Yttrium 90 Microsphere Selective Internal Radiation Treatment of Hepatic Colorectal Metastases

We read with interest the review of yttrium 90 microsphere selective internal radiation treatment (SIRT) by Gulec et al.¹ The authors discussed the administration technique, benefits, and complications of SIRT. They note the importance of combining SIRT with chemotherapy, in particular 5-fluorouracil (5-FU) as a radiosensitizer, and recommend chemotherapy be given in “close temporal proximity to the radiation.” In conclusion they state that SIRT has a potential role in the multimodality treatment of unresectable colorectal cancer metastases, but further data are required to determine the optimal strategy of multimodality treatment. We have recently reviewed the topic of combining chemotherapy and SIRT and found there is a lack of guidance in the literature on the appropriate timing of chemotherapy administration in relation to SIRT. In the most recent report, SIRT was administered in combination with 5-FU and oxaliplatin.² There is, however, a theoretical risk of arterial spasm when administering 5-FU at the time of hepatic arterial access for SIRT delivery. While there are no reported arterial events in the current literature, arterial complications related to 5-FU are common. Südhoff et al³ performed high-resolution ultrasonography of the brachial artery in 30 patients receiving 5-FU. Contraction of the brachial artery occurred in 50% of patients, confirming that systemic arterial vasoconstriction beyond the heart is common in patients receiving 5-FU. We believe there is a need to define the timing of 5-FU administration in relation to SIRT in a more standardized fashion, taking into account this potential toxicity, before the role of SIRT in the multimodality treatment of unresectable hepatic colorectal metastases can be defined.