Outcome of accelerated radiotherapy alone
or accelerated radiotherapy followed by exenteration
of the nasal cavity in dogs with intranasal neoplasia:
53 cases (1990–2002)
William M. Adams, DVM, DACVR; Dale E. Bjorling, DVM, MS, DACVS; Jonathan F McAnulty, DVM, PhD;
Eric M. Green, DVM, DACVR; Lisa J. Forrest, VMD, DACVR; David M. Vail, DVM, DACVIM
ing 60% in most reports1-4 involving large numbers of
treated dogs. In 1 study,5 exenteration of the nasal cav-
Objective—To compare long-term results of radio- ity alone resulted in a median survival time of < 6
therapy alone versus radiotherapy followed by exen- months, and radiotherapy is currently recognized as
teration of the nasal cavity in dogs with malignant the most effective treatment modality.6-8 A combination
of surgery followed by orthovoltage radiation was
Design—Retrospective study. reported to result in a median survival time of 23
Animals—53 dogs with malignant intranasal neoplasia. months9; however, more recent studies2,10 have not sub-
Procedure—All dogs underwent radiotherapy con- stantiated these results. Megavoltage radiotherapy
sisting of administration of 10 fractions of 4.2 Gy each given soon after exenteration of the nasal cavity does
on consecutive weekdays. For dogs in the surgery not appear to improve survival times in dogs with
group (n = 13), follow-up computed tomography was intranasal neoplasia, compared with megavoltage
performed, and dogs were scheduled for surgery if radiotherapy without surgery.1,3 A higher dosage mega-
persistent or recurrent tumor was seen. voltage radiotherapy protocol has proven unacceptable
Results—Perioperative complications for dogs that for tumors in this site because of severe damage to the
underwent surgery included hemorrhage requiring surrounding unaffected tissues,11 and the use of
transfusion (2 dogs) and subcutaneous emphysema chemotherapy in combination with radiotherapy has
(8). Rhinitis and osteomyelitis-osteonecrosis occurred
significantly more frequently in dogs in the radiother-
met with limited success.12-14
apy and surgery group (9 and 4 dogs, respectively) Previous studies1,2,9,10 of the results of combining
than in dogs in the radiotherapy-only group (4 and 3 radiotherapy and surgery for the treatment of dogs
dogs, respectively). Two- and 3-year survival rates with intranasal neoplasia have involved administration
were 44% and 24%, respectively, for dogs in the of external beam fractionated radiotherapy beginning
radiotherapy group and 69% and 58%, respectively, 14 to 21 days after exenteration of the nasal cavity. To
for dogs in the surgery group. Overall median survival our knowledge, the effectiveness of performing radio-
time for dogs in the radiotherapy and surgery group therapy prior to exenteration of the nasal cavity in dogs
(47 months) was significantly longer than time for with intranasal neoplasia has not been determined.
dogs in the radiotherapy-only group (19.7 months). The purpose of the study reported here, therefore, was
Conclusions and Clinical Relevance—Results sug- to compare clinical outcome for dogs with intranasal
gest that exenteration of the nasal cavity significantly neoplasia treated with radiotherapy alone with out-
prolongs survival time in dogs with intranasal neoplasia come for dogs that underwent exenteration of the nasal
that have undergone radiotherapy. Exenteration after
radiotherapy may increase the risk of chronic complica- cavity ≥ 6 weeks after undergoing radiotherapy.
