Retroperitoneal tumors can be very challenging to manage. Large, single institution case series of retroperitoneal tumors suggest that most are malignant [1
]. For malignant disease (i.e., sarcomas), completeness of resection is a critical prognostic factor for survival [3
]. In fact, a recently proposed revised staging system and a survival nomogram both incorporate completeness of resection [12
]. However, because retroperitoneal tumors are often enormous and close to critical retroperitoneal structures and organs, complete resection is difficult and the potential for perioperative complications is high. The results of our study suggest that for most patients, complete and safe resection is possible, but multi-organ and major vascular resections are frequently required and several adjunct procedures may be utilized to minimize complications.
For retroperitoneal tumors, large case series indicate that multi-organ resection is to be anticipated in up to 80% of patients, with the kidney being the most common organ resected en bloc with the primary tumor [3
]. Although preoperative imaging studies may suggest adjacent organ involvement, often, definitive assessment can only be made intraoperatively. This underscores the importance of preoperative planning, especially if the visceral organs to be resected are outside of the surgeon's area of technical expertise. Assistance from consulting services may be needed.
Recently, Bonvalot et al. have advocated "complete compartmental surgery", which involves multi-organ resection, even without obvious tumor involvement of adjacent organs at the time of surgical exploration [14
]. In a retrospective review of 382 patients undergoing retroperitoneal sarcoma resection, the authors found that this technique was associated with a 3-fold decrease in local recurrence in comparison to standard multi-organ resection only for tumor involvement. However, no difference in survival was noted. Santos et al. found that the technique of compartmental surgery did not appear to impact either recurrence rates or survival and was in fact, associated with higher intraoperative blood transfusion requirements and postoperative morbidity [15
]. We did not utilize complete compartmental surgery in our series and believe that more studies are needed to validate its routine use.
Retroperitoneal tumors can also involve major abdominal vascular structures in up to 18% of patients [16
], necessitating concomitant en bloc resection, as was done in five (8%) of our cases. Preoperative planning is critical and should include consultation with a vascular surgeon for resection and reconstruction. For right-sided tumors, the surgeon must be prepared to resect the inferior vena cava (IVC) when a solid mass abuts it. Most published reports in patients with non-hepatic, non-renal primary retroperitoneal tumors advocate use of synthetic graft (e.g. polytetrafluoroethylene, PTFE) to reconstruct the IVC [16
]. Graft patency rates are very good (90-94%), as shown by studies with 19 to 36 months of follow-up review [16
]. Alternatively, proximal ligation of the IVC after resection may be appropriate in select patients whose infrarenal tumors have extensive venous collateralization, or when concern for bowel anastomotic leakage would make synthetic graft placement risky. Minimal morbidity was reported in 11 patients who had proximal IVC ligation [20
], but a subsequent report found that postoperative leg edema was twice as common after IVC ligation than after graft reconstruction [21
]. Finally, although more rare and arguably more challenging, aortic resection for retroperitoneal tumors has also been described [16
]. A variety of graft materials have been used for aortic resection, including Dacron [16
], PTFE [16
], polyethylene terephthalate [22
], and even autologous superficial femoral vein [23
]. Five patients with aortic resection and prosthetic reconstruction were reported to have a patency rate of 89% at 19 months [16
]. For both venous and arterial reconstruction, the option of using cryopreserved human vein or extra-anatomic bypass (i.e. axillary-femoral) also exist, particularly when there is concern for enteric contamination within the resection site. In select cases, extracorporeal circulatory bypass may be helpful to permit complete and safe resection of retroperitoneal tumors with major vascular involvement [24
In our series, complete resection was feasible for recurrent retroperitoneal tumors, although it was achieved slightly less often than for primary tumors (93% versus 97%, Table ). Even more dramatic differences were reported by Lewis et al. more than a decade ago - 80% of patients with primary disease had complete resection versus 57% for those with local recurrence, and not surprisingly, the rate of complete resection continued to decrease with each subsequent recurrence [3
]. Similar to our findings, more recent studies indicate a difference in the rate of complete resection, but suggest that the difference may not be as dramatic (99% versus 90%) [9
]. The recent higher rates of complete resection for recurrent disease may reflect improved surgical technique, a more aggressive approach to resection of all retroperitoneal tumors, or improved patient selection. Complete resection should always be considered for recurrent disease as it is critical for improved survival [25
] and in fact, may even result in comparable survival to patients after complete resection of primary disease [26
Careful review of preoperative imaging is essential to anticipate potential operative scenarios and determine whether to utilize adjunct procedures to minimize complications. For example, ureteral stent placement and femoral nerve monitoring should be considered to identify these important structures when masses are near to their expected location in the retroperitoneum. Posterior laminotomy should be considered to permit complete resection of retroperitoneal tumors involving spinal nerve roots and when masses abut the vertebral bodies. Preoperative angioembolization of highly vascular tumors should be considered to minimize intraoperative blood loss.
Despite use of adjunct procedures, perioperative complications are common given the magnitude of the operations often required in retroperitoneal tumor resection. In terms of perioperative mortality, our 2% rate compares favorably to the 1-3% rates reported for large single institution patient cohorts [3
] and a recent ACS-NSQIP national database review [27
]. Our complication rate of 16% is also comparable to the recent 13-26% rates reported in the literature [6
]. The caveat of reporting complications, of course, is that they are heavily dependent on the experience and expertise of the surgeon(s) and the resources of the institution, and are to some extent, driven by extent of the operation, which may differ from one patient to another.
Although not performed in our current series, laparoscopic resection of retroperitoneal tumors is emerging as a potential surgical option in select cases. Two recent series have suggested that in benign tumors without adjacent organ or vessel involvement, this approach can be done safely and result in good perioperative outcomes [28
]. Tumor size does not appear to significantly affect blood loss or operative time, although the majority of tumors are relatively small (<10 cm). Laparoscopic resection of retroperitoneal liposarcoma [30
] and leiomyosarcoma [32
] have also been described in case reports. We feel that use of this approach in malignant disease should be tempered by the same oncologic principles of complete and safe resection and that there should be a low threshold for conversion to laparotomy in cases of actual or potential adjacent organ involvement.