Outcomes of Cats With Oral Tumors Treated With Mandibulectomy: 42 Cases
Medical records of 42 cats treated with mandibulectomy for oral neoplasia at eight institutions were reviewed to determine morbidity, progression-free interval, and survival time. Progression-free and survival rates at 1 and 2 years were 56% and 49%, and 60% and 57%, respectively. Cats with squamous cell carcinoma had significantly shorter survival than cats with fibrosarcoma or osteosarcoma. Seventy-two percent of cats were dysphagic or inappetent immediately postoperatively, and 12% never regained the ability to eat. Despite acute morbidity in 98% and long-term morbidity in 76% of cats, 83% of the 30 owners providing information were satisfied with the outcome of mandibulectomy.
Introduction
Functional outcome and tumor control are major concerns when considering mandibulectomy as a therapeutic option for tumors of the oral cavity. Squamous cell carcinoma and fibrosarcoma are the most common oral tumors of the cat.1,2 These tumors are locally aggressive, and recurrence after surgical resection is common. Descriptions of only 21 cats treated with mandibulectomy have been reported.3–8 Sixteen of these cats were clinically abnormal after mandibulectomy, exhibiting signs such as protrusion of the tongue, ptyalism, dysphagia, and medial migration of the remaining mandible (i.e., mandibular drift).3–8 Three cats died because of postoperative dysphagia. Two were unable to prehend food, and one aspirated food.3–5 The outcomes for these cats suggested that mandibulectomy may have a significant negative impact on the oral function and quality of life of treated cats.
The majority (15 of 21) of cats described in previous reports of mandibulectomy were treated for squamous cell carcinoma.3–5,7 Eleven of these cats experienced recurrences, including six of seven cats treated with mandibulectomy followed by definitive radiation therapy.7 For the eight cats treated with mandibulectomy alone for squamous cell carcinoma, five experienced recurrences, and the median survival time was 5.5 months (range 5 weeks to 12 months).3–5 Only two of these eight cats survived 10 months, suggesting that even aggressive surgery might be inadequate for local control of oral squamous cell carcinoma in the cat.3–5
Based on the limited information available on cats treated with mandibulectomy, the locally invasive nature of most feline oral neoplasms, and the small size of the feline mandible, the hypothesis of the study reported here was twofold: mandibulectomy would be ineffective for local control of oral tumors in cats, and a mandibulectomy aggressive enough to successfully control oral tumors in cats would result in permanent loss of oral function and compromised quality of life. The purpose of this retrospective study was to evaluate postoperative survival time, tumor control, and morbidity in a large number of cats treated with mandibulectomy.
Materials and Methods
Case Material
The medical records of all cats treated with mandibulectomy at eight participating veterinary referral hospitals between October 1984 and January 2002 were retrospectively reviewed. Each cat included in this study had a mandibulectomy for oral neoplasia and had follow-up information available on tumor control and survival time.
Information collected from the medical records describing treated cats included age, gender, presenting clinical signs, duration of clinical signs prior to presentation, and histopathological diagnosis. Information collected regarding the oral tumor included location, size, presence of osteolysis on mandibular imaging with radiography or computed tomography (CT), completeness of excision based on histopathological evaluation of the margins of excised tissues, results of thoracic radiography, and results of mandibular lymph node cytological examination. Staging tests, including imaging of the mandible, lymph node cytology, and thoracic radiography, were performed at the discretion of the attending clinician. When the information was available in the medical record, clinical tumor stage (based on the diameter of the primary tumor) was classified as T1 (<2 cm), T2 (2 to 4 cm), or T3 (>4 cm) according to the World Health Organization (WHO) Tumor, Node, Metastasis (TNM) system.9 To further define tumor stage, if imaging of the mandible was performed, the presence of osteolysis was included in the WHO stage description (i.e., substage a [no osteolysis] versus substage b [osteolysis present]).
Information obtained regarding treatment included type of surgery performed, whether an enteral feeding tube was placed, duration of the feeding tube, postoperative oral function and complications (e.g., ability to eat, ptyalism, tongue protrusion, malocclusion, palate trauma, mandibular drift), and any additional therapy. The types of surgery performed were described as complete unilateral mandibulectomy, bilateral rostral mandibulectomy, resection of >50% of the mandible (i.e., complete unilateral mandibulectomy combined with partial resection of the contralateral mandible or bilateral rostral mandibulectomy with removal of >50% of the mandible), or segmental unilateral mandibulectomy.2 The type of mandibulectomy performed was based on the surgeon’s judgment of the appropriate procedure for the cat and the tumor. Acute morbidity was defined as complications of surgery noted during the first 4 weeks after surgery, and long-term morbidity was defined as complications that did not resolve during the cat’s lifetime or follow-up time.