tions. (J Am Vet Med Assoc 2005;227:936–941)
Criteria for Selection of Cases
Medical records of dogs examined at the University
of Wisconsin Veterinary Medical Teaching Hospital
I n dogs, intranasal neoplasia continues to be a diffi-
cult disease to control, with recurrence rates exceed- between January 1990 and January 2002 because of
intranasal neoplasia were reviewed. Dogs were eligible
From the Departments of Surgical Sciences (Adams, Bjorling, for inclusion in the study if the diagnosis had been con-
McAnulty, Green, Forrest) and Medical Sciences (Vail), School of firmed histologically, the dog had undergone radiother-
Veterinary Medicine, University of Wisconsin, Madison, WI 53706. apy, and follow-up information regarding cause of death
Dr. Green’s present address is Department of Clinical Sciences,
College of Veterinary Medicine, The Ohio State University,
was available in the medical record or through tele-
Columbus, OH 43210. Dr. Vail’s present address is Animal Cancer phone conversations with the owner or referring veteri-
Center, College of Veterinary Medicine and Biomedical Sciences, narian. Dogs were excluded from the study if they had
Colorado State University, Fort Collins, CO 80523. received chemotherapy or immunotherapy before, dur-
Supported by a Companion Animal Grant from the University of ing, or after undergoing radiotherapy.
Presented in part at the annual meeting of the American College of
Veterinary Radiology, Chicago, December 2002.
The authors thank Cheryl Bohling and Joan Capelle for technical In all dogs, computed tomography was performed
assistance and assistance with records management. for purposes of tumor staging and treatment planning.
Address correspondence to Dr. Adams. Biopsy specimens were collected following computed
936 Scientific Reports: Retrospective Study ,
JAVMA, Vol 227 No. 6, September 15, 2005
tomography, and tumors were classified as stage 1, 2, 3, Statistical analyses—Survival curves were gener-
or 4 on the basis of criteria previously reported to be ated by means of the Kaplan-Meier method, which
associated with prognosis following radiotherapy accounted for (ie, censored) dogs that were alive, had
(stage 1 = unilateral disease with no bone destruction; been lost to follow-up, or died of unrelated causes.
stage 2 = bony involvement beyond the turbinates; Effects of treatment group, histologic type, and clini-
stage 3 = orbital, subcutaneous, or submucosal mass; cal stage were examined by use of log-rank tests to
and stage 4 = mass involving the nasopharynx or inva- determine significant differences between curves. The
sion through the cribriform plate).7,a Radiotherapy was Fisher exact test was used to compare signalment data,
initiated within 3 weeks after computed tomography histologic type, clinical stage, recurrence rate, and
and consisted of administration of 10 fractions of complications between treatment groups. Relative risk
4.2 Gy each on consecutive weekdays, beginning on a of developing complications was determined with
Monday. The radiotherapy protocol was planned on standard methods. Age and body weight were com-
the basis of computed tomographic images with a 2- pared between treatment groups with the Mann-
dimensional computer planning system.b The usual Whitney U test. All analyses were performed with
radiotherapy protocol included a lateral and a dorsal standard softwarec; values of P < 0.05 were considered
field with 30o wedges and blocking of the contralateral significant.
eye in the dorsal field. Occasionally, the protocol
included a ventral or opposite lateral field. Results
Prior to 1998, surgery was not offered as part of Fifty-three dogs met the criteria for inclusion in
the treatment protocol for dogs with intranasal neopla- the study. Forty dogs underwent radiotherapy alone.
sia. Beginning in 1998, owners of dogs with intranasal Twenty-three of these dogs had been examined and
neoplasia were offered a financial incentive consisting treated prior to 1998, when surgery was not offered for
of subsidized computed tomography if they agreed to treatment of intranasal neoplasia, and 17 were exam-
allow surgical removal of persistent tumor observed on ined and treated after 1998, but their owners declined
follow-up nasal computed tomography. For dogs surgery. Owners of the remaining 13 dogs agreed to
whose owners agreed to adjuvant surgery, follow-up allow surgical removal of any persistent tumor
nasal computed tomography was scheduled for 6 observed on follow-up nasal computed tomography.
weeks after radiotherapy was completed. If tumor All 13 dogs returned for follow-up computed tomogra-
regression was judged to be ≥ 80% on the follow-up phy, and 11 eventually underwent exenteration of the
computed tomogram, an additional subsidized com- nasal cavity. The remaining 2 dogs did not undergo
puted tomographic examination was scheduled for 6 exenteration because tumors were considered to be
weeks later. If tumor regression was < 80% or recur- inoperable at the time of follow-up computed tomog-
rence or progression of the tumor was suspected at the raphy. However, data for these 2 dogs were included
time of the additional computed tomographic exami- with data for the 11 dogs that underwent surgery to
nation, nasal exenteration was performed and tissues diminish the possibility of selection bias in statistical
were submitted for histologic examination. analyses (ie, intent-to-treat analyses).
