New survival times and treatments for anal sac cancer in dogs

Abstract

Apocrine gland anal sac adenocarcinoma (AGASACA) is a locally invasive tumor with a high potential for early metastasis. The most recent studies indicate that 23.4–83% of dogs have metastases to the iliosacral lymph nodes (LNs), and 2.1–31% have distant metastases to other organs at the time of first presentation. Usually, only one anal sac is affected, but bilateral involvement has been reported in 4–20% of dogs. About 16–53% of dogs present with paraneoplastic hypercalcemia. The most recent studies show an overall improvement in median survival time (MST) (15–28 months) for dogs with different stages of AGASACA treated with surgery and adjuvant therapy compared to those treated with chemotherapy alone (6.9 to 8.7 months). The highest MST (22–32 months) was reported when radiation therapy (RT) was selected as a sole or adjunctive treatment. Several studies have been published to identify the subset of tumors with more aggressive behavior and higher metastatic potential. The main negative prognostic factors are the size of the primary tumor, metastatic regional lymphadenopathy at first presentation, the size and the number of the metastatic lymph nodes, distant metastases at the time of diagnosis, and the histological characteristics of the primary tumor. In this critical review, the latest advancements in histological diagnosis, staging, treatment, and prognosis of AGASACA are described. The aim is to provide a full overview of this neoplasm, focusing on the latest advancements on prognostic variables and treatments.