Four-fraction radiation therapy for macroscopic soft tissue sarcomas in 16 dogs

Update in Veterinary Radiation Oncology: Focus on Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) involves the precise delivery of highly conformal, dose-intense radiation to well-demarcated tumors. Special equipment and expertise are needed, and a unique biological mechanism distinguishes SRT from other forms of external beam radiotherapy. Families find the convenient schedules and minimal acute toxicity of SRT appealing. Common indications in veterinary oncology include nasal, brain, and bone tumors. Many other solid tumors can also be treated, including spinal, oral, lung, heart-base, liver, adrenal, and prostatic malignancies. Accessibility of SRT is improving, and new data are constantly emerging to define parameters for appropriate case selection, radiation dose prescription, and long-term follow-up.

A review of the development of histotripsy for extremity tumor ablation with a canine comparative oncology model to inform human treatments

Cancer is a devasting disease resulting in millions of deaths worldwide in both humans and companion animals, including dogs. Treatment of cancer is complex and challenging and therefore often multifaceted, as in the case of osteosarcoma (OS) and soft tissue sarcoma (STS). OS predominantly involves the appendicular skeleton and STS commonly develops in the extremities, resulting in treatment challenges due to the need to balance wide-margin resections to achieve local oncological control against the functional outcomes for the patient. To achieve wide tumor resection, invasive limb salvage surgery is often required, and the patient is at risk for numerous complications which can ultimately lead to impaired limb function and mobility. The advent of tumor ablation techniques offers the exciting potential of developing noninvasive or minimally invasive treatment options for extremity tumors. One promising innovative tumor ablation technique with strong potential to serve as a noninvasive limb salvage treatment for extremity tumor patients is histotripsy. Histotripsy is a novel, noninvasive, non-thermal, and non-ionizing focused ultrasound technique which uses controlled acoustic cavitation to mechanically disintegrate tissue with high precision. In this review, we present the ongoing development of histotripsy as a non-surgical alternative for extremity tumors and highlight the value of spontaneously occurring OS and STS in the pet dog as a comparative oncology research model to advance this field of histotripsy research.

Description and efficacy of a response-based "QUAD" cyclical hypofractionated palliative-intent radiation protocol in dogs with macroscopic solid tumours: 108 cases

Palliative-intent radiation therapy can alleviate pain and clinical signs in dogs with cancer, but optimal fractionation scheme is unknown. The objective of this retrospective case series is to evaluate clinical benefit, objective response, adverse effects, and outcomes in 108 dogs with macroscopic solid tumours treated with a cyclical "QUAD" hypofractionated palliative-intent radiation therapy protocol. Median QUAD dose was 14 Gy (14-16 Gy). Median total dose was 28 Gy (14-48 Gy). Clinical benefit rate was 93%, with median onset of subjective palliation 21 days after the first QUAD, lasting a median of 134 days. Tumour volumetric objective response was assessed with CT prior to the third QUAD in 36 dogs, with stable disease in 24 dogs (67%) and partial response in 9 dogs (25%). Sinonasal and oral were the most common tumour locations in 32 and 30 dogs, respectively. Median progression-free survival was 153 days (95% CI 114-200). Median overall survival was 212 days (95% CI 152-259). Number of QUAD cycles completed, clinical benefit achieved, anti-inflammatory received, total radiation dose, time to maximum clinical benefit, and response duration were positively associated with progression-free and overall survival. Acute toxicities were observed in 15 dogs (14%) with 3 high-grade (grade 3) toxicities (3%). Low-grade (grade 1 and 2) late skin and ocular toxicities were observed in 31 dogs (29%), predominantly leukotrichia, alopecia, keratoconjunctivitis sicca, and cataracts. This report demonstrates that QUAD radiation is an alternative protocol to be considered for palliation of dogs with inoperable or advanced stage solid tumours.