Exenteration was performed through a dorsal
Pretreatment findings—Pretreatment body weight
rhinotomy as described.15 In brief, the nasal cavity was
was not significantly different between treatment
entered by means of a dorsal midline approach during
groups (Table 1); however, dogs in the radiotherapy
which a flap of bone was created to expose the nasal
group were significantly (P = 0.024) older than dogs in
turbinates and nasal cavity. The turbinates and periosteal
the radiotherapy and surgery group. Sex, clinical stage,
tissue lining the nasal cavity were extirpated, and hemo-
and histologic-type distributions were not significantly
stasis was established by means of gauze pressure pack-
different between groups.
ing and cautery. After excision of all tissue in the nasal
cavity, the subcutaneous tissue and skin were closed in a Radiotherapy and surgery group—For the 13
routine manner. In some dogs, cotton umbilical tape was dogs in the radiotherapy and surgery group, the initial
placed in the nasal cavity and exited through the nares follow-up examination was performed 6 to 10 weeks
to maintain postoperative hemostasis. This packing was after completion of radiotherapy. Four of the 13 had a
removed on the day after surgery. In 1 dog, the nasal ≥ 80% reduction in tumor volume, as determined by
bone flap was replaced and secured with interrupted means of computed tomography, and 4 others had a
sutures through holes drilled in the flap and maxilla. In 50% to 70% reduction in tumor volume. The remain-
the other dogs, the bone flap was discarded. ing 5 dogs had a < 50% reduction in tumor volume. Of
Follow-up examinations were continued at 2- to the 2 dogs with evidence of cribriform plate involve-
3-month intervals until 1 year after surgery and then at ment prior to radiotherapy, 1 had a 60% to 70% reduc-
6-month intervals until death. Complications associat- tion in tumor size 7.5 weeks after completion of radio-
ed with radiotherapy or surgery were recorded at the therapy and the other had a < 50% reduction in tumor
time of each follow-up examination. size 10 weeks after completion of radiotherapy. Both
For dogs included in the study, the following had evidence of recalcification of the cribriform plate.
information was obtained from the medical records: For the 11 dogs that underwent surgery, median
signalment, tumor type, tumor stage, radiotherapy and time to surgery following completion of radiotherapy
surgery details, other treatments administered, periop- was 10 weeks (range, 6 to 73 weeks), with 10 of the 11
erative complications, recurrent and late complica- dogs having surgery by 14 weeks after radiotherapy
tions, and overall survival time. was completed. In 8 dogs, surgery was performed
JAVMA, Vol 227 No. 6, September 15, 2005 Scientific Reports: Retrospective Study 937
Table 1⎯Signalment, clinical stage, and histologic type for dogs unrelated causes 29 months after radiotherapy was
with intranasal neoplasia enrolled in a study comparing outcome completed. Two dogs developed persistent nasal
of radiotherapy alone with outcome of radiotherapy followed by
exenteration of the nasal cavity. aspergillosis that was partially controlled for 30
months with intermittent administration of itracona-
Radiotherapy Radiotherapy zole; tumor recurrence was documented in both dogs.
alone and surgery Two dogs in the radiotherapy and surgery group
Variable (n = 40) (13) P value
that had had extensive tumor-related bone destruction
Body weight (kg) 26.2 (6.0–42.6) 25.6 (5.3–38.0) 0.840 prior to undergoing radiotherapy developed shortening
Male 18 (45) 6 (46) of the maxilla, resulting in a brachycephalic appear-
Female 22 (55) 7 (54) ance. One of those dogs developed an osteosarcoma of
Age (y) 11.3 (2.7–14.7) 7.6 (5.9–12.0) 0.024 the maxilla 5 years after undergoing radiotherapy.