Outcome information retrieved from the medical records included development of local recurrence as determined by physical examination, development of metastasis, progression-free interval (i.e., the time, in days, from mandibulectomy until detection of local tumor recurrence or metastasis), survival status, survival time (i.e., the time, in days, from mandibulectomy until death from any cause), cause of death, and owner satisfaction with outcome. Additional follow-up information was obtained by telephone communication with owners and referring veterinarians. Owner satisfaction with outcome was assessed from written reports in the medical records or from direct communication with the owners. Parameters evaluated to determine postmandibulectomy quality of life and owner satisfaction included the cat’s ability to prehend food, the cat’s quality of life as perceived by the owner, whether the owners were satisfied with the outcome of the surgery, and whether they would consider mandibulectomy surgery again.
Statistical Analysis
Median survival time and progression-free interval were estimated using the Kaplan-Meier method.10 Cats that were alive or disease-free at the time of last follow-up were included until the day of last follow-up and then censored from the respective analysis. Cats that died of causes unrelated to their oral tumors were censored from the analysis of survival time on the day of their death. Survival curves were generated using GraphPad Prism software.a Statistical testing was performed using SAS software.b Logrank tests were used to evaluate the relationship of variables to survival time and progression-free interval if there were sufficient numbers of cats in the variable groups to allow analysis.11 The relationship of progression-free interval and survival time to the following variables was evaluated: diagnosis (i.e., squamous cell carcinoma versus fibrosarcoma or osteosarcoma), WHO tumor stage, tumor location (i.e., rostral versus other), type of surgery (i.e., bilateral rostral versus complete unilateral mandibulectomy), histopathological evidence of completeness of excision, and use of additional therapies. For all analyses, significance was defined as P≤0.05.
Results
The inclusion criteria for this study were met by 42 cats undergoing mandibulectomy from October 1984 to January 2002 at Colorado State University (n=21), Tufts University (n=6), University of Georgia (n=4), Cornell University (n=3), Veterinary Centers of America (VCA) West Los Angeles Animal Hospital (n=3), University of California-Davis (n=2), All-Care Animal Referral Center (n=2), and South Bay Veterinary Specialists (n=1).
The median age of the cats was 11.2 years (range 1 to 18 years). Twenty-three cats were castrated males, 18 were spayed females, and one was an intact male. Presenting clinical signs included a visible mandibular mass (n=39; one noted by the referring veterinarian at a routine dentistry), ptyalism (n=10; four with hemorrhage from the tumor), dysphagia (n=7), inappetence and/or anorexia (n=5), weight loss noted by the owner (n=3), halitosis (n=3), behavioral changes (n=3), inability to open the mouth (n=1), pain perceived by owner (n=1), pawing the mouth (n=1), and cessation of grooming (n=1). The median duration of clinical signs prior to presentation was 28 days (range 1 day to 6 years).
Histopathological diagnoses included squamous cell carcinoma (n=21), fibrosarcoma (n=6), osteosarcoma (n=6; one parosteal), salivary gland adenocarcinoma (n=2), lymphoma (n=2; one with concurrent radiation-induced osteonecrosis of the mandible), undifferentiated carcinoma (n=1), chondrosarcoma (n=1), acanthomatous epulis (n=1), melanoma (n=1), and osteoma (n=1). Clinical data and outcomes of cats with the three most common tumor types are summarized in Table 1. Tumor location on the mandible was rostral (n=19), entire unilateral mandible (n=7), caudal unilateral mandible (n=4), middle unilateral mandible (n=3), and not recorded in nine cats (all treated with complete unilateral mandibulectomy). Primary tumors were clinically staged as T1 (n=8), T2 (n=11), or T3 (n=13) based on visual measurement. Ten did not have tumor measurements documented in the medical record. Results of radiographic or CT examinations were available for 30 cats, and osteolysis was evident in 27 of the mandibles. Cats with available tumor measurements and radiographic assessment of osteolysis were able to be staged as T1a (n=1), T1b (n=4), T2b (n=8), or T3b (n=11). Cytological examination of fine-needle aspirates of the ipsilateral mandibular lymph node (n=11) revealed no evidence of metastasis. Thoracic radiographs revealed no evidence of metastasis (n=39). The only cat with abnormal radiographic findings was diagnosed with mandibular osteosarcoma and had a 1-cm pulmonary nodule identified at the time of mandibulectomy. No further radiographs were obtained, and this cat was euthanized 238 days following mandibulectomy for recurrent local disease. No necropsy was performed.
