Outcome of accelerated radiotherapy alone or accelerated radiotherapy followed by exenteration of the nasal cavity in dogs with intranasal neoplasia: 53 cases (1990-2002).

Abstract

To compare long-term results of radiotherapy alone versus radiotherapy followed by exenteration of the nasal cavity in dogs with malignant intranasal neoplasia.
Retrospective study.
53 dogs with malignant intranasal neoplasia.
All dogs underwent radiotherapy consisting of administration of 10 fractions of 4.2 Gy each on consecutive weekdays. For dogs in the surgery group (n=13), follow-up computed tomography was performed, and dogs were scheduled for surgery if persistent or recurrent tumor was seen.
Perioperative complications for dogs that underwent surgery included hemorrhage requiring transfusion (2 dogs) and subcutaneous emphysema (8). Rhinitis and osteomyelitis-osteonecrosis occurred significantly more frequently in dogs in the radiotherapy and surgery group (9 and 4 dogs, respectively) than in dogs in the radiotherapy-only group (4 and 3 dogs, respectively). Two- and 3-year survival rates were 44% and 24%, respectively, for dogs in the radiotherapy group and 69% and 58%, respectively, for dogs in the surgery group. Overall median survival time for dogs in the radiotherapy and surgery group (477 months) was significantly longer than time for dogs in the radiotherapy-only group (19.7 months).
Results suggest that exenteration of the nasal cavity significantly prolongs survival time in dogs with intranasal neoplasia that have undergone radiotherapy. Exenteration after radiotherapy may increase the risk of chronic complications.

Full text

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936Scientific Reports: Retrospective Study JAVMA, Vol 227 , No. 6, September 15, 2005
SMALL ANIMALS/
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I
n dogs, intranasal neoplasia continues to be a diffi-
cult disease to control, with recurrence rates exceed-
ing 60% in most reports1-4involving large numbers of
treated dogs. In 1 study,5exenteration of the nasal cav-
ity alone resulted in a median survival time of < 6
months, and radiotherapy is currently recognized as
the most effective treatment modality.6-8A combination
of surgery followed by orthovoltage radiation was
reported to result in a median survival time of 23
months9; however, more recent studies2,10have not sub-
stantiated these results. Megavoltage radiotherapy
given soon after exenteration of the nasal cavity does
not appear to improve survival times in dogs with
intranasal neoplasia, compared with megavoltage
radiotherapy without surgery.1,3 A higher dosage mega-
voltage radiotherapy protocol has proven unacceptable
for tumors in this site because of severe damage to the
surrounding unaffected tissues,11and the use of
chemotherapy in combination with radiotherapy has
met with limited success.12-14
Previous studies1,2,9,10of the results of combining
radiotherapy and surgery for the treatment of dogs
with intranasal neoplasia have involved administration
of external beam fractionated radiotherapy beginning
14 to 21 days after exenteration of the nasal cavity. To
our knowledge, the effectiveness of performing radio-
therapy prior to exenteration of the nasal cavity in dogs
with intranasal neoplasia has not been determined.
The purpose of the study reported here, therefore, was
to compare clinical outcome for dogs with intranasal
neoplasia treated with radiotherapy alone with out-
come for dogs that underwent exenteration of the nasal
cavity ≥ 6 weeks after undergoing radiotherapy.
Criteria for Selection of Cases
Medical records of dogs examined at the University
of Wisconsin Veterinary Medical Teaching Hospital
between January 1990 and January 2002 because of
intranasal neoplasia were reviewed. Dogs were eligible
for inclusion in the study if the diagnosis had been con-
firmed histologically, the dog had undergone radiother-
apy, and follow-up information regarding cause of death
was available in the medical record or through tele-
phone conversations with the owner or referring veteri-
narian. Dogs were excluded from the study if they had
received chemotherapy or immunotherapy before, dur-
ing, or after undergoing radiotherapy.
Procedures
In all dogs, computed tomography was performed
for purposes of tumor staging and treatment planning.
Biopsy specimens were collected following computed
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
Objective—To compare long-term results of radio-
therapy alone versus radiotherapy followed by exen-
teration of the nasal cavity in dogs with malignant
intranasal neoplasia.