1 8 (20) 2 (15) 0.999 Dogs in the radiotherapy-only group were not
2 13 (33) 3 (23) 0.740 administered antimicrobials following radiotherapy.
3 5 (12) 4 (31) 0.200 Four dogs in that group developed chronic rhinitis after
4 14 (35) 4 (31) 0.999
Histologic type 0.690 treatment. In 3 of the 4, rhinitis was associated with
Carcinoma 9 (23) 3 (23) osteonecrosis. Two of those dogs developed oronasal
Adenocarcinoma 12 (30) 3 (23) fistulas at 5 and 9 months after radiotherapy. The one
Anaplastic carcinoma 12 (30) 2 (15) that had the fistula at 5 months underwent 3 attempts
Squamous cell 0 (0) 2 (15)
carcinoma at surgical repair, but a small fistula persisted at the time
Chondrosarcoma 4 (10) 1 (8) of euthanasia 31 months after radiotherapy. No tumor
Osteosarcoma 0 (0) 1 (8) recurrence was suspected. The other dog with an
Soft tissue sarcoma 3 (7) 1 (8)
oronasal fistula had 2 surgeries for bone debridement
Data are given as median (range) or number (percentage). and dental extraction and had a persistent fistula at the
time tumor recurrence was documented 21 months
because of persistent residual tumor seen on the initial after radiotherapy. That dog was euthanatized 4 months
follow-up computed tomograms obtained 6 to 10 later. The third dog developed a nasocutaneous fistula
weeks after radiotherapy was completed (50% to 90% near the medial canthus of 1 eye at 23 months after
tumor reduction). In 2 dogs, surgery was performed radiotherapy. Despite 3 months of treatment with
because a persistent or progressive tumor was seen on trimethoprim-sulfonamide for a susceptible hemolytic
a second follow-up computed tomogram obtained Streptococcus sp, the fistula was still draining 5 months
between 10 and 13 weeks after radiotherapy. In the later when the dog died. The referring veterinarian
remaining dog, 8 follow-up computed tomograms were thought that extensive maxillary osteonecrosis con-
obtained before tumor recurrence was identified; that tributed to that dog’s death. No tumor recurrence was
dog underwent exenteration 73 weeks after radiother- suspected on the basis of computed tomographic find-
apy was completed. ings. The dog that developed chronic rhinitis was given
For dogs that underwent surgery, perioperative multiple courses of ampicillin between 1 and 9 months
complications included epistaxis necessitating blood after radiotherapy. Improvement was noted during peri-
transfusion (2 dogs) and self-limiting subcutaneous ods of antimicrobial treatment, but signs recurred when
emphysema (8). Surgical removal of the grossly visible medication was discontinued. Rhinitis and recurrent
tumor was incomplete in 1 dog because of brain tumor with pulmonary metastasis were identified at
involvement; this dog was euthanatized 8 days after necropsy 9 months after radiotherapy was completed.
surgery because of complications. Three dogs in the radiotherapy and surgery group
In 9 of the 11 dogs, results of histologic examination eventually lost sight in the eye included in the radia-
of biopsy specimens obtained at the time of nasal cavity tion field. Of these, 1 required enucleation 22 months
exenteration were positive for tumor cells. In the remain- after radiotherapy was completed because of glaucoma.
ing 2 dogs, only inflammatory changes were seen. Twelve dogs in the radiotherapy-only group lost sight
in 1 (8 dogs) or both (4) eyes following radiotherapy.
Complications—Nine of the 13 dogs in the radio- Of these, 3 underwent enucleation because of
therapy and surgery group developed rhinitis. Four of descemetoceles or keratoconjunctivitis sicca.
