Canine and feline nasal tumors - Veterinary Medicine
  • SEARCH:
Medicine Center
DVM Veterinary Medicine Featuring Information from:

ADVERTISEMENT

Canine and feline nasal tumors
Detecting this mainly localized disease process early is difficult but important to improve an animal's prognosis. New advances in radiation technology may also help improve the outcome of dogs and cats with these neoplasms.


VETERINARY MEDICINE


While earlier studies evaluated the effects of surgery followed by radiation therapy, one recent study assessed the effects of radiation therapy followed by surgical exenteration of the nasal cavity. In this study, 53 dogs were treated with radiation therapy delivered in 10 fractions of 4.2 Gy, and in a small subset (n=13) of dogs, surgical exenteration of the nasal cavity was performed to remove any residual tumor burden. Interestingly, dogs adjuvantly treated with nasal cavity surgical exenteration had a median survival time of 47.7 months—much longer than dogs receiving only radiation therapy, which had a median survival time of 19.7 months.38 The one-, two-, and three-year survival rates for the radiation therapy-only group were 68%, 44%, and 24%, respectively. For the radiation therapy-and-surgical-exenteration group the survival rates were 77%, 69%, and 58%, respectively. Local tumor recurrence rates were not significantly different between treatment groups, but chronic complications including osteomyelitis and rhinitis were significantly higher in dogs treated with radiation therapy and surgical exenteration.

Radiation therapy combined with chemotherapy. Systemic chemotherapy has been classically indicated for the treatment of disseminated metastatic disease. However, the achievement of high local concentrations within the primary tumor microenvironment may allow for systemic chemotherapy to exert direct anticancer activities, which may contribute to the localized control of nasal tumors. Few studies have been conducted to determine the single-agent effectiveness of chemotherapy for the management of nasal tumors; however, some evidence would suggest that cisplatin in dogs exerts direct anticancer effects at the level of the primary nasal tumor.47

Despite some evidence for single-agent chemotherapy in the management of nasal tumors, a greater number of studies have focused on evaluating chemotherapeutics, such as cisplatin, as radiosensitizing agents rather than direct cytotoxic drugs. In a small preliminary study, 13 dogs with nasal tumors were treated with megavoltage radiation and a slow release polymer impregnated with cisplatin (implanted intramuscularly at a distant site) at a dosage of 60 mg/m2 to evaluate the feasibility and safety of this novel polymer system as a radiosensitizer. The release of cisplatin by the polymer system did not cause any systemic drug toxicosis; however, a low incidence (15%) of local tissue reaction at the site of polymer implantation was documented. More important, acute radiation side effects to normal tissue within the prescribed radiation field did not appear to be exacerbated by radiosensitization. Impressively, the median survival time achieved in this small preliminary study was 580 days, a clinically substantial improvement over historical radiation studies.48

In a larger follow-up study using the same combination protocol, 51 dogs were treated and also demonstrated unusually good survival times (median 15.8 months). Despite the positive survival times, most dogs (67%) still experienced disease relapse or progression.39 Similar to the original pilot study, it was confirmed that the cisplatin polymer was well-tolerated and did not seem to increase the incidence of early- or late-radiation toxicity effects.39

Finally, a third study compared the survival times between dogs with nasal tumors treated with radiation alone or radiation in conjunction with every-other-day, low-dose (7.5 mg/m2 ) intravenous cisplatin. Although low-dose cisplatin administered every other day resulted in some dogs developing azotemia, overall the protocol was well-tolerated but failed to improve survival times compared with dogs treated with radiation alone.49

Palliative radiation therapy. The goal of palliative radiation therapy is to reduce the tumor burden and improve quality of life. Most commonly, palliative radiation protocols deliver large fractions of radiation (6 to 8 Gy fractions) once or twice weekly for a total of four to six treatments. This palliative dosing strategy typically ameliorates clinical signs associated with disease but is insufficient to dramatically reduce tumor burden for prolonged time periods as compared with definitive treatment protocols.

In one study, 56 dogs with nasal tumors were treated weekly for four consecutive weeks with 9 Gy fractions. Most dogs (53/56) experienced improvements in clinical signs and minimal late radiation toxicity effects. The median survival time was 212 days, with reported one- and two-year survival rates of 45% and 15%, respectively.14

In a second retrospective study, the responses and survival times of 48 dogs were characterized after treatment with varying palliative radiation protocols. The cumulate radiation dosage administered ranged from 16 to 40 Gy, reflecting the diversity in treatment protocols instituted. Despite the lack of uniformity in treatment protocols, clinical signs in most dogs (66%) resolved completely after therapy for a median duration of 120 days, and the overall median survival time of dogs in this study was 146 days.40