Design—Retrospective study.
Animals—53 dogs with malignant intranasal neoplasia.
Procedure—All dogs underwent radiotherapy con-
sisting of administration of 10 fractions of 4.2 Gy each
on consecutive weekdays. For dogs in the surgery
group (n = 13), follow-up computed tomography was
performed, and dogs were scheduled for surgery if
persistent or recurrent tumor was seen.
Results—Perioperative complications for dogs that
underwent surgery included hemorrhage requiring
transfusion (2 dogs) and subcutaneous emphysema
(8). Rhinitis and osteomyelitis-osteonecrosis occurred
significantly more frequently in dogs in the radiother-
apy and surgery group (9 and 4 dogs, respectively)
than in dogs in the radiotherapy-only group (4 and 3
dogs, respectively). Two- and 3-year survival rates
were 44% and 24%, respectively, for dogs in the
radiotherapy group and 69% and 58%, respectively,
for dogs in the surgery group. Overall median survival
time for dogs in the radiotherapy and surgery group
(47 .7 months) was significantly longer than time for
dogs in the radiotherapy-only group (19.7 months).
Conclusions and Clinical Relevance—Results sug-
gest that exenteration of the nasal cavity significantly
prolongs survival time in dogs with intranasal neoplasia
that have undergone radiotherapy. Exenteration after
radiotherapy may increase the risk of chronic complica-
tions. (J Am Vet Med Assoc 2005;227:936–941)
From the Departments of Surgical Sciences (Adams, Bjorling,
McAnulty, Green, Forrest) and Medical Sciences (Vail), School of
Veterinary Medicine, University of Wisconsin, Madison, WI 53706.
Dr. Green’s present address is Department of Clinical Sciences,
College of Veterinary Medicine, The Ohio State University,
Columbus, OH 43210. Dr. Vail’s present address is Animal Cancer
Center, College of Veterinary Medicine and Biomedical Sciences,
Colorado State University, Fort Collins, CO 80523.
Supported by a Companion Animal Grant from the University of
Wisconsin.
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
assistance and assistance with records management.
Address correspondence to Dr. Adams.

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JAVMA, Vol 227 , No. 6, September 15, 2005Scientific Reports: Retrospective Study937
SMALL ANIMALS/
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tomography, and tumors were classified as stage 1, 2, 3,
or 4 on the basis of criteria previously reported to be
associated with prognosis following radiotherapy
(stage 1 = unilateral disease with no bone destruction;
stage 2 = bony involvement beyond the turbinates;
stage 3 = orbital, subcutaneous, or submucosal mass;
and stage 4 = mass involving the nasopharynx or inva-
sion through the cribriform plate).7,aRadiotherapy was
initiated within 3 weeks after computed tomography
and consisted of administration of 10 fractions of
4.2 Gy each on consecutive weekdays, beginning on a
Monday. The radiotherapy protocol was planned on
the basis of computed tomographic images with a 2-
dimensional computer planning system.bThe usual
radiotherapy protocol included a lateral and a dorsal
field with 30owedges and blocking of the contralateral
eye in the dorsal field. Occasionally, the protocol
included a ventral or opposite lateral field.
Prior to 1998, surgery was not offered as part of
the treatment protocol for dogs with intranasal neopla-
sia. Beginning in 1998, owners of dogs with intranasal
neoplasia were offered a financial incentive consisting
of subsidized computed tomography if they agreed to
allow surgical removal of persistent tumor observed on
follow-up nasal computed tomography. For dogs
whose owners agreed to adjuvant surgery, follow-up
nasal computed tomography was scheduled for 6
weeks after radiotherapy was completed. If tumor
regression was judged to be ≥ 80% on the follow-up
computed tomogram, an additional subsidized com-
puted tomographic examination was scheduled for 6
weeks later. If tumor regression was < 80% or recur-
rence or progression of the tumor was suspected at the
time of the additional computed tomographic exami-
nation, nasal exenteration was performed and tissues
were submitted for histologic examination.