these dogs had a single episode of rhinitis after under- Dogs in the radiotherapy and surgery group were
going nasal cavity exenteration; in all 4, the rhinitis significantly more likely to develop rhinitis (relative
was responsive to treatment with amoxicillin or amox- risk, 3.17; 95% confidence interval, 1.40 to 7.17) or
icillin-clavulanic acid. Five other dogs in this group osteomyelitis-osteonecrosis (relative risk, 5.13; 95%
developed chronic or recurrent rhinitis that progressed confidence interval, 1.40 to 18.6) than were dogs in the
to osteomyelitis with or without bone necrosis and radiotherapy-only group. The risk of blindness was not
persisted for 4 to 29 months. These dogs were treated significantly higher for dogs in the radiotherapy-only
with a variety of antimicrobials, including amoxicillin- group (relative risk, 1.30; 95% confidence interval,
clavulanic acid, enrofloxacin, cephalexin, doxycycline, 0.43 to 3.91) than for dogs in the radiotherapy and
and metronidazole. One of these 5 dogs developed surgery group.
rhinitis associated with an antimicrobial-resistant Two dogs in the radiotherapy and surgery group
Staphylococcus sp and required surgical debridement. and 1 in the radiotherapy-only group developed dental
That dog developed a permanent nasocutaneous fistu- caries and evidence of death of the pulp of teeth in the
la, and chronic mild rhinitis persisted until it died of radiation field that necessitated fillings, extractions,
938 Scientific Reports: Retrospective Study ,
JAVMA, Vol 227 No. 6, September 15, 2005
and root canal procedures 2.5 to 4 years after radio- The rate of local recurrence of intranasal neoplasia
therapy. Numbers of dogs in each group that developed for dogs in the radiotherapy-only group (68%) was not
these complications were too small to allow for statis- significantly different from the rate for dogs in the
tical analysis. radiotherapy and surgery group (60%) that have died.
Metastasis to the regional lymph nodes or lungs was
Outcome—Analysis of censored survival curves documented in 4 of the 40 (10%) dogs in the radio-
indicated that 68%, 44%, 24%, and 12% of dogs in the therapy-only group following radiotherapy; metastasis
radiotherapy-only group were alive 1, 2, 3, and 4 years, was not observed in any of the dogs in the radiothera-
respectively, after completion of radiotherapy, com- py and surgery group.
pared with 77%, 69%, 58%, and 46%, respectively, of For the 40 dogs in the radiotherapy-only group,
dogs in the radiotherapy and surgery group. Median median overall survival time for dogs with a carcinoma
survival time for dogs in the radiotherapy-only group (21.6 months) was not significantly (P = 0.603) differ-
(19.7 months) was significantly (P = 0.022) shorter ent from median overall survival time for dogs with a
than median survival time for dogs in the radiotherapy sarcoma (18.3 months). No significant (P = 0.669) dif-
and surgery group (47.7 months; Figure 1), even after ferences in median overall survival times were detect-
controlling for age. ed among groups when the 40 dogs were grouped on
Twenty-six of the 40 (65%) dogs in the radiothera- the basis of clinical stage prior to radiotherapy (stage 1,
py-only group had local recurrence of intranasal neopla- 25 months; stage 2, 21.6 months; stage 3, 11.6 months;
sia without evidence of metastasis. Nine of the 26 (35%) and stage 4, 18.3 months). Similarly, median survival
dogs that underwent radiotherapy alone and had evi- time for dogs classified as stage 1 or 2 prior to radio-
dence of recurrence of intranasal neoplasia without evi- therapy was not significantly (P = 0.18) different from
dence of metastases were euthanatized within 10 months median survival time for dogs classified as stage 3 or 4.
after completion of radiotherapy because of progressive
disease. Between 10 and 19 months following radiother-
apy, 7 more succumbed to progressive local disease;
In dogs with intranasal neoplasia, the condition is
between 20 and 29 months, another 3 succumbed to
generally advanced by the time of referral to a special-
local disease; and between 30 and 51 months, 4 more
ty center or teaching hospital and is not eliminated by
succumbed to local disease. Two others were euthana-
curative-intent radiotherapy in 60% to 80% of
tized because of metastasis < 9 months after radiothera-
dogs.3,4,7,16 This coincides with findings in the present
py was completed, and 1 was euthanatized because of
metastasis 31 months after radiotherapy was completed. study, in that tumor was identified histologically in 9 of
Of the remaining 11 dogs, 9 died or were euthanatized 11 dogs that underwent surgery between 6 and 73
for unrelated disease 1 to 65 months after radiotherapy weeks after completion of radiotherapy.