Most recently, a study evaluating coarsely fractionated, palliative radiation therapy based on CT-based three-dimensional treatment planning in 38 dogs with nasal tumors has been reported. The therapeutic effects of three palliative protocols were studied: 1) 8 Gy fractions x four treatments, 2) 6 Gy fractions x five treatments, and 3) 3 Gy fractions x 10 treatments. All dogs treated were subjectively reported to have amelioration in their clinical signs after the completion of palliative therapy, and the median survival time reported for this group of 38 dogs was 10 months. Dogs with early stage disease (T1) intuitively had longer progression-free intervals (21.3 months) than dogs with more advanced disease (T2) did (8.5 months).50

Additional supportive measures

Dogs not receiving any form of definitive therapy (radiation, chemotherapy, surgery) tend to have relatively short median survival times ranging from 95 to 153 days.5,7,13 However, several options should be considered for improving the quality of life for dogs not receiving more conventional treatments. Based on their invasive phenotype, it is likely that dogs with nasal tumors experience discomfort and pain, so analgesics should be instituted to improve quality of life scores.

TREATMENT AND PROGNOSIS IN CATS

Compared with dogs, fewer studies document treatment options and outcomes for cats with nasal tumors. The most common tumor histopathologies that develop in the nasal passages of cats are lymphoma and carcinoma. Given the exquisite sensitivity of lymphoma to conventional radiation and chemotherapy, a definitive diagnosis in cats with obstructive nasal disease is necessary to provide owners with the most accurate prognostic and therapeutic recommendations.


Figure 7A. Atypical feline nasal lymphoma, presenting with disfiguring tumor proliferation involving the apical aspect of the nasal planum. (Image courtesy of Louis-Philippe de Lorimier, DVM, DACVIM [oncology].)
Several recent studies have described the outcome of cats with nasal lymphoma after treatment with radiation alone, chemotherapy alone, or a combination of radiation and chemotherapy. In one study, 19 cats with nasal lymphoma treated with fractioned megavoltage radiation (median dosage of 42 Gy) and six months of systemic multiagent chemotherapy achieved a median survival time of 945 days and a three-year survival rate of 26%.51 In a larger, multi-institutional retrospective study, 97 cats with nasal lymphoma were evaluated for survival time after treatment with radiation, chemotherapy, or both. Regardless of treatment options, the median survival time of cats in this study was 536 days. No significant differences in survival times among cats receiving radiation alone (n=19), chemotherapy alone (n=18), or the radiation and chemotherapy combination (n=60) were detected, suggesting that nasal lymphoma may be equally and effectively managed with any of the evaluated treatment combinations.52 Finally, a recent study evaluated the responsiveness of feline extranodal lymphomas to systemic chemotherapy. Cats with nasal lymphoma achieving a complete response after chemotherapy had a median survival time of 749 days.53 Collectively, these studies indicate that feline nasal lymphoma responds well to conventional treatment options, including radiation and systemic chemotherapy (Figures 7A & 7B).


Figure 7B. The cat in Figure 7A after treatment with megavoltage radiation therapy. Remarkable complete response is achieved with near normalization of facial conformation. (Image courtesy of Louis-Philippe de Lorimier, DVM, DACVIM [oncology].)
Even though there are few studies characterizing nonlymphoproliferative feline nasal tumors, the prognosis in cats with such tumors appears to be shorter than cats with nasal lymphoma. In a small pilot study of eight cats with nonlymphoproliferative nasal tumors treated with megavoltage radiation therapy, the median survival time was 382 days, which is similar to the prognosis in dogs with radiation-treated nasal tumors.54

SUMMARY

Nasal tumors in dogs and cats are usually a localized disease process, with low frequency of metastases. Early detection is often difficult because of the occult nature of nasal tumor development; however, timely therapeutic intervention is important to minimize extensive invasion into neighboring structures, including the central nervous system and orbital cavities. The standard of care for definitive treatment of nasal tumors confined to the nasal cavity in dogs and cats is radiation therapy alone or radiation therapy combined with surgery or chemotherapy. Although initially responsive to conventional radiation therapy allowing for long-term disease control, most dogs and cats eventually experience locally recurrent disease. With the greater availability of sophisticated radiation delivery units for use in veterinary medicine, including IMRT and stereotactic radiosurgery, it is likely that these advanced radiation delivery methods will improve management and treatment strategies for nasal tumors in dogs and cats in the near future.

Zachary L. Neumann, DVM*
Timothy M. Fan, DVM, PhD, DACVIM (internal medicine, oncology)
Department of Veterinary Clinical Medicine
College of Veterinary Medicine
University of Illinois
Urbana, IL 61802

Jayme Looper, DVM, DACVR (radiation oncology)
VCA Aurora Animal Hospital
2600 West Galena Blvd
Aurora, IL 60506

*Current address: Department of Clinical Sciences
College of Veterinary Medicine
University of Minnesota
St. Paul, MN 55108


ADVERTISEMENT

Source: VETERINARY MEDICINE,
Click here