Exenteration was performed through a dorsal
rhinotomy as described.15In brief, the nasal cavity was
entered by means of a dorsal midline approach during
which a flap of bone was created to expose the nasal
turbinates and nasal cavity. The turbinates and periosteal
tissue lining the nasal cavity were extirpated, and hemo-
stasis was established by means of gauze pressure pack-
ing and cautery. After excision of all tissue in the nasal
cavity, the subcutaneous tissue and skin were closed in a
routine manner. In some dogs, cotton umbilical tape was
placed in the nasal cavity and exited through the nares
to maintain postoperative hemostasis. This packing was
removed on the day after surgery. In 1 dog, the nasal
bone flap was replaced and secured with interrupted
sutures through holes drilled in the flap and maxilla. In
the other dogs, the bone flap was discarded.
Follow-up examinations were continued at 2- to
3-month intervals until 1 year after surgery and then at
6-month intervals until death. Complications associat-
ed with radiotherapy or surgery were recorded at the
time of each follow-up examination.
For dogs included in the study, the following
information was obtained from the medical records:
signalment, tumor type, tumor stage, radiotherapy and
surgery details, other treatments administered, periop-
erative complications, recurrent and late complica-
tions, and overall survival time.
Statistical analyses—Survival curves were gener-
ated by means of the Kaplan-Meier method, which
accounted for (ie, censored) dogs that were alive, had
been lost to follow-up, or died of unrelated causes.
Effects of treatment group, histologic type, and clini-
cal stage were examined by use of log-rank tests to
determine significant differences between curves. The
Fisher exact test was used to compare signalment data,
histologic type, clinical stage, recurrence rate, and
complications between treatment groups. Relative risk
of developing complications was determined with
standard methods. Age and body weight were com-
pared between treatment groups with the Mann-
Whitney U test. All analyses were performed with
standard softwarec; values of P < 0.05 were considered
significant.
Results
Fifty-three dogs met the criteria for inclusion in
the study. Forty dogs underwent radiotherapy alone.
Twenty-three of these dogs had been examined and
treated prior to 1998, when surgery was not offered for
treatment of intranasal neoplasia, and 17 were exam-
ined and treated after 1998, but their owners declined
surgery. Owners of the remaining 13 dogs agreed to
allow surgical removal of any persistent tumor
observed on follow-up nasal computed tomography.
All 13 dogs returned for follow-up computed tomogra-
phy, and 11 eventually underwent exenteration of the
nasal cavity. The remaining 2 dogs did not undergo
exenteration because tumors were considered to be
inoperable at the time of follow-up computed tomog-
raphy. However, data for these 2 dogs were included
with data for the 11 dogs that underwent surgery to
diminish the possibility of selection bias in statistical
analyses (ie, intent-to-treat analyses).
Pretreatment findings—Pretreatment body weight
was not significantly different between treatment
groups (Table 1); however, dogs in the radiotherapy
group were significantly (P = 0.024) older than dogs in
the radiotherapy and surgery group. Sex, clinical stage,
and histologic-type distributions were not significantly
different between groups.
Radiotherapy and surgery group—For the 13
dogs in the radiotherapy and surgery group, the initial
follow-up examination was performed 6 to 10 weeks
after completion of radiotherapy. Four of the 13 had a
≥ 80% reduction in tumor volume, as determined by
means of computed tomography, and 4 others had a
50% to 70% reduction in tumor volume. The remain-
ing 5 dogs had a < 50% reduction in tumor volume. Of
the 2 dogs with evidence of cribriform plate involve-
ment prior to radiotherapy, 1 had a 60% to 70% reduc-
tion in tumor size 7.5 weeks after completion of radio-
therapy and the other had a < 50% reduction in tumor
size 10 weeks after completion of radiotherapy. Both
had evidence of recalcification of the cribriform plate.