Pilot study evaluating the tolerability of a 3 Gy × 10 daily fraction 3D-conformal palliative radiation therapy protocol plus toceranib for the treatment of measurable carcinomas in the dog

The use of radiation therapy in conjunction with small molecule inhibitors is an appealing treatment combination for non-resectable carcinomas, which tend to be locally invasive with variable risk of locoregional metastasis. This prospective, pilot study aimed to evaluate the tolerability and adverse event profile of concurrent toceranib and palliative-intent radiation therapy (PRT) in dogs with measurable carcinoma and to secondarily evaluate short-term measurable tumor response. Fifteen dogs with measurable carcinoma received toceranib and 3D-conformal PRT in 3 Gy/fraction for 10 daily fractions. Adverse events were graded using standard schemes and tolerability was followed via quality-of-life questionnaires during the 12-week treatment period. Thirteen dogs (87%) experienced acute radiation toxicity, graded as severe in three dogs. All dogs experienced toceranib toxicity, graded as severe in one dog. Seven dogs (47%) completed the 12-week study protocol; four were withdrawn due to toxicity and/or associated poor quality of life and four developed progressive disease. Based on these preliminary results, this 3D-conformal chemoradiation protocol should be considered with caution and only with proper owner education on potential toxicity. More conformal treatment planning techniques or alternative protocols should be investigated for improved tolerability.

Response of Canine Soft Tissue Sarcoma to Stereotactic Body Radiotherapy

Canine soft tissue sarcoma (STS) has served as a preclinical model for radiation, hyperthermia, experimental therapeutics, and tumor microenvironmental research for decades. Stereotactic body radiotherapy (SBRT) demonstrates promising results for the control of various tumors in human and veterinary medicine; however, there is limited clinical data for the management of STS with SBRT. In this retrospective study, we aimed to define overall efficacy and toxicity of SBRT for the treatment of macroscopic canine STS to establish this preclinical model for comparative oncology research. Fifty-two canine patients met inclusion criteria. Total radiation dose prescribed ranged from 20-50 Gy delivered in 1-5 fractions. Median progression-free survival time (PFST) was 173 days and overall survival time (OST) 228 days. Best overall response was evaluable in 46 patients, with 30.4% responding to treatment (complete response n = 3; partial response n = 11). For responders, OST significantly increased to 475 days vs. 201 days (P = 0.009). Prognostic factors identified by multivariable Cox regressions included size of tumor and metastasis at presentation. Dogs were 3× more likely to progress (P = 0.009) or 3.5× more likely to experience death (P = 0.003) at all times of follow up if they presented with metastatic disease. Similarly, every 100-cc increase in tumor volume resulted in a 5% increase in the risk of progression (P = 0.002) and death (P = 0.001) at all times of follow up. Overall, 30.8% of patients developed acute toxicities, 7.7% grade 3; 28.8% of patients developed late toxicities, 11.5% grade 3. Increased dose administered to the skin significantly affected toxicity development. SBRT serves as a viable treatment option to provide local tumor control for canine macroscopic STS, particularly those with early-stage disease and smaller tumors. The results of this study will help to define patient inclusion criteria and to set dose limits for preclinical canine STS trials involving SBRT.

Stereotactic body radiation therapy for treatment of soft tissue sarcomas in 35 dogs

OBJECTIVE

To describe response rate, tumor progression, patient survival times, prognostic factors associated with tumor progression and patient survival times, and radiation toxicoses (acute and latent) in dogs treated with curative-intent stereotactic body radiation therapy (SBRT) for soft tissue sarcomas (STS).

ANIMALS

35 client-owned dogs with STS treated with curative-intent SBRT between October 2011 and May 2017.

PROCEDURES

Medical records were reviewed to identify dogs that underwent SBRT. Dogs with oral tumors, hemangiosarcoma, or histiocytic sarcoma were excluded. Data collected included patient-, STS-, and SBRT-related information, including follow-up information pertaining to tumor progression and patient survival time for ≥ 6 months, unless tumor progression or patient death occurred sooner.

