Thymoma chemotherapy

Re: Thymoma chemotherapy

Gerry Polton — Thu, 04 Dec 2014 08:34:49 GMT

Hi Kara

I would prefer prednisolone if I had to choose one. The only reason for preferring L-asparaginase that I can think of right now would be if prednisolone were contraindicated for some reason, for example concurrent NSAID administration. In favour of steroids, they could be given for months whereas we typically only give L-asparaginase a few times (that's a story for another day). The side effects of steroids are familiar to every practising vet who has been out of school for a week or more. Finally steroids are a darn sight cheaper than L-asparaginase. There may be a perception that L-asparaginase would work quicker but steroids can also achieve a really brisk improvement, if there is going to be one at all.

Hope that helps

Gerry

Re: Thymoma chemotherapy

Kara Gibson — Tue, 02 Dec 2014 09:31:55 GMT

Gerry,

Would you have any preference for using L-asparaginase over prednisolone given the potential side effects? If so what dosing regime would you use?

Thanks in advance,

Kara

Re: Thymoma chemotherapy

Kara Gibson — Fri, 18 Jul 2014 02:37:41 GMT

Thaks again Gerry, have passed on your advice to my colleague.

Re: Thymoma chemotherapy

Gerry Polton — Wed, 16 Jul 2014 08:47:59 GMT

Hi Kara

We don't really terat many thymoma cases with medical therapy. The reason for this though is that they do so well so much of the time with surgery. However, if surgery is not appropriate, and I can understand why that would be the case given the dog's age, you and your colleague will be pleased to learn that one of the most useful medical treatments in thymoma is prednisolone! In any thymoma a substantial proportion of the overall volume of the mass is comprised of normal lymphocytes. These normal lymphocytes are, to a greater or lesser degree, responsive to the administration of steroids. Removal of a proportion of these lymphocytes reduces the total volume of the mass and therefore reduces the effects of having a large intrathoracic mass. A bit like lymphoma, the duration of any benefit can be relatively short-lived, but it is most certainly worth a try.

Other non-surgical therapies include radiation therapy, which has been described in a case series in the veterinary literature and which achieved a median life expectancy of approximately eight months in dogs who were considered to be poor candidates for surgery. This would be expensive compared to prednisolone, of course. another option that is spoken about in hushed voices but makes some sort of biological sense is L-asparaginase, for the same reason that prednisolone would be effective, in that it is lymphocytolytic. However, like prednisolone, it is going to have a relatively short-lived effect.

A final thought: please be confident that this is thymoma. I gather that the cytology is suggestive rather than probative. If this were a thymoma, in a dog of this age with clinical signs related to the presence of a mass (I have assumed that's the case from your description) this should be a huge mass. If the mass is cranial to the heart but smaller than the heart, there is a reasonable chance that this is actually lymphoma, despite the indications to the contrary. Of course, if this were a case of lymphoma, while prednisolone or L-asparaginase or radiotherapy might all work quite well, a multidrug chemotherapy protocol would be expected to work better. It is notoriously difficult sometimes for lymphoma and thymoma to be discriminated on cytology alone (on histology too occasionally). My enthusiasm for pursuing a more definitive diagnosis is heavily influenced by my perception of how well the presenting complaint fits with my expectation for the diagnosis that has been proposed.

Gerry

Re: Thymoma chemotherapy

Tim Charlesworth — Tue, 15 Jul 2014 11:31:32 GMT

I am not the person to comment about chemo (will leave that to Gerry) but its worth considering laryngeal paralysis as a diagnosis in a dog of that signalement who is panting/mild cough. Could be in association with the mediastinal mass or part of the "GOLP" - geriatric onset labrador polyneuropathy that is now regarded as very common in the breed. Not answering your question I know but thought it may help!

Tim