For the 11 dogs that underwent surgery, median
time to surgery following completion of radiotherapy
was 10 weeks (range, 6 to 73 weeks), with 10 of the 11
dogs having surgery by 14 weeks after radiotherapy
was completed. In 8 dogs, surgery was performed

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SMALL ANIMALS/
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because of persistent residual tumor seen on the initial
follow-up computed tomograms obtained 6 to 10
weeks after radiotherapy was completed (50% to 90%
tumor reduction). In 2 dogs, surgery was performed
because a persistent or progressive tumor was seen on
a second follow-up computed tomogram obtained
between 10 and 13 weeks after radiotherapy. In the
remaining dog, 8 follow-up computed tomograms were
obtained before tumor recurrence was identified; that
dog underwent exenteration 73 weeks after radiother-
apy was completed.
For dogs that underwent surgery, perioperative
complications included epistaxis necessitating blood
transfusion (2 dogs) and self-limiting subcutaneous
emphysema (8). Surgical removal of the grossly visible
tumor was incomplete in 1 dog because of brain
involvement; this dog was euthanatized 8 days after
surgery because of complications.
In 9 of the 11 dogs, results of histologic examination
of biopsy specimens obtained at the time of nasal cavity
exenteration were positive for tumor cells. In the remain-
ing 2 dogs, only inflammatory changes were seen.
Complications—Nine of the 13 dogs in the radio-
therapy and surgery group developed rhinitis. Four of
these dogs had a single episode of rhinitis after under-
going nasal cavity exenteration; in all 4, the rhinitis
was responsive to treatment with amoxicillin or amox-
icillin-clavulanic acid. Five other dogs in this group
developed chronic or recurrent rhinitis that progressed
to osteomyelitis with or without bone necrosis and
persisted for 4 to 29 months. These dogs were treated
with a variety of antimicrobials, including amoxicillin-
clavulanic acid, enrofloxacin, cephalexin, doxycycline,
and metronidazole. One of these 5 dogs developed
rhinitis associated with an antimicrobial-resistant
Staphylococcus sp and required surgical debridement.
That dog developed a permanent nasocutaneous fistu-
la, and chronic mild rhinitis persisted until it died of
unrelated causes 29 months after radiotherapy was
completed. Two dogs developed persistent nasal
aspergillosis that was partially controlled for 30
months with intermittent administration of itracona-
zole; tumor recurrence was documented in both dogs.
Two dogs in the radiotherapy and surgery group
that had had extensive tumor-related bone destruction
prior to undergoing radiotherapy developed shortening
of the maxilla, resulting in a brachycephalic appear-
ance. One of those dogs developed an osteosarcoma of
the maxilla 5 years after undergoing radiotherapy.
Dogs in the radiotherapy-only group were not
administered antimicrobials following radiotherapy.
Four dogs in that group developed chronic rhinitis after
treatment. In 3 of the 4, rhinitis was associated with
osteonecrosis. Two of those dogs developed oronasal
fistulas at 5 and 9 months after radiotherapy. The one
that had the fistula at 5 months underwent 3 attempts
at surgical repair, but a small fistula persisted at the time
of euthanasia 31 months after radiotherapy. No tumor
recurrence was suspected. The other dog with an
oronasal fistula had 2 surgeries for bone debridement
and dental extraction and had a persistent fistula at the
time tumor recurrence was documented 21 months
after radiotherapy. That dog was euthanatized 4 months
later. The third dog developed a nasocutaneous fistula
near the medial canthus of 1 eye at 23 months after
radiotherapy. Despite 3 months of treatment with
trimethoprim-sulfonamide for a susceptible hemolytic
Streptococcus sp, the fistula was still draining 5 months
later when the dog died. The referring veterinarian
thought that extensive maxillary osteonecrosis con-
tributed to that dog’s death. No tumor recurrence was
suspected on the basis of computed tomographic find-
ings. The dog that developed chronic rhinitis was given
multiple courses of ampicillin between 1 and 9 months
after radiotherapy. Improvement was noted during peri-
ods of antimicrobial treatment, but signs recurred when
medication was discontinued. Rhinitis and recurrent
tumor with pulmonary metastasis were identified at
necropsy 9 months after radiotherapy was completed.
Three dogs in the radiotherapy and surgery group
eventually lost sight in the eye included in the radia-
tion field. Of these, 1 required enucleation 22 months
after radiotherapy was completed because of glaucoma.
Twelve dogs in the radiotherapy-only group lost sight
in 1 (8 dogs) or both (4) eyes following radiotherapy.
