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