Surgical procedures performed included complete unilateral mandibulectomy (n=21), bilateral rostral mandibulectomy (n=12), resection of >50% of the mandible (n=6), and segmental unilateral mandibulectomy (n=3). No intraoperative complications were noted. One cat developed cardiopulmonary arrest of unknown cause and died 3 to 4 hours after a complete unilateral mandibulectomy for squamous cell carcinoma.
Histopathological descriptions of the surgical margins were available for 33 tumors. Seventeen specimens (seven of squamous cell carcinoma, three of osteosarcoma, two of fibrosarcoma, and one each of chondrosarcoma, undifferentiated carcinoma, osteoma, acanthomatous epulis, or amelanotic melanoma) had no microscopic evidence of tumor at the margins. Sixteen specimens (nine squamous cell carcinomas, two fibrosarcomas, two osteosarcomas, two salivary adenocarcinomas, and one lymphoma) had microscopic residual disease. Surgical margins were clean for six of 12 cats that underwent bilateral rostral mandibulectomy, nine of 21 cats that underwent complete unilateral mandibulectomy, and two of six cats that underwent resection of >50% of the mandible. Microscopic residual disease was found in three of 12 cats treated with bilateral rostral mandibulectomy, seven of 21 cats treated with complete unilateral mandibulectomy, three of six cats treated with resection of >50% of the mandible, and all three cats treated with segmental unilateral mandibulectomy.
One cat died within hours of mandibulectomy, and another cat had no available information on postoperative morbidity in the medical record. Acute morbidity was observed in 39 (98%) of the remaining 40 cats. Most cats experienced more than one adverse effect in the 4 weeks following surgery [Table 2]. Because it was difficult to distinguish between dysphagia and inappetence based on the information provided in medical records, cats were described as having abnormalities in eating.
At the end of the study, 27 cats were dead, 12 cats were alive, and three cats were lost to follow-up at 237, 357, and 963 days. The median follow-up time for the 15 surviving cats was 813 days (range 186 to 2137 days). The date of latest follow-up was August 4, 2002. The median survival time for all 42 cats was not reached (range 0 to 2920 days), and 1- and 2-year survival rates were 60% and 57%, respectively [Figure 1]. In the logrank analysis, tumor type was the only variable significantly associated with survival time [Table 3]. A diagnosis of squamous cell carcinoma was associated with shorter survival time (P=0.03) compared to fibrosarcoma and osteosarcoma [Figure 2].
Fourteen cats (including eight with squamous cell carcinomas, two with fibrosarcomas, and one each with an osteosarcoma, chondrosarcoma, salivary gland adenocarcinoma, or lymphoma) were euthanized because of progression of local disease. One cat with squamous cell carcinoma was euthanized for lymph node metastasis with no evidence of local recurrence at 217 days following complete unilateral mandibulectomy. Another cat was euthanized for dyspnea from mandibular lymph node and pulmonary metastasis of salivary gland adenocarcinoma at 444 days after segmental unilateral mandibulectomy. It was not possible to determine from the medical record of this cat whether the dyspnea was associated with upper airway obstruction or pulmonary/pleural involvement. Multiple pulmonary nodules were detected 7 months prior to euthanasia, and local recurrence was also present at the time of euthanasia. These two cats were the only ones for which initial tumor progression and death could be attributed to metastatic disease. Three additional cats with squamous cell carcinomas developed lymph node metastasis at the time of or after local tumor recurrence, but they were euthanized because of local progression of the oral masses.