RESULTS

Objective measurements allowing for evaluation of tumor response were available for 28 dogs, of which 13 (46%) had either a partial (10/28 [36%]) or complete (3/28 [11%]) response. Twenty-four dogs died, and the medians for progression-free survival time, time to progression of disease, overall survival time, and disease-specific survival time were 521, 705, 713, and 1,149 days, respectively. Low histologic grade and extremity locations of STSs were positive prognostic factors for patient survival times. Acute adverse effects were limited to skin, and 1 dog underwent limb amputation because of a nonhealing wound.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that SBRT for STS was well tolerated in most dogs and provided local tumor control. Additional studies are needed to determine the best SBRT protocol for treatment of STSs in dogs.

Sarcomas-A barren immunological wasteland or field of opportunity for immunotherapy?

Key advances in our understanding of immunobiology and the immunosuppressive mechanisms of the tumour microenvironment have led to significant breakthroughs in manipulating the immune system to successfully treat cancer. Remarkable therapeutic responses have occurred with tumours that carry a high mutational burden. In these cases, pre-existing tumour-specific T cells can be rejuvenated via checkpoint inhibition to eliminate tumours. Furthermore, durable remissions have been achieved in haematological malignancies following adoptive transfer of T cells that specifically target cell surface proteins where expression is restricted to the malignancy's cell of origin. Soft tissue sarcomas and bone sarcomas have a paucity of non-synonymous somatic mutations and do not commonly express known, targetable, tumour-specific antigens. Historically, soft tissue sarcomas have been considered immunologically 'cold' and as such, unlikely candidates for immune therapy. Here, we review the immune landscape of canine and feline sarcomas and the immunotherapeutic strategies that have been employed in veterinary clinical trials to improve patient outcome. We also provide insight into immunotherapeutic approaches being used to treat human sarcomas. Together, current data indicates that, rather than a barren immunological wasteland, sarcomas represent a field of opportunities for immunotherapies. Furthermore, we and others would suggest that strategic combinations of immunotherapeutic approaches may hold promise for more effective treatments for high grade soft tissue sarcomas and bone sarcomas.

Canine sarcomas as a surrogate for the human disease

Pet dogs are becoming increasingly recognized as a population with the potential to inform medical research through their treatment for a variety of maladies by veterinary health professionals. This is the basis of the One Health initiative, supporting the idea of collaboration between human and animal health researchers and clinicians to study spontaneous disease processes and treatment in animals to inform human health. Cancer is a major health burden in pet dogs, accounting for approximately 30% of deaths across breeds. As such, pet dogs with cancer are becoming increasingly recognized as a resource for studying the pharmacology and therapeutic potential of anticancer drugs and therapies under development. This was recently highlighted by a National Academy of Medicine Workshop on Comparative Oncology that took place in mid-2015 (http://www.nap.edu/21830). One component of cancer burden in dogs is their significantly higher incidence of sarcomas as compared to humans. This increased incidence led to canine osteosarcoma being an important component in the development of surgical approaches for osteosarcoma in children. Included in this review of sarcomas in dogs is a description of the incidence, pathology, molecular characteristics and previous translational therapeutic studies associated with these tumors. An understanding of the patho-physiological and molecular characteristics of these naturally occurring canine sarcomas holds great promise for effective incorporation into drug development schemas, for evaluation of target modulation or other pharmacodynamic measures associated with therapeutic response. These data could serve to supplement other preclinical data and bolster clinical investigations in tumor types for which there is a paucity of human patients for clinical trials.