Of these, 3 underwent enucleation because of
descemetoceles or keratoconjunctivitis sicca.
Dogs in the radiotherapy and surgery group were
significantly more likely to develop rhinitis (relative
risk, 3.17; 95% confidence interval, 1.40 to 7.17) or
osteomyelitis-osteonecrosis (relative risk, 5.13; 95%
confidence interval, 1.40 to 18.6) than were dogs in the
radiotherapy-only group. The risk of blindness was not
significantly higher for dogs in the radiotherapy-only
group (relative risk, 1.30; 95% confidence interval,
0.43 to 3.91) than for dogs in the radiotherapy and
surgery group.
Two dogs in the radiotherapy and surgery group
and 1 in the radiotherapy-only group developed dental
caries and evidence of death of the pulp of teeth in the
radiation field that necessitated fillings, extractions,
Table 1⎯Signalment, clinical stage, and histologic type for dogs
with intranasal neoplasia enrolled in a study comparing outcome
of radiotherapy alone with outcome of radiotherapy followed by
exenteration of the nasal cavity.
Radiotherapy
alone
(n = 40)
Radiotherapy
and surgery
(13)Variable P value
Body weight (kg)
Sex
Male
Female
Age (y)
Clinical stage
1
2 13 (33)
3
4 14 (35)
Histologic type
Carcinoma
Adenocarcinoma
Anaplastic carcinoma
Squamous cell
carcinoma
Chondrosarcoma
Osteosarcoma
Soft tissue sarcoma
26.2 (6.0–42.6)25.6 (5.3–38.0)0.840
0.999
18 (45)
22 (55)
11.3 (2.7–14.7)
6 (46)
7 (54)
7.6 (5.9–12.0)0.024
8 (20) 2 (15)
3 (23)
4 (31)
4 (31)
0.999
0.740
0.200
0.999
0.690
5 (12)
9 (23)
12 (30)
12 (30)
0 (0)
3 (23)
3 (23)
2 (15)
2 (15)
4 (10)
0 (0)
3 (7)
1 (8)
1 (8)
1 (8)
Data are given as median (range) or number (percentage).

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JAVMA, Vol 227 , No. 6, September 15, 2005Scientific Reports: Retrospective Study939
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and root canal procedures 2.5 to 4 years after radio-
therapy. Numbers of dogs in each group that developed
these complications were too small to allow for statis-
tical analysis.
Outcome—Analysis of censored survival curves
indicated that 68%, 44%, 24%, and 12% of dogs in the
radiotherapy-only group were alive 1, 2, 3, and 4 years,
respectively, after completion of radiotherapy, com-
pared with 77%, 69%, 58%, and 46%, respectively, of
dogs in the radiotherapy and surgery group. Median
survival time for dogs in the radiotherapy-only group
(19.7 months) was significantly (P = 0.022) shorter
than median survival time for dogs in the radiotherapy
and surgery group (47.7 months; Figure 1), even after
controlling for age.
Twenty-six of the 40 (65%) dogs in the radiothera-
py-only group had local recurrence of intranasal neopla-
sia without evidence of metastasis. Nine of the 26 (35%)
dogs that underwent radiotherapy alone and had evi-
dence of recurrence of intranasal neoplasia without evi-
dence of metastases were euthanatized within 10 months
after completion of radiotherapy because of progressive
disease. Between 10 and 19 months following radiother-
apy, 7 more succumbed to progressive local disease;
between 20 and 29 months, another 3 succumbed to
local disease; and between 30 and 51 months, 4 more
succumbed to local disease. Two others were euthana-
tized because of metastasis < 9 months after radiothera-
py was completed, and 1 was euthanatized because of
metastasis 31 months after radiotherapy was completed.
Of the remaining 11 dogs, 9 died or were euthanatized
for unrelated disease 1 to 65 months after radiotherapy
and 2 remained alive without evidence of recurrence 34
and 47 months after radiotherapy.
Six of the 13 dogs in the radiotherapy and surgery
group had local recurrence of intranasal neoplasia 3 to
48 months after treatment, including both dogs that did
not undergo surgery. Of the remaining 7 dogs, 4 died or
were euthanatized for an unrelated cause 29 to 68
months after radiotherapy and 3 were alive without evi-
dence of recurrence 30 to 57 months after radiotherapy.