Eighteen cats developed local tumor recurrence during the follow-up time of the study. These 18 cats included eight with squamous cell carcinoma, four with fibrosarcoma, one with osteosarcoma, two with salivary gland adenocarcinoma, two with lymphoma, and one cat with chondrosarcoma. The median progression-free interval for all 42 cats was 544 days, and 1- and 2-year progression-free rates were 56% and 49%, respectively [Figure 3]. Stages of the tumors that recurred included T1 (n=2), T2 (n=5), and T3 (n=4). Local recurrence was noted in 10 tumors removed by complete unilateral mandibulectomy, four removed by bilateral rostral mandibulectomy, one removed by resection of >50% of the mandible, and all three tumors removed by segmental unilateral mandibulectomy. Local recurrence was noted for nine tumors with histopathological evidence of residual disease at the surgical margins and for four tumors with no microscopic residual disease. Three of the four tumors that recurred despite apparent complete resection were squamous cell carcinomas, and the fourth was chondrosarcoma. Six of the seven tumors that did not recur despite apparent incomplete resection were squamous cell carcinomas. The cats with incompletely excised squamous cell carcinoma that did not develop recurrence by the end of the study had a median follow-up time of 169 days (range 11 to 813 days), and two of them received adjunctive radiation therapy and chemotherapy. The seventh cat with no recurrence, despite apparent incomplete resection, had an osteosarcoma and was treated with adjunctive radiation therapy. This cat was still alive 1688 days after surgery. In logrank analysis, none of the variables examined correlated significantly with the progression-free interval [Table 4; Figure 4].
Information regarding acute and long-term complications of mandibulectomy was available for 40 and 38 cats, respectively. This information is summarized in Table 2. One cat developed dehiscence after the second week of definitive radiation therapy following complete unilateral mandibulectomy for osteosarcoma. For this cat, tumor excision was incomplete based on histopathological evaluation of margins, and radiation therapy was initiated at approximately 30 days after surgery. Another cat developed a ranula 3 months after complete unilateral mandibulectomy for squamous cell carcinoma. Only nine cats were described as completely normal after recovery.
Five cats had severe anorexia and/or dysphagia that prevented them from eating to the time of their death. One of these cats died of dilated cardiomyopathy 11 days after complete unilateral mandibulectomy. Three cats were euthanized at 9, 37, and 68 days postmandibulectomy because of inability to eat. The cat that was euthanized 9 days after bilateral rostral mandibulectomy did not have a feeding tube placed for nutritional support. The cats that survived 37 and 68 days had >50% of the mandible removed, and enteral feeding tubes were placed at the time of mandibulectomy. Another cat treated with resection of >50% of the mandible was euthanized 192 days after surgery for local recurrence; this cat never regained the ability to eat and was maintained with a feeding tube. Notably, three of the six cats with >50% of the mandible removed never regained the ability to eat. Enteral feeding tubes were placed in 17 of the 42 cats. Tubes were placed in five cats that had resection of >50% of the mandible, in 10 cats that had a complete unilateral mandibulectomy, in one cat that underwent a segmental unilateral mandibulectomy, and in one cat that had a bilateral rostral mandibulectomy. Feeding tubes were in place for a median of 74 days (range 2 to 192 days).
Of 30 owners providing information, 25 (83%) were pleased with the outcome of mandibulectomy, and five (17%) regretted the surgery, citing reasons such as inability of the cat to prehend food and water (n=4), inability to groom (n=2), ptyalism (n=1), rapid tumor recurrence (n=1), and poor quality of life during the postoperative recovery period (n=1).
Three cats (one each with squamous cell carcinoma, fibrosarcoma, or lymphoma) were treated with mandibulectomy following local recurrence of their tumor after radiation therapy and chemotherapy (the cats with fibrosarcoma and lymphoma only). The survival times for these three cats were 128 (squamous cell carcinoma), 720 (alive at last follow-up, fibrosarcoma), and 147 (lymphoma) days.
Twelve cats received additional treatments for their oral tumors after undergoing mandibulectomy. These adjunctive treatments included chemotherapy (n=5), radiation therapy (n=2), radiation therapy and chemotherapy (n=3), and piroxicamc (n=2). The median progression-free interval and median survival time for cats receiving adjunctive therapy were 280 and 217 days, respectively, compared to 850 days and not reached at 2920 days for cats that received surgery alone. There was no significant difference in progression-free interval or survival time of cats that received additional therapies compared to those treated with mandibulectomy alone (P=0.53 and P=0.44, respectively). Because of the inconsistencies in adjunctive therapies used, no conclusions could be made regarding the effects of these therapies.
