Discussion
Hemipelvectomy is a complex procedure that requires extensive surgical planning, adherence to surgical oncology techniques, and thorough familiarity with regional anatomy.1 There is inherent concern for hemorrhage due to the transection of large muscle groups and presence of major vessels. Although an external hemipelvectomy can be performed, an internal pelvectomy can be an alternative for pelvic tumors resections and result in a favorable clinical outcome.4 Internal hemipelvectomy may alter the weight bearing axis of the contralateral hemipelvis resulting in fractures.22 The decision regarding which surgery is appropriate should depend on the owner’s goals, the surgeons experience, comorbidities, extent of neoplasia, presence of metastasis, and ability to pursue adjuvant radiation therapy.
In the present literature the general precedents are that an internal hemipelvectomy should only be considered when tumor resection and margins can be achieved as well as a functional limb.6Canine appendicular CSA is often treated effectively with limb amputation. In contrast, pelvic CSA margins are not always achievable.26 Chondrosarcomas, due to their generally poor vascularity and low rate of mitosis (as in this case), can have an inherent resistance to chemotherapy and radiation therapy.27 Radiation therapy is considered for chondrosarcomas if a tumor is deemed non-surgical or incomplete margins are achieved.27 In some human reports, greater than 60 Gy of radiation was required for local disease control.15,27 The dog in this case report received nineteen three Gy fractions for a total of 57 Gy over the course of a month with no evidence of local recurrence. The dog presumably succumbed to an unrelated disease 1271 days later. This dog’s survival time was similar to the median survival time previously described for pelvic CSA.17 Likewise, ischiectomy with limb preservation for an ischial chondrosarcoma in an 11-year-old FS mixed breed dog provided a satisfactory clinical outcome with no evidence of local recurrence or metastatic spread over 500 day postoperative period.2
In a retrospective study of long-term outcomes for dogs and cats after hemipelvectomy for surgical excision of a variety of tumor types, almost a third of cases had incomplete margins (dogs: 29/84; cats: 4/16; 100 cases total) with local tumor occurrence occurring in 16% and 12.5% of dogs and cats respectively. Six dogs out of nine, had CSA with incomplete margins, four (66%) of which developed metastases and two (33%) deaths were related to the tumor. Regardless of surgical margins, one (11%) had local recurrence and five (56%) had metastatic disease.17 In human medicine (n=67), patients with chondrosarcoma of the pelvis that were treated with definitive surgery 28% developed local recurrence and 36% developed distant metastasis; a high histologic grade was predictive for recurrence (p=0.005).11 Grading chondrosarcoma is prognostic for humans and is based primarily on cellularity and cellular atypia. However, grading chondrosarcomas in dogs is not routinely performed. Grading systems for skeletal chondrosarcomas based on histologic features of malignancy and mitotic count have been described and correlated with prognosis in 35 dogs and 31 dogs.23–25 These histologic features of this case were consistent with an intermediate grade (Grade II) using the criteria of the studies previous mentioned.
Post-operative complications following hemipelvectomy in dogs and cats are generally minor but can include seroma, wound complications (infection at the surgery or incision site, dehiscence, discharge, incisional hernia, etc.), fecal or urinary incontinence, fecal obstipation, pressure sores, and reoccurrence.4,17 In this case, secondary fracture of the left pubis and ischium were appreciated approximately thirty days postoperatively and were presumed to have occurred due to increased weight bearing of the contralateral side. These fractures went on to heal without incident. Implant associated infection occurred eighteen months postoperatively and resolved with prolene mesh removal.
The main purpose of this paper was to document the long-term outcome of an internal cranial hemipelvectomy for a chondrosarcoma of the pelvis. The good outcome in this case study may help veterinarians considering a limb-sparing iliectomy over external hemipelvectomy.19