Long-term outcomes of dogs undergoing surgical resection of mast cell tumors and soft tissue sarcomas: A prospective 2-year-long study

Eyelid and conjunctival mast cell tumors: A retrospective study of 26 dogs and 8 cats

OBJECTIVE

The objective of the study was to describe clinical and histologic characteristics of eyelid (LMCT) and conjunctival (CMCT) mast cell tumors in dogs and cats presented to a referral clinic in Germany.

ANIMAL STUDIED

Medical records were reviewed to identify dogs and cats diagnosed with LMCTs or CMCTs between 2006 and 2020.

RESULTS

LMCT were diagnosed in 31 patients and were cutaneous (n = 28; 20 dogs and 8 cats) or subcutaneous (three dogs). Five cases involved the mucocutaneous junction (four dogs, one cat). CMCTs occurred only in dogs (n = 3). At the time of presentation two of the four canine LMCT cases involving the mucocutaneous junction had metastasized to a mandibular lymph node. When applying the Kiupel system, both these cases were categorized as high grade. 85.7% (18/21) of the canine (19 cutaneous and 2 subcutaneous) LMCT and all CMCT cases were categorized as Kiupel low grade. No local recurrences occurred in all LMCT cases in which clean surgical margins were obtained (n = 18, mean surgical margin width: dogs 9.4 mm, cats 3.8 mm). Two cats (2/4) and four dogs (4/7) with questionable or incomplete surgical margins experienced local recurrences (mean time to recurrence of 180 and 637 days in dogs and cats, respectively).

CONCLUSION

Recurrence of low-grade LMCTs and CMCTs following excision with clean margins is rare. Tumors involving the mucocutaneous junction may be of higher grade and prone to lymphatic metastasis.

Weishaar's classification system for nodal metastasis in sentinel lymph nodes: Clinical outcome in 94 dogs with mast cell tumor

BACKGROUND

The therapeutic role and prognostic relevance of lymphadenectomy in mast cell tumor (MCT) has historically been evaluated on regional rather than sentinel lymph nodes.

HYPOTHESIS/OBJECTIVES

To update information about the association of histological nodal (HN) classes with clinical outcome in dogs with MCT after tumor excision and extirpation of normal-sized sentinel nodes (SLN) guided by radiopharmaceutical.

ANIMALS

Ninety-four dogs with histologically-confirmed treatment-naïve MCT (71 cutaneous, 22 subcutaneous and 1 conjunctival MCT) were included if without: distant metastases, lymphadenomegaly, concurrent mixed cutaneous, and subcutaneous MCT.

METHODS

This was a monoistitutional cohort study. Tumors characteristics were retrieved and SLNs were classified according to Weishaar's system. Incidence of MCT-related events (local, nodal, distant relapse), de novo MCT or other tumors and death (MCT-related and non-MCT-related), were recorded. Incidence curves were compared among the HN classes.

RESULTS

Twenty-seven dogs had HN0, 19 HN1, 37 HN2, and 11 HN3 SLN. Thirteen (2 HN0, 4 HN2, and 7 HN3) received adjuvant chemotherapies. Kiupel high grade, increasing number of SLN and lymphocentrums were associated with higher HN classes. Five dogs died for MCT-related causes: 1 low-grade (HN0) and 1 subcutaneous (HN3) had a local relapse, 2 high-grade had distant relapse (HN3-HN0) and 1 dog developed disease progression from a de novo subcutaneous MCT. No nodal relapse was registered. Fourteen dogs developed de novo MCTs.

CONCLUSION/DISCUSSION

Low grade/low-risk MCT with nonpalpable and normal sized SLN have a favorable outcome independently from the HN. Result should be considered strictly related to the successful SLN detection guided pre- and intraoperative by radiopharmaceutical markers.

