The Irish Wolfhound Foundation

Fosamax Revisited

Posted Dec 06, 2012.

Twelve years ago a report of two beagle dogs with osteosarcoma and tumor regression after treatment with alendronate (fosamax) was published in the veterinary literature.  Because so many Irish Wolfhounds die of osteosarcoma this treatment was investigated in Irish Wolfhounds with a study headed by Dr. Bill Dernell, then at Colorado State University. 30 dogs were enrolled in the study and several others were treated off protocol. Unfortunately follow-up was very poor. Too few owners took their hounds for the formal followup visits and the study results could not be published without objective information. However informal follow-up reports were provided by owners in order to receive the drug. There was some response with improved mobility and less pain in most of the dogs which unfortunately did not last longer than 1-3 months. There were 4 dogs with very good responses including regression of the tumor. Two of these dogs survived to die from other causes.

There has been prolific and conflicting data from studies with bisphosphonates used to treat malignancy and bone metastasis in human cancer. Intravenous bisphosphonates are widely used to prevent and treat bone metastases in kidney, breast, prostate, bone cancer with some success.

Dr.Tim Fan of the University of Illinois investigated the use of intravenous bisphosphonates combined with radiation therapy for canine osteosarcoma. There has been some success with this therapy and it is now widely utilized, although expensive. Dr. Fan was concerned about the absorption of fosamax which was not well documented in canines. There was also little information on toxicity including GI problems or ulcers of the esophagus which might be caused by taking the drug orally.

Side Effects from Oral Fosamax in Irish Wolfhounds

There are anecdotal reports of tolerance to oral fosamax on over 50 Irish Wolfhounds. Two dogs developed diarrhea and stopped the drug. There was no vomiting reported. There was no gastrointestinal bleeding or decreased appetite reported. In humans long term fosamax therapy at high doses can result in kidney dysfunction, GI upset, jaw necrosis after dental work and some reported cases of femur fractures. No reports of any of these problems are known in Irish Wolfhounds. These are rare but real. Because osteosarcoma is a rapidly progressive and fatal disease in our hounds blood work has usually not been done on dogs taking fosamax. In the dogs in the original study who did have labs done there were no abnormalities in renal function, liver function or electrolytes.

Maybe the Dose Was Wrong?

During the original IW study with fosamax one of the study participants also had a Saluki who developed osteosarcoma. The Saluki (weight about 50 lbs) was treated with the same dose used for her wolfhound. The Saluki responded with tumor regression and lived 6 years afterwards. Treatment was stopped after a year without recurrence.

Many years passed. Fosamax is on the market in generic form and quite inexpensive. A DVM had a wolfhound with right radial osteosarcoma and called. We discussed trying a much higher dose than used previously in the study remembering the saluki. She tried a much higher dose with very good response including tumor regression and improvement in pain for the next 3 months. This increased dose was tried on three other dogs with the same improvement.

Personal Story

My beautiful bitch developed a limp after galloping on Sept 13th 2011. Radiographs showed an osteolytic lesion right radius. She was unable to get in and out of the car, jump on the couch or trot without pain despite Rimadyl and tramadol (which she did poorly on). She was started on the new dose fosamax protocol and within 3 weeks was symptom free. She was off all meds except the fosamax for 7 months before the tumor gradually began to enlarge. Fosamax had been stopped the 3 weeks before the tumor began to grow. Response to restarting the fosamax has been poor with slow tumor growth and symptoms. But she has lived a year fully active with no problems.  Despite taking massive doses (for a human) she had no side effects at all.

Please remember that this was a protocol of desperation. It offers some hope for improved symptoms for at least some time. There have been no harmful side effects although it has been used on only a small number of dogs. It can be used for dogs who do not like to leave home for treatment, when treatment with more aggressive means is not desired or available. It is inexpensive and offers more than just treatment for pain. Because of the way bisphosphonates work (osteoclast or bone destroyer cell inhibition) they may be more helpful if the x-ray shows an osteolytic picture - or, some tumors will respond better than others depending on their make-up.

 

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