and 2 remained alive without evidence of recurrence 34 Reported median survival times for dogs with
and 47 months after radiotherapy. intranasal neoplasia treated with megavoltage radiother-
Six of the 13 dogs in the radiotherapy and surgery apy alone ranged from 8 to 14 months.3,4,16,17 In the pre-
group had local recurrence of intranasal neoplasia 3 to sent study, median survival time for the 40 dogs that
48 months after treatment, including both dogs that did underwent radiotherapy without surgery, chemotherapy,
not undergo surgery. Of the remaining 7 dogs, 4 died or or immunotherapy was 19.7 months. However, 68% of
were euthanatized for an unrelated cause 29 to 68 the dogs that underwent radiotherapy alone were eutha-
months after radiotherapy and 3 were alive without evi- natized because of recurrence of clinical signs indicative
dence of recurrence 30 to 57 months after radiotherapy. or suggestive of local tumor regrowth.
Tumors that have undergone radiotherapy may
express early local recurrence. In this study, 33% of dogs
in the radiotherapy-only group were euthanatized within
10 months of radiotherapy because of local recurrence.
We theorized prior to initiation of the present study that
resection of residual tumor following radiotherapy might
eliminate or delay early recurrence following radiothera-
py; this was the reason we began offering surgery to own-
ers of dogs with evidence of persistent or recurrent disease
following radiotherapy. Although overall local tumor
recurrence rates were not significantly different between
treatment groups, 3-year survival rates for the radiothera-
py and surgery group and the radiotherapy-only group
were 58% and 24%, respectively. Also, 3 of the dogs in the
radiotherapy and surgery group were alive without evi-
dence of disease 30, 55, and 57 months after radiothera-
py was completed. Importantly, results of the present
study indicate that intranasal tumors may recur years after
treatment as evidenced by 2 dogs in the radiotherapy-only
Figure 1—Kaplan-Meier graph of outcome of dogs with intranasal group and 1 dog in the radiotherapy and surgery group
neoplasia enrolled in a study comparing outcome of radiotherapy
(RT) alone with outcome of RT followed by exenteration of the that were euthanatized between 46 and 51 months after
nasal cavity. radiotherapy because of local recurrence.
JAVMA, Vol 227 No. 6, September 15, 2005 Scientific Reports: Retrospective Study 939
In the present study, dogs that underwent nasal we also did not find any difference in survival time
cavity exenteration following radiotherapy had a sub- between groups when dogs were grouped on the basis
stantial risk of developing postoperative complica- of histologic type.
tions. In particular, the risks of developing chronic or Age of the dog at the time of radiotherapy has pre-
recurrent rhinitis and osteomyelitis were significantly viously been suggested to be associated with outcome
higher for dogs in this group than for dogs that under- in dogs with intranasal neoplasia.3 Although median
went radiotherapy alone. Although these complica- age of dogs in the radiotherapy and surgery group in
tions did not appear to affect outcome, chronic bacter- the present study was significantly less than median
ial or fungal rhinitis resulted in long-term management age of dogs in the radiotherapy-only group, we did not
responsibilities for the owners. During exenteration, identify any effect of age on overall survival time in the
all nasal cavity tissue, including the periosteum lining present study.
the nasal cavity, is removed. Healing occurs by forma- Whether there is any relationship between clinical
tion of granulation tissue over the bone and subse- stage and outcome in dogs with intranasal neoplasia is
quent epithelialization. A chronic nasal discharge is also controversial.3,4,7 In a previous studya that used the
common in dogs that undergo nasal cavity exentera- same radiotherapy protocol used in the present study,
tion (without radiotherapy) but commonly resolves clinical stage was significantly associated with survival
within a few months after surgery, although a serous or time. In the present study, however, no significant dif-
purulent discharge may persist.18 In dogs that undergo ference in survival time was found among groups when
radiotherapy prior to nasal cavity exenteration, howev- dogs that underwent radiotherapy alone were grouped
er, the compromised blood supply in the underlying on the basis of pretreatment clinical stage.