Evaluating the relevance of surgical margins. Part one: The problems with current methodology

The goal of cancer surgery is to achieve a "clean" microscopic resection, with no residual tumour remaining in the wound. To achieve that goal, the surgeon typically incorporates a measured buffer of grossly normal tissue about the entire circumference of the tumour. Microscopic analysis of the resection boundaries is then performed to determine if all traces of the tumour have been completely removed. This analysis is thought to provide a surrogate indication as to the likelihood for that tumour to recur after surgery. However, it is recognised that tumour recurrence may not occur even when microscopic evidence of tumour has been identified at the resection margins, and recurrence can also occur when conventional histology has considered the tumour to have been completely removed. The explanations for this dichotomy are numerous and include technical and practical limitations of the processing methodology, and also several surgeon-related and tumour-related reasons. Ultimately, the inability to confidently determine when a tumour has been removed sufficiently to prevent recurrence can impact on the ability to provide owners with confident treatment advice. In this article, the authors describe the challenges with defining the true extent of the tumour margin from the perspective of the surgeon, the pathologist and the tumour. The authors also provide an analysis of why our current efforts to ensure that all traces of the local tumour have been successfully removed may provide an imperfect assessment of the risk of recurrence.

Safety and feasibility of short course pre-operative radiation therapy followed by surgical excision for canine solid tumours

Surgical resection of solid tumours, especially in early stages of disease, remains a cornerstone of cancer treatment in dogs and cats. There are numerous publications that show a strong association between local tumour control and outcome. To achieve local control in some cases radiation therapy and surgery are combined, with radiation therapy being delivered in the neoadjuvant or adjuvant setting. The objective of the study was to report acute toxicity and surgical site complication data in dogs that received a short-course pre-operative (SCPO) radiation therapy protocol, followed by surgical excision for various solid tumours. Medical records were reviewed, and data was analysed retrospectively. Dogs were included if a dermal or subcutaneous solid tumour was treated with SCPO radiation therapy and then was resected on the last day of radiation or 2-3 weeks later. A total of 34 dogs with 35 primary tumours were included. Acute radiation toxicity was diagnosed in 14 sites (40%). VRTOG scores were grade 1 in 50%, grade 2 in 43%, and grade 3 in 7%. Surgical site complications were identified in 17% of dogs with an overall surgical site infection rate of 11%. According to the Clavien-Dindo classification, two dogs required medical intervention (grade 2), 1 dog required surgical intervention under general anaesthesia (grade 3b), and 1 dog died as a result of complications (grade 5). Logistic regression analysis found that anatomic site was significantly associated with complications, where tumours located on the extremity was protective (P = .02; OR 0.06).

Defining the relevance of surgical margins. Part two: Strategies to improve prediction of recurrence risk

Due to the complex nature of tumour biology and the integration between host tissues and molecular processes of the tumour cells, a continued reliance on the status of the microscopic cellular margin should not remain our only determinant of the success of a curative-intent surgery for patients with cancer. Based on current evidence, relying on a purely cellular focus to provide a binary indication of treatment success can provide an incomplete interpretation of potential outcome. A more holistic analysis of the cancer margin may be required. If we are to move ahead from our current situation - and allow treatment plans to be more intelligently tailored to meet the requirements of each individual tumour - we need to improve our utilisation of techniques that either improve recognition of residual tumour cells within the surgical field or enable a more comprehensive interrogation of tumour biology that identifies a risk of recurrence. In the second article in this series on defining the relevance of surgical margins, the authors discuss possible alternative strategies for margin assessment and evaluation in the canine and feline cancer patient. These strategies include considering adoption of the residual tumour classification scheme; intra-operative imaging systems including fluorescence-guided surgery, optical coherence tomography and Raman spectroscopy; molecular analysis and whole transcriptome analysis of tissues; and the development of a biologic index (nomogram). These techniques may allow evaluation of individual tumour biology and the status of the resection margin in ways that are different to our current techniques. Ultimately, these techniques seek to better define the risk of tumour recurrence following surgery and provide the surgeon and patient with more confidence in margin assessment.