Outcomes of Spatially Fractionated Radiotherapy (GRID) for Bulky Soft Tissue Sarcomas in a Large Animal Model

GRID directs alternating regions of high- and low-dose radiation at tumors. A large animal model mimicking the geometries of human treatments is needed to complement existing rodent systems (eg, microbeam) and clarify the physical and biological attributes of GRID. A pilot study was undertaken in pet dogs with spontaneous soft tissue sarcomas to characterize responses to GRID. Subjects were treated with either 20 Gy (3 dogs) or 25 Gy (3 dogs), delivered using 6 MV X-rays and a commercial GRID collimator. Acute toxicity and tumor responses were assessed 2, 4, and 6 weeks later. Acute Radiation Therapy Oncology Group grade I skin toxicity was observed in 3 of the 6 dogs; none experienced a measurable response, per Response Evaluation Criteria in Solid Tumors. Serum vascular endothelial growth factor, tumor necrosis factor α, and secretory sphingomyelinase were assayed at baseline, 1, 4, 24, and 48 hours after treatment. There was a trend toward platelet-corrected serum vascular endothelial growth factor concentration being lower 1 and 48 hours after GRID than at baseline. There was a significant decrease in secretory sphingomyelinase activity 48 hours after 25 Gy GRID ( P = .03). Serum tumor necrosis factor α was quantified measurable at baseline in 4 of the 6 dogs and decreased in each of those subjects at all post-GRID time points. The new information generated by this study includes the observation that high-dose, single fraction application of GRID does not induce measurable reduction in volume of canine soft tissue sarcomas. In contrast to previously published data, these data suggest that GRID may be associated with at least short-term reduction in serum concentration of vascular endothelial growth factor and serum activity of secretory sphingomyelinase. Because GRID can be applied safely, and these tumors can be subsequently surgically resected as part of routine veterinary care, pet dogs with sarcomas are an appealing model for studying the radiobiologic responses to spatially fractionated radiotherapy.

Diagnostic value of neutrophil-lymphocyte and albumin-globulin ratios in canine soft tissue sarcoma

OBJECTIVE

To investigate the ability of neutrophil-to-lymphocyte ratio and albumin-to-globulin ratio to differentiate soft tissue sarcoma from benign soft tissue tumours.

METHODS

A retrospective study of pretreatment haematology and biochemistry in dogs diagnosed with soft tissue sarcoma or benign soft tissue tumours. The neutrophil-to-lymphocyte ratio and albumin-to-globulin ratio were compared between the two groups. In dogs diagnosed with soft tissue sarcoma, the relationship of neutrophil-to-lymphocyte ratio and albumin-to-globulin ratio to histological tumour grade (I to III) was assessed.

RESULTS

In the dogs with soft tissue sarcoma (n=22), the neutrophil-to-lymphocyte ratio was significantly increased and the albumin-to-globulin ratio decreased compared to those with benign soft tissue tumours (n=14). The neutrophil-to-lymphocyte ratio and albumin-to globulin ratio were not useful as predictors of tumour grade in dogs diagnosed with soft tissue sarcoma.

CLINICAL SIGNIFICANCE

Pretreatment neutrophil-to-lymphocyte ratio and albumin-to globulin ratio may aid with diagnosis and optimal treatment planning. Further investigation into their prognostic implications is warranted.

HYPOFRACTIONATED RADIOTHERAPY FOR MACROSCOPIC CANINE SOFT TISSUE SARCOMA: A RETROSPECTIVE STUDY OF 50 CASES TREATED WITH A 5 × 6 GY PROTOCOL WITH OR WITHOUT METRONOMIC CHEMOTHERAPY

