Lomustine – A very useful drug for your oncology arsenal?
Lomustine in veterinary oncology is a valuable treatment option for several tumour types in cats and dogs. In this episode, we speak with Dr Jenny Helm to understand how lomustine fits into modern oncology protocols, including when to use it, how to monitor for side effects, and how to support owners through treatment.
By Dr. Darren Kelly MVB, DipECVIM-CA, MRCVS and Dr. Jenny Helm BVMS, CertSAM, DipECVIM-CA, FHEA, MRCVS
Overview
Darren Kelly and Jenny Helm discuss lomustine and the types of cases where it can be useful, during this episode. Jenny also considers the owner’s situation and discussions that the vet needs to have with the owner when planning the treatment options for different types of tumours. Side effects, different species, and pros and cons of lomustine use are considered.
Key Points Discussed in This Episode:
- When to Use Lomustine in Veterinary Oncology
- Common Cancers Treated with Lomustine
- Side Effects of Lomustine in Dogs and Cats
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Transcripts
Lomustine – A very useful drug for your oncology arsenal?
Host:
Welcome to the Bova UK Podcast, where we discuss diseases from diagnosis through to management. These podcasts are for registered vets and veterinary nurses. If you’re listening as a pet owner, please consult with your local veterinary surgeon for specific advice.
Today, I’m joined by Dr. Jenny Helm. Jenny completed her RCVS Certificate in Small Animal Medicine in 2008 and became a Diplomate of the European College of Veterinary Internal Medicine in 2012. She worked as an oncology clinician at the University of Glasgow before moving to a private referral centre as a senior oncology clinician. She enjoys all aspects of oncology, especially haematology and improving quality of life.
Today, we’re going to talk about lomustine, and how useful it is as part of the veterinary oncology arsenal.
Dr. Darren Kelly:
Hi Jenny, nice to speak with you this evening. I’m really looking forward to chatting about lomustine and getting your perspective on how you use it in practice.
Dr. Jenny Helm:
Hi Darren, thanks! I agree—lomustine is a fantastic chemotherapy drug. It’s an oral cytotoxic agent classified as an alkylating agent. It affects DNA, RNA, and protein synthesis. Though its exact mechanism isn’t fully understood, it’s not cell cycle specific, which is important to note.
Dr. Darren Kelly:
Which types of cancer do you typically treat with lomustine?
Dr. Jenny Helm:
A wide range, actually. I use it for lymphoma—especially T-cell lymphomas—and for specific sarcomas and carcinomas. It’s also useful in rescue protocols when first-line treatments fail. For T-cell epitheliotropic lymphoma, I often use lomustine as a first-line treatment. I’ve also recently started using it in feline rescue protocols.
Dr. Darren Kelly:
Would you say we should be immunophenotyping all lymphoma cases?
Dr. Jenny Helm:
Yes, where possible. It helps guide treatment decisions. Cost or the owner’s willingness may be barriers, but in most cases, it’s very beneficial.
Dr. Darren Kelly:
Do you offer single-agent protocols?
Dr. Jenny Helm:
Absolutely. Not all owners can commit to intensive weekly treatments. Lomustine’s oral form and three-week interval make it ideal for a more hands-off approach.
Dr. Darren Kelly:
What about its use in other tumours like histiocytic sarcomas?
Dr. Jenny Helm:
Yes, I use it for periarticular histiocytic sarcomas, often post-surgery or with radiotherapy. I’ve also tried it in disseminated forms to extend quality of life.
Dr. Darren Kelly:
How about mast cell tumours?
Dr. Jenny Helm:
Not usually my first choice—I prefer vinblastine and prednisone—but lomustine is an option, especially if logistics make weekly visits difficult. In high-grade or refractory cases, I’ve used it with some success.
Dr. Darren Kelly:
What’s your dosing protocol?
Dr. Jenny Helm:
In dogs, I dose 50–70 mg/m², usually starting at 60. In cats, it’s lower due to prolonged myelosuppression. We monitor neutrophils at day 7 and adjust as needed. Dose escalation is possible if well tolerated. Liver toxicity is a concern, so we also monitor ALT and ALP closely. I use SAMe and milk thistle for liver support.
Dr. Darren Kelly:
Do you only use Denamarin?
Dr. Jenny Helm:
Not necessarily. As long as the product contains the same active ingredients—SAMe and silybin—I think it’s reasonable. The original study used Denamarin, so I often stick with that.
Dr. Darren Kelly:
Any final points?
Dr. Jenny Helm:
Yes—keep an eye on platelet levels, as lomustine can cause thrombocytopenia. Blood smears help confirm if low counts are real. Monitoring is key. Lomustine is versatile, effective, and invaluable when used thoughtfully.
Dr. Darren Kelly:
Thanks, Jenny. This has been a really insightful discussion!