Optical coherence tomography for surgical margin evaluation of excised canine cutaneous and subcutaneous tumours

Currently, intraoperative tumour margin imaging is not routinely utilized in veterinary medicine. Optical coherence tomography (OCT) allows for real-time assessment of tissue morphology of 1-2 mm depth. The aims of this study were (1) to compare the histologic and OCT features of excised canine skin and subcutaneous specimens, and (2) to determine the diagnostic accuracy of OCT for surgical margin evaluation. The authors hypothesized that OCT imaging would correlate well with histopathology and that OCT would be sensitive for detection of incomplete margins. Eighty dogs were prospectively enrolled. Tumours were excised, and the surgical margins were imaged using a spectral domain OCT system. The tumour type and completeness of excision were determined by histopathology. Nine blinded observers received training in OCT image interpretation and were then given a set of OCT images and videos. The observers assigned each image/video a grade from 1 (no tumour) to 4 (tumour) and the results were compared to histopathology. The overall median sensitivity and specificity of OCT imaging for detection of incomplete margins were 86.7% and 84.6%, respectively. A potential limitation is that observers had varied experience with OCT image interpretation, ranging from no prior experience to participating in a previous OCT project. OCT is sensitive for detection of incomplete margins and could be a promising real-time surgical margin imaging modality. Further study is needed to evaluate intraoperative applications of OCT and its impact on tumour recurrence and long-term outcome.

Treatment of canine and feline sarcoma using MR-guided focused ultrasound system

PURPOSE

In recent years, veterinary medicine has enhanced its applications beyond traditional approaches, progressively incorporating the Focused Ultrasound (FUS) technology. This study investigated the ability of FUS to precisely ablate naturally occurring canine and feline soft tissue sarcomas (STS).

METHODS

Six dogs and four cats with superficial tumours were enrolled in the study. The tumours were treated with a Magnetic Resonance guided FUS (MRgFUS) robotic system featuring a single element spherically focused transducer of 2.6 MHz. The tumours were then removed by surgery and sent for hematoxylin and eosin (H&E) staining.

RESULTS

The MRgFUS system was capable of inflicting well-defined overlapping lesions in the tumours. The anatomical sites of the treated tumours were the neck, leg, face, back and belly. Coagulative necrosis was evidenced by histopathology assessment in 80% of cases.

CONCLUSION

Therefore, this technology can be a therapeutic solution for veterinary cancer and a model for advancing the knowledge on human STS.

Evaluation of Tumor Grade and Proliferation Indices before and after Short-Course Anti-Inflammatory Prednisone Therapy in Canine Cutaneous Mast Cell Tumors: A Pilot Study

Glucocorticoid administration is a common clinical practice that attempts to decrease the inflammation associated with and improve the resectability of canine mast cell tumors (MCTs). However, the impact of neoadjuvant glucocorticoids on the histological features and proliferation indices of canine MCTs is unknown. The objective of this study was to evaluate changes in tumor grade, mitotic count, Ki67, AgNOR, and AgNORxKi67 scores following short-course anti-inflammatory neoadjuvant prednisone in canine patients with MCTs. This was a prospective single-arm pilot study. Client-owned dogs with treatment-naïve cytologically confirmed MCTs were enrolled. Patients underwent an initial incisional biopsy followed by a 10–14-day course of anti-inflammatory prednisone and surgical resection. All histological samples were randomized, masked, and evaluated by a single pathologist. Unstained paired pre- and post-treatment samples were submitted to a commercial laboratory for Ki67 and AgNOR immunohistochemical analysis. There were 11 dogs enrolled with 11 tumors. There were no statistical differences between the pre- and post-treatment histological parameters of mitotic index, Ki67, AgNOR, or Ki67xAgNOR. There were no clinically significant alterations between pre-treatment and post-treatment in the assignment of tumor grades. A short course of anti-inflammatory prednisone does not appear to alter the histological parameters that affect grade determination or significantly alter the proliferation indices in canine MCTs.