Wide surgical resection or a marginal/incomplete resection followed by full-course radiation therapy is the current standard of care for canine soft tissue sarcoma. The purpose of this retrospective, descriptive, bi-institutional study was to determine the effectiveness and toxicity of a hypofractionated 5 × 6 Gy protocol on macroscopic canine soft tissue sarcoma in terms of progression-free interval (PFI) and overall survival (OS), and to identify prognostic factors for patient outcome. Dogs with macroscopic soft tissue sarcoma irradiated with 5 × 6 Gy were eligible for the study. Progression-free interval and OS were compared with respect to different tumor and patient characteristics by the Kaplan-Meier method and multivariable Cox regression analysis. Fifty dogs with macroscopic disease were included. All dogs received the same radiation therapy protocol; part of the group (n = 20) received postradiation metronomic chemotherapy. Median PFI for all cases was 419 days (95% confidence interval (CI): 287-551) and median OS was 513 days (95% CI: 368-658). Dogs with tumors on the limbs had significantly longer PFI and OS, compared with head or trunk. Increasing tumor burden decreased OS. The addition of metronomic chemotherapy yielded a significantly longer OS (757 days (95% CI: 570-944) compared with dogs that did not receive systemic treatment (286 days (95% CI: 0-518), (P = 0.023)), but did not influence progression-free interval. Toxicity was low throughout all treatments. The 5 × 6 Gy radiation therapy protocol was well tolerated and provided long PFI and OS in dogs with macroscopic soft tissue sarcoma.

Palliative radiation therapy outcomes for cats with oral squamous cell carcinoma (1999-2005)

Squamous cell carcinoma (SCC) accounts for approximately 10% of all feline tumors. The purpose of this retrospective study was to describe outcomes for a group of cats with oral SCC that were treated with palliative radiation therapy. Fifty-four cats met the inclusion criteria of nonresectable, oral SCC treated with coarse fractionated megavoltage (MeV) radiation therapy. Radiation therapy for all cats was delivered with a 6 MeV linear accelerator. Total radiation doses of 24 Gray to 40 Gray were administered in three to four fractions, once-per-week over 4 to 5 weeks. Concurrent chemotherapy protocols varied and were administered at the discretion of the clinician and client. Forty-nine patients completed the planned treatment protocols. Overall mean and median survival times for cats completing the planned treatment protocols were 127 and 92 days (n = 49). Mean and median survival times of cats receiving palliative radiation therapy alone were 157 and 113 days (n = 12). Mean and median survival times of patients receiving both radiation therapy and chemotherapy were 116 and 80 days (n = 37). Patients with sublingual tumors had a median survival time of 135 days (n = 15), compared to mandibular tumors that had a median survival time of 80 days (n = 26). For the majority of patients that completed the planned treatment protocol (65%), owners reported a subjectively improved quality of life. Findings from this uncontrolled study supported the use of palliative radiation therapy for cats with nonresectable oral squamous cell carcinoma.

The effect of interleukin-2 on canine peripheral nerve sheath tumours after marginal surgical excision: a double-blind randomized study

Background

The objective of this study was to evaluate the effect on outcomes of intraoperative recombinant human interleukin-2 injection after surgical resection of peripheral nerve sheath tumours. In this double-blind trial, 40 patients due to undergo surgical excision (<5 mm margins) of presumed peripheral nerve sheath tumours were randomized to receive intraoperative injection of interleukin-2 or placebo into the wound bed.

Results

There were no significant differences in any variable investigated or in median survival between the two groups. The median recurrence free interval was 874 days (range 48–2141 days), The recurrence-free interval and overall survival time were significantly longer in dogs that undergone the primary surgery by a specialist-certified surgeon compared to a referring veterinarian regardless of whether additional adjunct therapy was given.

Conclusion

Overall, marginal excision of peripheral nerve sheath tumours in dogs resulted in a long survival time, but adjuvant treatment with recombinant human interleukin-2 (rhIL-2) did not provide a survival advantage.

Canine oral fibrosarcomas: a retrospective analysis of 65 cases (1998-2010)

The objective of this retrospective study was to report the outcome of treatment of canine oral fibrosarcomas (FSA) in relation to median survival and progression-free survival (PFS), and to report whether grade was prognostic in relation to median survival. Sixty-five dogs with oral FSA presented to the WSU VTH between June 1998 and March 2010. Significant predictors of median survival were location (P = 0.0099), tumour size or oral stage (P = 0.0312), type of surgery (P = 0.0182), margins (P = 0.0329) and grade (P = 0.0251). Significant predictors of PFS were location (P = 0.0177), and radiation protocol (P = 0.0343). A combination of surgery and radiation was the strongest predictor of prolonged median survival (P = 0.0183) and PFS (P = 0.0263) at 505 and 301 days, respectively. Treatment of canine oral FSA with a combination of surgery and radiation therapy provided the longest median survivals.

