Fibrosarcoma chemotherapy

Re: Fibrosarcoma chemotherapy

Gerry Polton — Tue, 17 Dec 2013 12:09:27 GMT

Hi Marie

With absolutely no prior experience of python pathology, the detail of this report reads like a low to intermediate grade tumour. I err more towards the low than the intermediate but I don’t think we should get too hung up on the distinction. Importantly, the fact that it does not read as a high grade mass means that this is a tumour with a very low risk of metastasis and a low chance of responding favourably to conventional chemotherapy or indeed to radiotherapy. I think that really leaves you with the metronomic chemotherapy option, benign neglect or surgery if that has not been totally ruled out already. I cannot comment on the pharmacology of cyclophosphamide in reptiles. I presume you could just keep her warm and she would metabolise the drug perfectly (see how easy my life is compared to yours that I could possibly believe this).

I would be interested to know how you get on.

Best wishes

Gerry

Re: Fibrosarcoma chemotherapy

Marie Kubiak — Tue, 17 Dec 2013 10:56:48 GMT

I seem to have had a flurry of malignant neoplasms lately - all interesting but not good news for the patients!

I'll send you over the report, thanks for this.

I was hesitant to take wide margins into bone previously as the clinical appearance was not significantly different to the more common presentation of proliferative bacterial stomatitis and the snake maxilla is a much smaller and less well supported bone. It may be an option but I remain a little concerned about what I'd do to overall skull stability removing a significant section of maxilla, I think CT to get a better idea of extent into bone would be resisted too on cost grounds so excision wouldn't be properly targeted either.

Cyclosphosphamide and NSAIDs definitely sounds interesting and possible. I'll see what you think on the report first though,

thanks again,

Marie

Re: Fibrosarcoma chemotherapy

Gerry Polton — Tue, 17 Dec 2013 10:42:35 GMT

Wow, Marie! You see some amazing things. I absolutely cannot comment on chemo in reptiles. I can speak about management of these tumours in cats and dogs. Most of these tumours are relatively low grade, if we do not specify particular locations. The grade of the tumour can be determined by evaluation of the terms used in the histology report. Please feel free to send the report over for me to comment on further (gpolton@ndsr.co.uk) . For what it is worth, with a low or intermediate grade fibrosarcomas we would usually perform wide excision to include segmental maxillectomy with the aim of achieving a complete cure. These tumours are consistently unlikely to metastasise and the problem with them is one of local recurrence. Segmental maxillectomy is a routine procedure in dogs in our hands. However, with cats it is unusual in the extreme. This is partly due to the fact that the oral tumours of these two species are so different and partly due to the fact that cats simply do not enjoy the luxury of capacious cheeks and jowls like many dogs do, so we don't have the same range of options for reconstruction. I don't know enough about reptiles to know whether this is a stupid question, but is the reason that segmental maxillectomy is not being considered due to the fact that this would be a known impossibility? I do not imagine there would be functional impairment subsequently, so long as a simple repair could be achieved.

Chemotherapy is rarely indicated in fibrosarcomas. Most of the evidence in domestic patients (and humans) indicates an absence of evidence of efficacy. I have just had a paper accepted in which we believe we demonstrated chemotherapy efficacy in cats with high-grade (injection site) sarcomas. This reflects the human experience which is that only the high-grade tumours actually benefit from conventional chemotherapy. The reason for the italics is that fact that there is a growing acceptance of a novel approach to chemotherapy called metronomic or low-dose chemotherapy. This involves the concurrent adminsitratino of a low dose of a cytotoxic agent, classically cyclophosphamide, with a non-steroidal anti-inflammatory agent on a regular, once daily basis. There is a growing body of evidence that this treatment achieves benefits through cytotoxic actions against endothelial cell precursors and therefore against the growing tumour's ability to drive the development of a new blood supply, and through a positive immunological action whereby the treatment de-tolerises the immune system and enables it to recognise the tumour and to potentially eradicate it. The beauty of this approach in your patient would be the fact that medication is administered orally. I don't know whether daily administration would be feasible, or indeed appropriate.

Finally, fibrosarcomas are amenable to management by radiation therapy. The attraction of this approach is the fact that once treatment is complete, you can walk away rather than continuing a treatment course in the longer term. However, fibrosarcomas are not always radioresponsive and there would be a requirement for serial general anaesthetics to complete the treatment course.

A good starting point would be to send over the histology report.

Best of luck

Gerry