Diagnosis, Prognosis and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors

Mast cell tumors (MCTs) are hematopoietic neoplasms composed of mast cells. It is highly common in dogs and is extremely important in the veterinary oncology field. It represents the third most common tumor subtype, and is the most common malignant skin tumor in dogs, corresponding to 11% of skin cancer cases. The objective of this critical review was to present the report of the 2nd Consensus meeting on the Diagnosis, Prognosis, and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors, which was organized by the Brazilian Association of Veterinary Oncology (ABROVET) in August 2021. The most recent information on cutaneous and subcutaneous mast cell tumors in dogs is presented and discussed.

Tigilanol Tiglate-Mediated Margins: A Comparison With Surgical Margins in Successful Treatment of Canine Mast Cell Tumours

Tigilanol tiglate (TT) is a novel small molecule registered as a veterinary pharmaceutical for intratumoural treatment of canine mast cell tumours (MCTs). The drug has a multifactorial mode of action resulting in rapid destruction of the treated tumour by haemorrhagic necrosis and subsequent slough of the necrotic tumour to reveal a tissue deficit that is left to heal by second intention with minimal to no veterinary intervention. Here we introduce the concept of TT-mediated margins, the calculated margin of tissue loss analogous to surgically applied margins to help clinicians conceptualise tissue deficits formed following tumour destruction by TT relative to surgical excision. We used data from 51 dogs that were recurrence-free 12 months after a single administered TT dose into a single target MCT <10 cm³ in volume in a randomised, controlled clinical trial in the USA. We calculated TT-mediated margins based on length of the longest axis of (i) the tumour prior to treatment and (ii) the maximum tissue deficit formed 7–14 days after TT treatment. We compared these TT-mediated margins for each tumour to two surgical approaches to MCT excision in general practise: modified proportional margins (with 2 cm upper limit) and 3 cm fixed margins. For most dogs, TT-mediated margins were less than half the length of the margins calculated for the two surgical approaches in removing the same tumour. There was a trend for TT-mediated margins to increase with increasing tumour volume. Nonetheless, even for the larger tumours in this study (>2 cm³ volume), 50% of TT-mediated margins were less than half the length of the two surgical margins. Eighteen cases were lower limb MCTs, sites often surgically challenging in veterinary practise. On these lower limbs, TT-mediated margins were less than half the length of the corresponding proportional margins in 56% of cases and larger than proportional margins in only two cases. This study suggests that, in many cases, smaller and more targeted margins could be expected when treating MCTs <10 cm³ volume with TT compared with surgical excision. TT-mediated margins are a novel approach to conceptualise tissue deficits after intratumoural TT treatment.

Outcomes of adjunctive radiation therapy for the treatment of mast cell tumors in dogs and assessment of toxicity: A multicenter observational study of 300 dogs

Background

Radiation therapy is commonly used as an adjunct to incomplete surgical excision in dogs with mast cell tumors (MCT), but the optimal dose and fractionation regimen have yet to be determined.

Hypothesis

We assessed outcomes (time to local recurrence, patient survival and toxicity) of a large population of dogs with MCT that received adjunctive radiation therapy.

Animals

Three hundred dogs with 302 MCT treated using adjunctive radiation therapy.

Methods

Retrospective observational study. Clinical records of 4 veterinary radiation centers were reviewed.

Results

Local recurrence rates were similar regardless of radiation protocol with 6.6% of patients developing recurrent cutaneous MCT at a median of 526 days. Local recurrence rate was similar between high and low‐risk MCT. Mast cell tumor related death was reported in 19% of all dogs, with 13% of dogs with low‐risk MCT dying of their disease compared to 29% of dogs with high‐risk MCT. No SC MCT (SCMCT) recurred after radiation therapy and only 7% of dogs with SCMCT were reported to have died of their disease. Mild late toxicity was common in both protocols and severe late toxicity occurred in 1.9% of dogs many years after treatment.

Conclusions and Clinical Importance

Our study supports the use of adjunctive radiation for the long‐term control of incompletely or narrowly excised cutaneous and SCMCT in dogs. More moderate dose and fractionation protocols may be appropriate in the adjunctive treatment of low‐risk MCT in dogs. Large multicenter prospective studies are required to establish the optimal dose and fractionation for MCT of different risk categories.

