Medical Management of Anal Sac SCCs

Cutaneous squamous cell carcinoma (SCC) typically occurs in the perineum, scrotum, nasal planum, and limbs. Only 5 anal sac SCCs have been previously reported; all were treated surgically. Cutaneous SCCs are less metastatic than adenocarcinomas; anal sac SCCs may act similarly, but long-term data are lacking.

This report details 3 cases of anal sac SCC managed medically. All were unilateral with no metastases found. Because of concerns about inability to achieve clean surgical margins and the strong potential for fecal incontinence, surgery was not pursued. Patients were given meloxicam (0.1 mg/kg PO q24h) as sole palliative treatment. Two of the dogs were euthanized because of tumor progression at 2.6 and 5 months; the third was lost to follow-up after 7 months. 

These survival statistics are comparable to previous cases treated surgically. Meloxicam was chosen for its antiinflammatory and anti-COX-2 properties, but precisely how it contributed to survival times remains unclear. As with cutaneous SCC, multimodal local control of anal sac SCC may be prudent for long-term survival and warrants further study. Such techniques include cryotherapy, radiotherapy, plesiotherapy, brachytherapy, chemotherapy, or photodynamic therapy.

Commentary

Anal sac tumors are important quality-of-life issues for our patients. Attention to analgesia and stool quality through the use of non-constipating drugs, diet, and alternative medicine may be important palliative considerations. Antiinflammatory drugs, including meloxicam, are important because they have anti-tumor effects and do not constipate. Additionally, substance P inhibitors, sodium channel blockers, and N-methyl-D-aspartate (NMDA) inhibitors may be useful for clinical signs associated with a caudal abdominal mass effect. In-patient care could include epidural opiate administration for severe end-stage patients.—Heather Troyer, DVM, DABVP, CVA