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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com elemenTs oF oncology Peer reviewed 56 Nasal Tumors: Advanced Techniques Lead to Fewer Side Effects Recent advances in cancer treatment delivery have diminished clinically signifcant acute treatment side effects—effects commonly associated with signifcant morbidity in dogs and cats—for nasal tumors. 31 Intensity-modulated radiation therapy (IMRT), an advanced treatment delivery system, shapes the radiation beam to nearly any complex shape (figure 6). The highly conformed shape of the beam allows for sharp "falloff" at the borders of the dose, resulting in diminished occurrence or elimination of side effects, which is possible because the energy from the radiation treatment beam is focused on the tumor, avoiding organs with sensitive pain receptors, such as the skin and oral mucosa. This advanced therapeutic modality is particularly important in treatment of nasal tumors, which are adjacent to critical structures, such as the eyes and brain, and limits common side effects, such as mucositis, moist desquamation, and keratoconjunctivitis sicca (figure 7). N a Figure 7. Patient with nasal tumor one week after defnitive radiation therapy (19 fractions) using 3-dimensional conformal radiation therapy plan; note the extensive area of radiating moist desquamation present on the medial canthus and lips and areas of redness and dry desquamation present on the dorsum of the nose and caudal to the eye over the frontal sinuses (A). Patient with nasal tumor one week after defnitive radiation therapy using advanced, highly conformal, IMRT plan (19 fractions). Although signifcant moist desquamation is present, it is limited to a smaller area, radiating rostrally from the medial canthus (B). The patient in B only required NSAID pain medication during treatment, whereas the patient in A required multiple medications to manage painful side effects. Figure 6. Axial-slice computed tomography scans of the nasal cavity in 2 dogs receiving defnitive radiation therapy for a nasal tumor. Red and yellow areas are receiving 100% of the prescribed dose; blue and green areas are receiving 50% of the prescribed dose. Three- dimensional conformal radiation therapy plan (A); IMRT plan (B). Note that the volume of normal tissue, such as the mandible and skin, receive a signifcantly reduced dose. * = tumor; + = tongue; # = lips A B A B