Intersurgeon agreement in determining 3 cm surgical margins of subcutaneous tumors in dogs

OBJECTIVE

To evaluate intersurgeon agreement in performing a 3 cm wide surgical excision for subcutaneous malignancies in dogs.

STUDY DESIGN

Prospective, blinded, randomized, clinical study.

ANIMALS

Client-owned dogs with subcutaneous tumors undergoing curative-intent, wide surgical excision between April 2019 to March 2020.

METHODS

Four surgeons, instructed to perform a 3 cm wide excision, each sequentially indicated their proposed skin incision locations around subcutaneous tumors, without knowledge of the other surgeons' proposed incisions. A tripod-mounted camera and laser positioning system were used to photograph each surgeon's proposed margin length. A random-effects model was used to estimate the standard deviation of margin lengths that would be expected from a random sample of surgeons.

RESULTS

Each of the four surgeons provided 33 independent radial measurements from 11 tumors (six soft tissue sarcomas and five mast cell tumors), for a total of 132 radial measurements. No individual surgeon consistently proposed longer or shorter margin incision locations. The prediction interval for a future margin measurement was 6 mm, implying that the 95% confidence interval of an individual surgeon's margin length would be within ±6 mm of the mean margin length from a random sample of surgeons.

CONCLUSION

Ninety-five percent of surgeons would be expected to deliver a surgical dose between 2.4-3.6 cm, for a theoretically uniform surgical dose of 3 cm wide margins.

CLINICAL SIGNIFICANCE

Surgical doses are likely to vary at clinically relevant levels among surgeons, complicating design and interpretation of studies attempting to identify an ideal surgical dose.

Surgical Margins in Canine Cutaneous Soft-Tissue Sarcomas: A Dichotomous Classification System Does Not Accurately Predict the Risk of Local Recurrence

Simple Summary

Histological evaluation of surgical margins is crucial for correct prognostication and adjuvant treatment recommendation after excision of soft tissue sarcoma (STS) in dogs. Incompletely excised STS have a high risk of local recurrence (LR), while completely excised STS without other negative prognostic factors are generally associated with a good prognosis. However, guidelines are lacking on how to manage STS excised with clean but close margins (CbCM), although some authors advocated their inclusion in the tumor-free margin group. This retrospective study investigates the impact of CbCM on LR of canine STS. Ninety-eight surgical excised canine STS at first presentation were included. Cumulative incidence of LR was estimated for each category of margins (tumor-free, infiltrated, CbCM), and after grouping CbCM alternatively in the tumor-free and infiltrated category. Cumulative incidence of LR at three years differed significantly between the three categories, and it was estimated to be 42% with infiltrated margins, 23% with CbCM, 7% with tumor-free margins. Both when CbCM were grouped with infiltrated margins or with tumor-free margins, the incidence of LR was statistically different. The rate of LR with CbCm was greater than with tumor-free margins. The category CbCM may be considered as a separate prognostic category.

Abstract

Adjuvant treatments are recommended in dogs with incompletely excised cutaneous soft-tissue sarcoma (STS) to reduce the risk of local recurrence (LR), although guidelines are lacking on how to manage clean but close margins (CbCM). This retrospective study investigates the impact of CbCM on LR of canine STS. Ninety-eight surgically excised canine STS at first presentation were included. Tissue samples were routinely trimmed and analyzed. Cumulative incidence of LR was estimated for each category of margins (tumor-free, infiltrated, CbCM), and included CbCM in the tumor-free and infiltrated category, respectively. The prognostic impact on LR was then adjusted for relevant prognostic factors. Cumulative incidence of LR at three years differed significantly between the three categories (p = 0.016), and was estimated to be 42% with infiltrated margins, 23% with CbCM, 7% with tumor-free margins. Both when CbCM were grouped with infiltrated margins (p = 0.033; HR = 5.05), and when CbCM were grouped with tumor-free margins (p = 0.011; HR = 3.13), a significant difference between groups was found. STS excised with infiltrated margins had the greatest risk of LR. The rate of LR with CbCm was greater than recurrence rate of tumor-free margins. The category CbCM may be considered as a separate prognostic category.