Discussion
The most common reason for performing mandibulectomy in cats is resection of oral neoplasia. Outcomes and owner satisfaction with mandibulectomy for control of canine oral tumors have been well documented.12–16 A literature search revealed much less information describing the outcome of this surgery in cats.3–8 Because most feline oral tumors are locally invasive and the amount of tissue that may be resected is small, it was expected that mandibulectomy would not achieve local control of most tumors and that performing a more aggressive mandibulectomy procedure (to improve local control of tumors) would result in permanent loss of oral function and compromised quality of life. Contrary to the hypothesized outcome, tumor control for most of the cats in this study was surprisingly good, with a median progression-free interval of almost 1.5 years. Survival rates at 1 year postmandibulectomy were the same as those at 2 years postmandibulectomy for cats with squamous cell carcinoma, fibrosarcoma, or osteosarcoma—suggesting that if a cat lived 1 year, the chance of long-term survival was good.
In particular, cats with fibrosarcoma or osteosarcoma enjoyed long progression-free and survival times, and the majority of these cats did not die of tumor-related causes. Despite the small numbers of cats with fibrosarcoma or osteosarcoma in this study, the information regarding their outcome was useful since no studies have been published that specifically describe the treatment for cats with these tumors. Considering the fact that four of six cats with fibrosarcoma had recurrences, compared to only one of six cats with osteosarcoma, fibrosarcoma may be more difficult to control locally than osteosarcoma. A study including more cats with longer follow-up times would be necessary to determine whether this hypothesis is true.
Although cats with squamous cell carcinoma had significantly shorter survival times than those with fibrosarcoma or osteosarcoma, superior tumor control and survival times were detected in this study when compared to those reported previously for cats with squamous cell carcinoma treated with mandibulectomy.3–5 These results may have been a consequence of bias in case selection or perhaps improved patient management, better methods of imaging tumors, surgical techniques, and postoperative care. Although the study reported here did not find improved survival times for cats that received adjunctive therapy, the use of additional therapies in some cats with squamous cell carcinomas may have improved their tumor control and survival. The longest survival time reported to date for cats with oral squamous cell carcinoma was in a study of seven cats treated with mandibulectomy and adjunctive definitive radiation therapy, resulting in a median survival time of 14 months.7 This small study suggests that curative-intent radiation therapy might extend the survival times of cats undergoing mandibulectomy for squamous cell carcinoma.7 Because adjunctive treatments varied in nature and were applied inconsistently in the study reported here, conclusions regarding their efficacy were not possible.
Unfortunately, because of the small numbers of cats in each variable category, this study was not able to identify prognostic indicators for cats with oral squamous cell carcinoma. The significant association of squamous cell carcinoma with survival time but not progression-free interval was likely the result of the small number of cases and the large amount of censored data in this study, because not all cats died of their oral tumors.
Forty-six percent of the treated cats that survived >2 weeks following surgery developed local recurrences, and it is possible that the recurrence rate might have been higher if longer follow-up data were available. This high recurrence rate suggested that the extent of disease was underestimated at the time of surgery and that it was often impossible to obtain adequate margins of normal tissue with mandibulectomy. Consequently, careful case selection and surgical planning that includes advanced imaging may be essential to achieve complete excision of the tumor.
Concern regarding the potential for surgical complications that result in impaired oral function and negatively impact the quality of life of affected cats was a major impetus for the initiation of this study. During the 4 weeks following surgery, almost all cats experienced adverse effects. The description of adverse effects in this study likely underestimated the number of cats experiencing side effects, because it was limited to information in the medical records and the recollections of owners and referring veterinarians. Because owners were asked to describe outcomes retrospectively, their recollections may have been biased and may have resulted in decreased reporting of morbidity. In addition, evaluation of surgical morbidity may have been confounded by the use of additional therapies in some cats.
Despite these limitations, this study demonstrated considerable acute postoperative morbidity. The nature of the adverse effects observed suggested that hospitalization, analgesics, intravenous fluids, and enteral feeding with a feeding tube may improve the quality of life for cats immediately following mandibulectomy. These adverse effects should be discussed thoroughly with cat owners prior to mandibulectomy. For example, cats that develop mandibular drift and resulting malocclusion may require contralateral mandibular canine tooth extraction or vital pulpotomy to prevent damage of the hard palate. Cats that develop ptyalism or tongue protrusion following surgery often require increased efforts by the owners to keep the area clean and to provide some generalized grooming for the cat.
