Dog Parvo Symptoms

Radiotherapy is a local cancer treatment modality and not meant to treat systemic disease. As previously mentioned, it is often combined with other adjuvant cancer treatment modalities, particularly chemotherapy and surgery. Covering every type of tumor is beyond the scope of this article. Below, is a table that generally illustrates which cases may benefit of radiotherapy, but each case should be addressed individually since exceptions do exist.

Cutaneous and soft tissue tumors of the trunk and extremities:

Mycosis fungoides (see Oral Tumors)

Cutaneous and soft tissue tumors of the trunk and extremities are best approached in most situations by aggressive surgical resection. However, complete resection is not always possible because of location. This is particularly difficult when distal limbs are involved and the amount of normal skin to close the incision becomes limited. Adjuvant radiation therapy is an effective approach to treat the residual tumor cells.

Mast cell tumors and Soft tissue sarcomas (fibrosarcoma, hemangiopericytoma, malignant fibrous histiocytoma, Neurofibrosarcoma, myxosarcoma, malignant giant cell tumors etc) are the most common tumor types treated with a combination of surgery and radiation. A cooperative study published in the proceedings of Veterinary Cancer Society reported disease-free intervals of 2 – 5 years in 88% of patients with mast cell tumors (MCT) treated with surgery and radiation. A 5-year survival rate of up to 86% was reported in a study of soft tissue sarcomas (STS) treated with surgery and radiation at the Animal Medical Center, New York.

The histological grade of MCT has a great impact on prognosis and should always be obtained before considering radiation. Because MCT will most commonly metastasize to the local lymph nodes and abdominal organs, and less commonly to the lungs, an abdominal ultrasound and radiograph is more critical than a thoracic radiograph for the staging work up. Local lymph nodes should also be evaluated for staging as they are often included in the treatment field.

A grading system has not been well established for Soft tissue sarcomas and is therefore not yet a routine part of the histopathology report of most laboratories. However, it is important to recognize that undifferentiated and fast growing STS have a significantly higher metastatic potential, and adjuvant chemotherapy should be strongly recommended with a significantly more guarded prognosis.

The Vaccine-induced Feline sarcomas are more aggressive tumors with a higher metastatic potential than sarcomas unrelated to vaccination, and need to be approached very aggressively. Presently, the best treatment is radiation therapy administered FIRST combined with chemotherapy, then followed by aggressive surgery.

Squamous cell carcinoma (SCC) on the trunk and extremities in canines is most commonly treated with surgical resection and generally has a good prognosis. The histopathologic characteristics should be thoroughly determined for prognostic purposes and chemotherapy is recommended for poorly differentiated tumors. For incompletely resected tumors, radiation therapy of residual disease is recommended.

Many other Cutaneous tumors (basal cell, plasma cell, etc…) have been effectively treated with radiation when incompletely resected. Only limited published data is available because of their infrequent numbers. This is because many such tumors are successfully treated with surgery alone. Like all other cases, these should be approached individually with a thorough diagnostic and staging work up before determining the most appropriate treatment.

Like most benign tumors, Infiltrative lipomas should be approached first with aggressive surgical resection (many lipomas will recur if the resection is incomplete – as it may be when they occur in limbs and infiltrate around critical structures like vessels, nerves and tendons). Recurring lipomas have been effectively treated with radiation therapy when complete resection is impossible due to extensive infiltration.