The rate of local recurrence of intranasal neoplasia
for dogs in the radiotherapy-only group (68%) was not
significantly different from the rate for dogs in the
radiotherapy and surgery group (60%) that have died.
Metastasis to the regional lymph nodes or lungs was
documented in 4 of the 40 (10%) dogs in the radio-
therapy-only group following radiotherapy; metastasis
was not observed in any of the dogs in the radiothera-
py and surgery group.
For the 40 dogs in the radiotherapy-only group,
median overall survival time for dogs with a carcinoma
(21.6 months) was not significantly (P = 0.603) differ-
ent from median overall survival time for dogs with a
sarcoma (18.3 months). No significant (P = 0.669) dif-
ferences in median overall survival times were detect-
ed among groups when the 40 dogs were grouped on
the basis of clinical stage prior to radiotherapy (stage 1,
25 months; stage 2, 21.6 months; stage 3, 11.6 months;
and stage 4, 18.3 months). Similarly, median survival
time for dogs classified as stage 1 or 2 prior to radio-
therapy was not significantly (P = 0.18) different from
median survival time for dogs classified as stage 3 or 4.
Discussion
In dogs with intranasal neoplasia, the condition is
generally advanced by the time of referral to a special-
ty center or teaching hospital and is not eliminated by
curative-intent radiotherapy in 60% to 80% of
dogs.3,4,7,16This coincides with findings in the present
study, in that tumor was identified histologically in 9 of
11 dogs that underwent surgery between 6 and 73
weeks after completion of radiotherapy.
Reported median survival times for dogs with
intranasal neoplasia treated with megavoltage radiother-
apy alone ranged from 8 to 14 months.3,4,16,17In the pre-
sent study, median survival time for the 40 dogs that
underwent radiotherapy without surgery, chemotherapy,
or immunotherapy was 19.7 months. However, 68% of
the dogs that underwent radiotherapy alone were eutha-
natized because of recurrence of clinical signs indicative
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
group and 1 dog in the radiotherapy and surgery group
that were euthanatized between 46 and 51 months after
radiotherapy because of local recurrence.
Figure 1—Kaplan-Meier graph of outcome of dogs with intranasal
neoplasia enrolled in a study comparing outcome of radiotherapy
(RT) alone with outcome of RT followed by exenteration of the
nasal cavity.

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In the present study, dogs that underwent nasal
cavity exenteration following radiotherapy had a sub-
stantial risk of developing postoperative complica-
tions. In particular, the risks of developing chronic or
recurrent rhinitis and osteomyelitis were significantly
higher for dogs in this group than for dogs that under-
went radiotherapy alone. Although these complica-
tions did not appear to affect outcome, chronic bacter-
ial or fungal rhinitis resulted in long-term management
responsibilities for the owners. During exenteration,
all nasal cavity tissue, including the periosteum lining
the nasal cavity, is removed. Healing occurs by forma-
tion of granulation tissue over the bone and subse-
quent epithelialization. A chronic nasal discharge is
common in dogs that undergo nasal cavity exentera-
tion (without radiotherapy) but commonly resolves
within a few months after surgery, although a serous or
purulent discharge may persist.18In dogs that undergo
radiotherapy prior to nasal cavity exenteration, howev-
er, the compromised blood supply in the underlying
bone could impair healing of the exposed bone sur-
faces, resulting in poorly vascularized granulation tis-
sue that is susceptible to opportunistic infection. One
approach that might help to reduce this problem would
be to resect turbinates only in the area of any persistent
or recurrent tumor. However, this presents a challenge
because it can be difficult to identify the margins of a
nasal tumor in the presence of substantial exudate and
grossly abnormal, but nonneoplastic, turbinate tissue.
