The vascular invasion is common in advanced renal cancer, which is associated with elevated morbidity and mortality. The surgical challenging radical nephrectomy and thrombectomy are considered as the standard modality, as showing a prolonged survival[8]. The renal artery embolization prior to surgery as adjuvant treatment in nephrectomy has been utilized for more than four decades. Craven et al.[9] reported that the embolization minimized the oozing in nephrectomy, control troublesome hematuria and improved clinical status. Later, several studies showed that the renal embolization reduced bleeding and surgical procedure time in nephrectomy, increasing the ease of dissection through edema tissue[10–12]. The embolization devascularized the tumor and allowed the renal vein to be ligated early, before control of the renal artery, without increasing the risk of tremendous hemorrhage from venous collaterals, which alleviated the nephrectomy in the cases with renal hilar structure invasion. This practice was also proposed to have immunological benefits, including augmentation of the natural killer cell and lymphoproliferative response, triggered by necrosis factor release, which caused the immune response[13–15].
Conversely, there were some conflicting data regarding the utility of the adjuvant renal artery embolization prior to nephrectomy. A study[6] evaluated the 227 renal cancer patients received embolization prior to nephrectomy matched with 607 patients treated with surgery alone. The investigators reported that there were no significant differences between the groups in complications, cancer-specific survival. However, the median follow-up was significantly lower in the surgical group than embolization group. This study showed that the blood transfusion requirements were significantly higher in embolization group. The explanation for that could be the incomplete occlusion of the renal artery, the obstruction of the inferior vena cava leading to hypertension of the bypass veins, which increased the hemorrhage of the venous collaterals around the renal capsule, when mobilizing the kidney and tumor. In Subramanian’s study[7], 231 patients underwent the radical nephrectomy and thrombectomy, of 135 received the pre-operative embolization. It was reported that the patients in embolization group had longer median operative time (390minutes versus 313minutes), received more blood transfusions than the control group (8units versus 4units). The authors pointed out that the embolization was significantly associated with higher mortality (13% versus 3%). This series concluded that the embolization did not show meaningful advantages. However, the embolization group was composed of higher tumor stage, IVC thrombus level, ASA scores, and need for the utility of cardiopulmonary bypass. Besides, the patients received the embolization were almost associated with hilar invasion and lymphadenopathy. These could explain the longer operative time and more transfusion requirements in embolization group.
In our study, we found that there was no significance in operative time between the two groups. One explanation could be that the tumor size in the I-RAE group was larger than that in the Non-RAE group, requiring more time for mobilizing and hemostasis. We also performed the renal artery embolization before laparoscopic surgery. The prophylactic embolization also had some merits in minimal-invasive surgery. Chopra and his colleagues[16] performed the pre-operative embolization in 80% (20/24) patients in Robot-assisted Level II–III IVC Thrombectomy. They concluded that the renal artery embolization decompressed the venous collaterals, decreased blood loss and enhanced robotic efficacy. Wang et al[17] reported that the pre-operative artery embolization could reduce intraoperative oozing, which was helpful for mobilizing the kidney, manipulating the vessels in Robot-assisted Inferior Vena Cava Thrombectomy. The embolization was necessary and critical for left renal cancer, as the thrombectomy was performed in the left decubitus position, it was very difficult to expose the left renal artery. The embolization allowed the left renal vein could be disconnected well before the left renal artery can be robotically secured, intraoperatively.
Several types of materials were available for renal artery embolization, such as metallic coils, gelatin sponge, polyvinyl alcohol, embospheres and N-butyl-2-cyanoacrylate (NBCA). We preferred the gelatin sponge, as it was cheapest. Its embolic effect could last for 2–3 weeks. Besides, it allowed surgical clamping and ligation during the nephrectomy with on hindrance. The most common complaints after embolization were post-infarction syndrome, characterized by nausea, vomiting, fever, flank pain, malaise, hematuria, transient hypertension and hyponatremia. The complications were self-limited and easily controlled with pre-medication and symptomatic treatment. The artery embolization techniques had developed significantly in the past 20 years. Imaging capabilities had improved dramatically. New embolic agents allowed for more effective and precise embolization. These decreased the complications caused by incomplete embolization or embolic material migration. The post-infarction syndrome always occurred in 1 to 3 day after the embolization. For the traditional embolization, the incidence of post-infarction syndrome ranged from 40–90%[18]. Kalman et al[11] reported that the nephrectomy should be performed within 48 hours. It became surgical difficult 3 days after the embolization, as the secondary collateral vessel formation. Minimizing the interval between the RAE and surgery could decrease the post-infarction syndrome. So, in this study, all the patients in I-RAE group underwent surgery within 3 hours after embolization, we didn’t observe any major complications associated with RAE itself. The instant embolization had some advantages over the delayed surgery. First, the instant embolization alleviated the patients’ emotional strain and anxiety of waiting for several days. Second, as the nephrectomy was performed within 3 hours, this minimized the post-infarction syndrome. Some studies reported that if the nephrectomy was performed more than 4 days after the embolization, the mortality may increase due to septic complications[19, 20]. Last, the instant approach reduced the hospitalization and cost compared to the delayed surgery.
To date, as there are no randomized, large-scale, prospective trials, which compare the surgical outcomes of embolization and non-embolization, the European Association of Urology doesn't recommend the embolization as a routine procedure to manage RCC. However, in our study, the devascularizing of tumor reduced the intraoperative blood loss and transfusion, which facilitated the nephrectomy and thrombectomy in local advanced RCC with large size tumor and hilar invasion. The prophylactic embolization could make some non-resectable renal mass resectable, providing the urologists with a reliable option for locally advanced RCC. Besides, as the combination use of target drugs and immuno-check point inhibitor, the patients could benefit from the embolization-facilitated surgery.