Prognostic impact of clinical, haematological, and histopathological variables in 102 canine cutaneous perivascular wall tumours

Identification of prognostic factors for perivascular wall tumours (PWTs) is desirable to accurately predict prognosis and guide treatment. 100 and two dogs with surgically excised PWTs without distant metastasis were retrospectively enrolled in this multi-institutional study, and the impact of pre-treatment leukocyte parameters, clinical and histopathological variables on local recurrence (LR) and overall-survival time (OST) were evaluated. Increasing values of white blood cell count (WBCC), neutrophil count (NC) and neutrophil-to-lymphocyte ratio (NLR) were significantly correlated with the hazard of LR in univariate analysis. WBCC and NC remained prognostic when adjusted for margins, grade, tumour size, location and skin ulceration, but lost their significance when adjusted for mitotic index and necrosis, whilst NLR remained prognostic only when close margins where categorised as infiltrated. Castrated males had a higher hazard of LR than intact males in univariate analysis, but significance was lost in multivariate models. Ulcerated PWTs and those located on the distal extremities had a higher hazard of LR both in univariate and multivariate analysis. Histological grade, necrosis, mitotic count, and infiltrated margins were all associated with LR both in univariate and multivariate analysis. Boxer breed, older age, ulceration, grade III, necrosis >50% and higher mitotic count were correlated with shorter OST, although breed and age lost their significance in multivariate analysis. Prognostication of surgically excised PWTs should be based on both clinical and histopathological variables. If validated in further studies, leukocyte counts and NLR may aid the clinician in identifying dogs at higher risk of LR before treatment.

Evaluation of a modified proportional margin approach for complete surgical excision of canine cutaneous mast cell tumours and its association with clinical outcome

Canine cutaneous mast cell tumours (MCTs) represent a common neoplasm in veterinary practice. Several reported techniques are available to guide surgical excision. Our study examined one hundred cutaneous MCTs that were excised surgically using a modified proportional margin approach. A 2 cm lateral margin upper limit was applied for any tumour diameter that exceeded this size with a deep surgical margin of one fascial plane applied. A retrospective, cross-sectional study with follow-up was used to determine the clinical utility of this excision technique. Associations between explanatory variables of tumour size and grade were compared with outcomes of complete excision and size of histologic tumour-free margins (HTFM) using the appropriate Pearson's χ² and Fisher's exact tests. Follow-up data evaluated tumour recurrence and patient survival. Ninety-five percent of MCTs (95/100) were completely excised. No significant association in the achievement of complete excision between low- and high-grade MCTs (P = .48) was noted. Tumour size was not associated with the rate of complete excision (P = .06). Tumour grade and size did not influence the size of the HTFM (P = .94 and P = .14, respectively). Overall, a recurrence rate of 3% (3/100 tumours) and de novo MCT development rate of 7.7% (5/65 dogs) was noted, with median follow-up period of 593 days (range 180-1460 days). Post-operative metastases were seen in 4.6% of dogs (3/65). Therefore, a modified proportional margin approach with 2 cm lateral margin upper limit is a suitable technique to guide surgical excision of canine cutaneous MCTs.

Randomized controlled clinical study evaluating the efficacy and safety of intratumoral treatment of canine mast cell tumors with tigilanol tiglate (EBC-46)

Objective

To evaluate the efficacy and safety of tigilanol tiglate (TT) for local intratumoral treatment of mast cell tumors (MCTs) in dogs.

Methods

A randomized controlled clinical study in 2 phases involving 123 dogs with cytologically diagnosed MCT. Phase 1 compared 81 TT‐treated dogs with 42 control dogs; phase 2 allowed TT treatment of control dogs and retreatment of dogs that failed to achieve tumor resolution after TT treatment in phase 1. Tigilanol tiglate (1 mg/mL) was injected intratumorally with dose based on tumor volume. Concomitant medications were used to minimize potential for MCT degranulation. Modified response evaluation criteria in solid tumors were used to evaluate treatment response at 28 and 84 days. Adverse events and quality of life were also assessed.