In such a situation, it may be advisable to preserve the
periosteal lining of the nasal cavity as much as possible
to minimize compromise of the blood supply to the
bone surfaces. This approach may better preserve local
defenses against opportunistic infection and reduce the
incidence of postsurgical rhinitis and osteomyelitis. We
currently recommend long-term (months) treatment
with broad-spectrum antimicrobials (typically amoxi-
cillin-clavulanic acid) to reduce the incidence and
severity of bacterial rhinitis in dogs undergoing nasal
cavity exenteration following radiotherapy.
An unexpected late effect observed in the present
study was the development of caries and dental pulp
death between 2.5 and 4 years after radiotherapy. Tooth
death and xerostomia-induced caries are well-recog-
nized late complications following radiotherapy of oral
and maxillary neoplasms in human patients.19-22The
paucity of information regarding this complication in
dogs may be attributable to limited information con-
cerning long-term outcome of dogs that have under-
gone radiotherapy of tumors of the head.
Results of previous studies3,17suggest that doses com-
monly used for megavoltage radiotherapy of intranasal
neoplasia in dogs are inadequate. However, increasing the
radiation dose or using a radiation sensitizer can lead to
severe acute mucositis, ocular inflammation, or skin
necrosis and therefore may not be advisable.11,23Use of
surgery following completion of radiotherapy, as
described in the present report, appears to offer a viable
alternative.
The relationship, if any, between histologic type
and outcome for dogs with intranasal neoplasia is con-
troversial1,2,4; however, recent reports3,7,10have not sub-
stantiated any such relationship. In the present study,
we also did not find any difference in survival time
between groups when dogs were grouped on the basis
of histologic type.
Age of the dog at the time of radiotherapy has pre-
viously been suggested to be associated with outcome
in dogs with intranasal neoplasia.3Although median
age of dogs in the radiotherapy and surgery group in
the present study was significantly less than median
age of dogs in the radiotherapy-only group, we did not
identify any effect of age on overall survival time in the
present study.
Whether there is any relationship between clinical
stage and outcome in dogs with intranasal neoplasia is
also controversial.3,4,7In a previous studyathat used the
same radiotherapy protocol used in the present study,
clinical stage was significantly associated with survival
time. In the present study, however, no significant dif-
ference in survival time was found among groups when
dogs that underwent radiotherapy alone were grouped
on the basis of pretreatment clinical stage.
For dogs in the present study, the time between
radiotherapy and nasal cavity exenteration was deter-
mined for individual dogs on the basis of results of fol-
low-up computed tomography. However, the specifici-
ty of computed tomography for identifying viable
tumor following radiotherapy must be in question.
Two dogs in the present study that had a 50% to 70%
reduction in tumor volume on computed tomograms
obtained 6 weeks after radiotherapy had no histologic
evidence of tumor at the time of surgery and died of
unrelated causes 28.5 and 52 months after undergoing
radiotherapy. Conversely, a dog that had an 80% to
90% reduction in tumor volume on a computed tomo-
gram obtained 11 weeks after radiotherapy had histo-
logic evidence of viable tumor cells at the time of
surgery. The most accurate means of documenting per-
sistent viable tumor is probably comparison of serial
computed tomograms or magnetic resonance images
for evidence of progressive disease. The use of positron
emission tomography would theoretically also be a
means of determining viability of suspected persistent
tumor; however, documentation of progressive disease
on serial imaging studies is still the most accurate
means of identifying residual tumor.
Limitations of the present study include the small
number of dogs in the radiotherapy and surgery group
and the lack of consistent follow-up computed tomogra-
phy for dogs in the radiotherapy-only group, which pre-
cluded an accurate determination of the time to local
recurrence. The finding in the present study that survival
time was longer in dogs that underwent surgery will
require verification with a randomized controlled trial in
which groups undergo identical follow-up. Despite these
limitations, the longer survival time for dogs in the radio-
therapy and surgery group in the present study suggests
that further application and evaluation of this treatment
strategy for intranasal neoplasia are warranted.
a.Green EM, Adams WM, Forrest LJ, et al. Accelerated RT for canine
nasal neoplasia (abstr). Vet Radiol Ultrasound 2003;44:113.
Prowess 3000 Radiotherapy Treatment Planning System, SGGI,
Chico, Calif.
Prism 4, GraphPad Software, San Diego, Calif.
b.
c.

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