Despite the availability of commercial tissue equivalent bolus material, wet gauze has an application in radiation therapy to provide superior conformance to irregular contours. Wet gauze bolus has the potential to reduce air gaps between the bolus and surface, which could decrease surface dose if sufficiently large to disrupt electronic equilibrium. Wet gauze bolus is often fabricated and wetness judged qualitatively. We assessed the effect of specific gauze wetness levels, quantified in terms of physical density, at various field sizes with respect to their effectiveness as bolus material compared with Superflab^®. For large fields, >7 × 7 cm² in this study, wet gauze sponges with a physical density of 1.02 g/cm³ performed essentially identical to Superflab^®; at a smaller field size the wet gauze was slightly less effective, likely due to the heterogeneity of the gauze‐water matrix. Gauze that was wetter, with a physical density of 1.2 g/cm³, or less wet, with a physical density of 0.75 g/cm³ was not as effective either due to enhanced photon absorption in the wetter sponges, or less effective establishment of electronic equilibrium in the less wet sponges. The presence of an air gap under Superflab^® led to reduced surface dose, especially for small fields and large air gaps. Thus, if Superflab^® use leads to poor contact with the skin, wet gauze having a physical density of 1.02 g/cm³ can be used as a substitute. Judging the water content of wet gauze subjectively is not acceptable as over‐ or under wetness can lead to decreased effectiveness of the bolus material.

Accelerated radiation therapy protocols address the specific biology of aggressive oropharyngeal squamous cell carcinoma and this approach was applied in 5 feline and 3 canine oropharyngeal squamous cell carcinoma patients where surgery was not possible (4/5 feline and 2/3 canine cases) or was declined (1/5 feline and 1/3 canine cases). A protocol using 14 fractions of 3.5 Gy over 9-days, combined with carboplatin chemotherapy as a radiosensitiser (total dose 180 mg/m²in feline and 300 mg/m²in canine cases) resulted in a complete tumor response in most cases (4/5 feline and 3/3 canine cases) with acceptable acute and long-term side effects. Results achieved in feline cases correspond with published data where these specific radiotherapy protocols were employed. A complete response and long-term survival (> 2-years) was achieved in all canine patients. Although no standardized chemoradiotherapy protocols currently exist, this therapeutic approach can be a useful addition for the management of oropharyngeal squamous cell carcinoma of cats and dogs when the goals of treatment include maximizing tumor control while maintaining function and quality of life.

Introduction: Standard care for malignant tumors arising next to a bone structure is surgical removal with safety margins, followed by external beam radiotherapy (EBRT). Complete tumor removal can result in large bone defects. A two-step bone reconstruction technique using the induced membrane (IM) technique has proven its efficacy to bridge gap nonunion. During the first step, a spacer is placed in the bone gap. The spacer then is removed and the IM around it is filled with autologous cancellous bone graft. However, the feasibility of this technique with the addition of adjuvant EBRT between the two reconstruction steps has not yet been studied. Polymethyl methacrylate (PMMA) used to be the standard spacer material for the first step. Silicone spacers could replace them owing to their good behavior when submitted to EBRT and their easier removal from the surgical site during the second step. The aim of this study was to evaluate the influence of EBRT on the histological and biochemical properties of IM induced using PMMA or silicone as spacer. Materials and Methods: The analyses were performed on PMMA- or silicone-IM with and without EBRT in a 6-mm bilateral femoral defect in 32 rats. Thickness and vessel content were measured in both groups. Bone morphogenetic protein 2 (BMP2) and vascular endothelial growth factor (VEGF) content in lysates of the crushed membranes were measured by enzyme immunoassay. Finally, alkaline phosphatase activity was analyzed in human bone marrow stromal cell cultures in contact with the same lysates. Results: EBRT did not change the histological structure of the cellular internal layer or the fibrous outer layer. The nature of the spacer only influenced IM thickness, PMMA-IM with external radiotherapy being significantly thicker. EBRT decreased the vascular density of IM but was less effective on VEGF/BMP2 production. In vitro, IM could have an osteoinductive potential on human bone marrow stem cells. Conclusion: EBRT did not modify the histological properties of IMs but decreased their vascular density. VEGF and BMP2 production within IMs was not affected by EBRT. Silicone spacers are able to induce membranes with similar histological characteristics to PMMA-IM.

CASE DESCRIPTION A 4-year-old sexually intact male leucistic axolotl (Ambystoma mexicanum) was presented with a 2-week history of dysrexia and difficulty swallowing. CLINICAL FINDINGS Physical examination revealed a 1-cm-diameter intraoral mass on the rostral aspect of the palate and swelling of the left nasal fossa. Local invasion into the left nasal fossa was suspected during oral examination. The lesion was marginally excised, and an incompletely excised olfactory neuroblastoma was diagnosed histologically. Five weeks later, physical examination revealed persistent erythema, delayed healing of the rostral portion of the palate, and a mild facial deformity associated with a white mass in the nasal cavity. TREATMENT AND OUTCOME 6 weeks after excision, adjuvant electron (6-MeV) beam radiotherapy was initiated for treatment of the incompletely excised olfactory neuroblastoma and likely presence of a recurrent mass. The protocol consisted of 4 weekly fractions of 8 Gy each (total, 32 Gy) with the axolotl under anesthesia. No acute adverse radiation effects were noted following radiotherapy. The oral erythema resolved after the third session. No recurrence was observed 2 months after treatment, and the owners reported no abnormal signs at home. The axolotl died 3.5 months after radiotherapy was completed (8 months after marginal excision of the tumor) secondary to an environmental management failure. Postmortem histologic evaluation showed no evidence of neoplasia. CLINICAL RELEVANCE In axolotls, olfactory neuroblastoma should be considered in the differential diagnosis of intraoral palatal masses. This report describes the first application of radiotherapy for treatment of an olfactory neuroblastoma in an axolotl.