Chemotherapy protocol for feline mammary carcinoma

RE: Chemotherapy protocol for feline mammary carcinoma

Gerry Polton — Tue, 16 Feb 2016 17:53:42 GMT

Bob has hit the nail squarely on the head here. There is good evidence that chemotherapy extends survival. However, that evidence comes from oncologists and they are more experienced at deciding which cases are good candidates for chemotherapy and which are not and which fall into the grey area in the middle where they would be great candidates but they need a minor adjustment to the treatment plan.

Approximately 80% of feline mammary cancer patients die of metastatic disease. Chemotherapy and bilateral (and unilateral) mammary resection have been shown to extend life expectancy. The chemotherapy most widely used is doxorubicin but others used include epirubicin and mitoxantrone. The rubicins induce cumulative nephrotoxicity in cats, in the same way that we know they induce cumulative cardiotoxicity in dogs. One must be very careful in their assessment of a patient's likely excretory capacity before simply pressing on with a prescribed treatment dose. There are predictable consequences of administration of a near-toxic-to-otherwise-healthy-cats dose to a patient that is not able to metabolise or excrete the drug at a normal rate.

But for the record, I have just got off the 'phone to an owner who I have just advised not to pursue chemotherapy for her cat with a recently diagnosed mammary carcinoma. I don't know if my thought process is of interest but for those for whom it is: the mass was small and round (small size is a sort of positive indicator) and there were some not so bad histological characteristics of the tumour. These not so bad characteristics may mean that the tumour has a better than 20% chance of being non-metastatic but it is impossible to quantify that divergence from normal. What was also important in this case was an unshakeable sense that there was a smouldering renal problem. BUN and creatinine were both within normal limits though only just. However, there was evidence of cystolithiasis, dystrophic renal mineralisation and reported mild polydipsia. For me this case tipped too far on the do I, don't I balance: tumour not so bad, chemo metabolising capacity unknown but potentially not normal. Maybe this cat will die of metastasis in six months but at least it will not experience ill health because of something I chose to do.

Yours

Gerry

RE: Chemotherapy protocol for feline mammary carcinoma

Bob Russell — Tue, 16 Feb 2016 09:36:47 GMT

I have never found the benefits justify the downsides of treatment. Poor response, side effects and empty wallets!

Perhaps I have just selected the wrong patients!

RE: Chemotherapy protocol for feline mammary carcinoma

Martin Atkinson — Tue, 16 Feb 2016 09:29:48 GMT

[quote user="Thomas Johnson"]We stopped after the 3rd round of chemotherapy as she was becoming more unwell after each one.[/quote]That is the problem with Doxorubicin IME, I've had more than one client cease their pet's therapy because it makes them so unwell.

RE: Chemotherapy protocol for feline mammary carcinoma

Thomas Johnson — Tue, 16 Feb 2016 09:11:36 GMT

[quote user="Martin Atkinson"]

[quote user="Thomas Johnson"]The last one I treated with chemotherapy was 18 months ago, and Gerry Polton at NDSR recommended doxorubicin 25mg/m2, 5 treatments at 3 week intervals, with haematology checked before each treatment.[/quote]Did it work?

My take on this is that feline mammary carcinomas are poorly responsive to chemo so if there were no visible mets you wouldn't know in a year's time if it is still in remission whether it was because of or despite the treatment.

I would be interested on Gerry's take on whether it is really worth routine chemo in these cases.

[/quote]

We stopped after the 3rd round of chemotherapy as she was becoming more unwell after each one. She had no visible metastases, and had had a bilateral mammary strip so the chemotherapy was precautionary. 18 months later there is no evidence of recurrence.

RE: Chemotherapy protocol for feline mammary carcinoma

Martin Atkinson — Tue, 16 Feb 2016 09:07:51 GMT

I would be interested on Gerry's take on whether it is really worth routine chemo in these cases.

RE: Chemotherapy protocol for feline mammary carcinoma

Danny cazabon — Mon, 15 Feb 2016 17:06:22 GMT

Hello,

Left side regional mastectomy was performed.

That's excellent advice. Thank you both,

Danielle

RE: Chemotherapy protocol for feline mammary carcinoma

Gerry Polton — Mon, 15 Feb 2016 16:19:34 GMT

My thoughts exactly, Thomas!

Only other things to add:

1) Metastatic disease is reasonably prevalent at the time of diagnosis in these cases but not always evident on routine thoracic radiography. For example, it can also be found as plaques in the pleura or peritoneum. Optimal clinical staging would comprise thoracic and abdominal CT to enable visualisation of lesions at sites other than the pulmonary parenchyma. Of course, this is an expensive investigation and it is not appropriate to recommend a procedure which would then prevent the client affording the definitive treatment, if that were the case.

2) It is an accepted truth of feline mammary tumours that where there has been one, there is a high probability that there will be others. Therefore, many would recommend bilateral complete mammary resection. I can't tell from the terms used in your post what the extent of surgery performed for this patient was. It is possible that the bilateral strip has already been performed. This is another element of therapy though that merits discussion. If it's going to be done, I would advocate doing it before chemo rather than after and certainly not during.

Best wishes

Gerry

RE: Chemotherapy protocol for feline mammary carcinoma

Thomas Johnson — Mon, 15 Feb 2016 15:56:48 GMT

[quote user="Danielle Dillon"]

Hi,

Female neutered 8 yo. Mammary strip performed left 3-4 glands 1.5cm margin. However lymphatic invasion present. No signs of Mets to the chest. Abdomen flacced/ no enlarged mesenteric lns on ultrasound.

Any ideas about Chemo protocols for such an aggressive neoplasia?

[/quote]

The last one I treated with chemotherapy was 18 months ago, and Gerry Polton at NDSR recommended doxorubicin 25mg/m2, 5 treatments at 3 week intervals, with haematology checked before each treatment.