bone could impair healing of the exposed bone sur- For dogs in the present study, the time between
faces, resulting in poorly vascularized granulation tis- radiotherapy and nasal cavity exenteration was deter-
sue that is susceptible to opportunistic infection. One mined for individual dogs on the basis of results of fol-
approach that might help to reduce this problem would low-up computed tomography. However, the specifici-
be to resect turbinates only in the area of any persistent ty of computed tomography for identifying viable
or recurrent tumor. However, this presents a challenge tumor following radiotherapy must be in question.
because it can be difficult to identify the margins of a Two dogs in the present study that had a 50% to 70%
nasal tumor in the presence of substantial exudate and reduction in tumor volume on computed tomograms
grossly abnormal, but nonneoplastic, turbinate tissue. obtained 6 weeks after radiotherapy had no histologic
In such a situation, it may be advisable to preserve the evidence of tumor at the time of surgery and died of
periosteal lining of the nasal cavity as much as possible unrelated causes 28.5 and 52 months after undergoing
to minimize compromise of the blood supply to the radiotherapy. Conversely, a dog that had an 80% to
bone surfaces. This approach may better preserve local 90% reduction in tumor volume on a computed tomo-
defenses against opportunistic infection and reduce the gram obtained 11 weeks after radiotherapy had histo-
incidence of postsurgical rhinitis and osteomyelitis. We logic evidence of viable tumor cells at the time of
currently recommend long-term (months) treatment surgery. The most accurate means of documenting per-
with broad-spectrum antimicrobials (typically amoxi- sistent viable tumor is probably comparison of serial
cillin-clavulanic acid) to reduce the incidence and computed tomograms or magnetic resonance images
severity of bacterial rhinitis in dogs undergoing nasal for evidence of progressive disease. The use of positron
cavity exenteration following radiotherapy. emission tomography would theoretically also be a
An unexpected late effect observed in the present means of determining viability of suspected persistent
study was the development of caries and dental pulp tumor; however, documentation of progressive disease
death between 2.5 and 4 years after radiotherapy. Tooth on serial imaging studies is still the most accurate
death and xerostomia-induced caries are well-recog- means of identifying residual tumor.
nized late complications following radiotherapy of oral Limitations of the present study include the small
and maxillary neoplasms in human patients.19-22 The number of dogs in the radiotherapy and surgery group
paucity of information regarding this complication in and the lack of consistent follow-up computed tomogra-
dogs may be attributable to limited information con- phy for dogs in the radiotherapy-only group, which pre-
cerning long-term outcome of dogs that have under- cluded an accurate determination of the time to local
gone radiotherapy of tumors of the head. recurrence. The finding in the present study that survival
Results of previous studies3,17 suggest that doses com- time was longer in dogs that underwent surgery will
monly used for megavoltage radiotherapy of intranasal require verification with a randomized controlled trial in
neoplasia in dogs are inadequate. However, increasing the which groups undergo identical follow-up. Despite these
radiation dose or using a radiation sensitizer can lead to limitations, the longer survival time for dogs in the radio-
severe acute mucositis, ocular inflammation, or skin therapy and surgery group in the present study suggests
necrosis and therefore may not be advisable.11,23 Use of that further application and evaluation of this treatment
surgery following completion of radiotherapy, as strategy for intranasal neoplasia are warranted.
described in the present report, appears to offer a viable
alternative. a. Green EM, Adams WM, Forrest LJ, et al. Accelerated RT for canine
The relationship, if any, between histologic type nasal neoplasia (abstr). Vet Radiol Ultrasound 2003;44:113.
and outcome for dogs with intranasal neoplasia is con- b. Prowess 3000 Radiotherapy Treatment Planning System, SGGI,
troversial1,2,4; however, recent reports3,7,10 have not sub- c. Prism 4, GraphPad Software, San Diego, Calif.
stantiated any such relationship. In the present study,
940 Scientific Reports: Retrospective Study ,
JAVMA, Vol 227 No. 6, September 15, 2005
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