It was surprising that although 76% of the cats of this study experienced adverse effects for the remainder of their lives, 25 (83%) owners were pleased with their cat’s quality of life and would choose the procedure again under the same circumstances. This level of acceptance suggested that the long-term complications did not greatly impact the quality of life for the cats. There were, however, cats that experienced life-threatening morbidity. Five cats never regained the ability to prehend food, and three of these cats had resection of >50% of the mandible. Although the number of cats undergoing resection of >50% of the mandible was too small to allow detection of a difference in survival time, the fact that half of these cats never regained the ability to pre-hend food suggested that the surgery was too aggressive to allow a functional outcome.
Conclusions based on this study were limited by its retrospective and multi-institutional nature. The ability to detect differences in progression-free interval or survival time as they related to selected variables was limited by the small number of cats in each group and the large number of censored individuals. A larger, prospective study with uniform treatments and follow-up times might be better able to define prognostic indicators for cats undergoing mandibulectomy for oral tumors. Possible positive prognostic indicators meriting further investigation based on the results of the current study include a rostral location and complete excision of the tumor. Finally, both the description of adverse effects and the analysis of survival were potentially confounded by the limited and inconsistent application of various adjunctive therapies. To increase the number of cats described, this study included 12 cats treated with additional therapies. It was possible that the additional therapies influenced survival and/or complication rates. Cats receiving additional treatments had lower progression-free and survival rates, possibly owing to a selection bias from additional therapies being recommended more commonly in cats suspected to have a poorer prognosis. Despite these limitations, there were no significant differences in the progression-free interval or survival time of cats receiving additional treatments versus cats treated with mandibulecto-my alone, and inclusion of these cats provided valuable additional information.
Conclusion
This retrospective study describes the outcomes for 42 cats treated with mandibulectomy for oral tumors. Results of the study suggest that mandibulectomy provides reasonable local control and an adequate quality of life for some cats with oral tumors. Although the majority of cats experienced complications from the surgery, most owners reported satisfaction with outcome. A diagnosis of oral squamous cell carcinoma was associated with a poorer prognosis compared to fibrosarcoma and osteosarcoma. Further prospective studies incorporating uniform treatments and prolonged follow-up times are required to better define prognostic indicators for cats undergoing mandibulectomy for oral neoplasia.
Prism 4; GraphPad Software, Inc., San Diego, CA 92130
SAS Version 8.2; SAS Institute, Inc., Cary, NC 27513-2414
Feldene; Pfizer, Inc., New York, NY 10017
Acknowledgment
The authors thank Antony S. Moore, MVSc, Diplomate ACVIM (Oncology) for his assistance with this manuscript.
Citation: Journal of the American Animal Hospital Association 42, 5; 10.5326/0420350
Citation: Journal of the American Animal Hospital Association 42, 5; 10.5326/0420350
Citation: Journal of the American Animal Hospital Association 42, 5; 10.5326/0420350
Citation: Journal of the American Animal Hospital Association 42, 5; 10.5326/0420350
Kaplan-Meier curve depicting survival time (in days) for 42 cats treated with mandibulectomy for oral neo-plasia. Small, vertical lines indicate days of last follow-up for living cats and cats dying of unrelated diseases. The median survival time was not reached at 2920 days.
Kaplan-Meier curves illustrating survival time (in days) for 33 cats treated with mandibulectomy for oral squamous cell carcinoma (SCC), fibrosarcoma (FSA), or osteosarcoma (OSA). Small, vertical lines indicate days of last follow-up for living cats and cats dying of unrelated diseases. The median survival time was significantly shorter (P=0.03) for cats with squamous cell carcinoma (217 days) compared to cats with fibrosarcoma or osteosarcoma (median survival times not reached).
Kaplan-Meier curve depicting the progression-free interval (in days) for 42 cats treated with mandibulectomy for oral neoplasia. Small, vertical lines indicate days of last follow-up for cats with no local recurrence or metastasis. The median progression-free interval was 544 days.
Kaplan-Meier curves illustrating the progression-free interval (in days) for 33 cats treated with mandibulectomy for oral squamous cell carcinoma (SCC), fibrosarcoma (FSA), or osteosarcoma (OSA). Small, vertical lines indicate days of last follow-up for cats with no local recurrence or metastasis. Differences in progression-free interval based on diagnosis of squamous cell carcinoma versus fibrosarcoma or osteosarcoma were not statistically significant (P=0.16).
