on quality of life is limited. The impact of radioembolization in addition to chemotherapy was investigated in the first line setting as well. In the SIRFLOX, FOXFIRE and FOXFIRE-Global studies, quality of life was assessed at baseline, three months, six months, 12 months and 24 months. In the patient group that was treated with both radioembolization and chemotherapy, quality of life was significantly lower compared with the chemotherapy group at three months post-treatment. After 10