Results

A single TT treatment resulted in 75% complete response (CR) (95% confidence interval [CI] = 61‐86) by 28 days, with no recurrence in 93% (95% CI = 82‐97) of dogs by 84 days. Eight TT‐treated dogs that did not achieve CR in phase 1 achieved CR after retreatment, increasing the overall CR to 88% (95% CI = 77‐93). Control dogs had 5% CR (95% CI = 1‐17) at 28 days. Wound formation after tumor slough and wound size relative to tumor volume were strongly associated with efficacy. Adverse events typically were low grade, transient, and directly associated with TT's mode of action.

Conclusions

Tigilanol tiglate is efficacious and well tolerated, providing a new option for the local treatment of MCTs in dogs.

Histologically low-grade, yet biologically high-grade, canine cutaneous mast cell tumours: A systematic review and meta-analysis of individual participant data

Low-grade canine cutaneous mast cell tumour (cMCT) with metastasis at the time of treatment is uncommonly reported, with few studies focusing on this specific clinical entity. The specific objective of this study was to systematically review the veterinary literature and perform a meta-analysis summarizing the clinical presentation, treatments reported and clinical outcomes from dogs with histologically low-grade cMCT and metastasis present at initial treatment. A total of 980 studies were screened with eight publications providing data on 121 dogs ultimately included. The most common treatments were surgery with adjuvant chemotherapy in 83/121 (69%) dogs; combined surgery, radiation and chemotherapy in 17/121 (14%) dogs; chemotherapy alone in 12/121 (10%) dogs and surgery alone in 7/121 (6%) dogs. Dogs with distant metastasis (n = 22) experienced significantly shorter survival compared with those with regional lymph node (RLN) metastasis (n = 99; median 194 vs 637 days; P < .01). Two variables were significantly associated with increased risk of death: presence of distant (vs RLN) metastasis (hazard ratio = 2.60; P < .01) and not receiving surgery as a component of treatment (hazard ratio = 3.79; P < .01). Risk of bias was judged to be low in terms of selection and performance bias but high in terms of detection and exclusion bias. In conclusion, dogs with cMCT and RLN metastasis can be expected to live significantly longer than those with distant metastasis, and surgery appears to have a role in extending survival of metastatic low-grade cMCT.

Ultrasound is a poor predictor of early or overt liver or spleen metastasis in dogs with high-risk mast cell tumours

Conflicting evidence exists regarding the importance of routine abdominal ultrasound (US) with hepatic and splenic fine needle aspiration (FNA) cytology during staging of canine mast cell tumours (MCT). The objective of this study was to correlate ultrasonographic and cytologic findings in dogs with strictly defined high-risk MCTs and to determine the influence on outcome. Our hypothesis was that US poorly predicts visceral metastasis in high-risk MCTs and that early metastasis is associated with improved outcome when compared to overt metastasis. US of liver and spleen correlated to cytologic results, categorized as no metastasis, early metastasis or overt metastasis. Of 82 dogs prospectively enrolled, 18% had early visceral metastasis and 7% had overt metastasis on cytology; 67% with visceral metastasis had regional LN metastasis. US was a poor predictor of metastasis with sensitivity, specificity, positive predictive value and negative predictive value for the spleen of 67%, 68%, 21% and 94%, respectively and for the liver of 29%, 93%, 56% and 82%, respectively. Median time to progression (TTP) for dogs with no metastasis, early metastasis and overt metastasis was not reached, 305 and 69 days, respectively (P < .001). Median survival time (MST) for the 3 groups were not reached, 322 and 81 days, respectively (P < .001). High Patnaik or Kiupel grade, early metastasis, overt metastasis and adequate local control were significantly associated with outcome. Early visceral metastasis was associated with poorer outcome compared to dogs without metastasis, however, a subset of dogs experienced long-term control.