Response rate and duration associated with a 4Gy 5 fraction palliative radiation protocol

The purpose of this retrospective study was to determine if 4Gy fractions over 5 consecutive days is an effective and safe palliative radiation protocol for dogs and cats. Eighty patients (22 cats, 58 dogs) with complete follow-up information were evaluated. Overall response rate (ORR) for all patients was 67%. Median progression free survival (MPFS) was 3.3 months and median survival (MST) was 4.2 months. Primary bone tumors were the most common tumors treated. The ORR for primary bone tumors was 66.6%, the MPFS was 3.5 months, and MST was 3 months. The most common tumor treated in cats was oral squamous cell carcinoma and ORR was 54.5 %, the MPFS was 1.8 months, and MST was 3 months. Soft tissue sarcomas were the second most common tumor treated in dogs (10). ORR was 80% and the two other patients had stable disease. MPFS was 5.7 months and MST was 7.9 months. Overall rate of toxicity was 18.4% in 65 sites that were evaluated for toxicity. Acute toxicities were all grade I or II and occurred in 16.9 % of patients evaluated. All late toxicity was grade I alopecia and leukotrichia. There appears to be a comparable response rate for this palliative protocol as compared to others historically. This response was seen over a wide range of tumors. We also documented a low toxicity profile in a shorter overall treatment time, making this protocol more attractive for some clients.

Radiotherapy-induced myelosuppression in dogs: 103 cases (2002-2006)

Definitive radiotherapy refers to delivery of large doses, typically 48-62 Gray, of ionizing radiation over several weeks using a daily or alternate-day fractionation schedule. The impact of definitive radiotherapy alone on haematopoiesis in tumour-bearing dogs is unknown. Medical records from 103 dogs receiving definitive (60) Cobalt teletherapy for cancer over a 5-year period were reviewed for signalment, tumour type and location, total radiotherapy dose and fractionation scheme. Complete blood count data were collected before, halfway through, and at the end of radiation treatment, and analysed for changes associated with patient variables. The results demonstrate significant reductions in haematocrit, total white blood cell count, neutrophils, eosinophils, monocytes, lymphocytes and platelets occurred during definitive radiotherapy but remained within laboratory reference intervals. These data are important for anticipation of toxicity associated with combinations of radiotherapy and chemotherapy in dogs but do not support the routine monitoring of haematology parameters during definitive radiotherapy.

Radiation therapy for palliation of sarcoma metastases: a unique and uniform hypofractionation experience

Radiotherapy (RT) is our preferred modality for local palliation of metastatic soft tissue sarcoma (STS). A short and intense course of RT is usually needed for rapid palliation and local control of metastatic disease. Seventeen patients at a median age of 61 had symptomatic metastatic sarcoma and required rapid palliation. The symptoms related to the metastases were either pain or discomfort. All patients were treated by a short and intensive course of administration: 39 Gy were given in 13 fractions of 3 Gy/day, 5 times a week. Median follow-up period was 25 weeks. The treatment was well tolerated. Acute side effects included grade one skin toxicity. No wound complications were noted among those undergoing surgery. Late side effects included skin pigmentation and induration of irradiated soft tissues. Durable pain control was achieved in 12 out 15 cases treated for gross metastases. Tumor progression was seen in the 3 other cases within a period of two to nine months. Among 5 lesions which were irradiated as an adjunctive treatment following resection, no local recurrence was observed. The results of this series, although limited in size, point to the safety and feasibility of hypofractionated RT for palliation of musculoskeletal metastases from sarcoma.