Radiation Therapy Treatments

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According to Dr. Knapp at Purdue University, “radiation therapy has been used to successfully control TCC growth in the bladder in dogs. In early radiation studies, the side effects were serious and included a scarred, shrunken bladder, and irritation to surrounding organs. One of the challenges in applying radiation to the bladder is that the bladder can move or flop within the abdomen and take on a different shape depending on how much urine is in the bladder and if structures next to the bladder such as the bowel are pushing in on the bladder. With better imaging, radiation therapy of the bladder has become much safer than in years past.  The optimal treatment protocols (doses, frequency) and the level of benefit offered by radiation therapy require further study” (1).

North Carolina State Veterinary Hospital has advanced radiation technology to treat TCC. Their web site from their Veterinary Radiation Oncology Department has good information along with a summary about using radiation as a treatment option for TCC (2).

Radiation studies using IM/IGRT have the longest survival rates for TCC than any other studied treatment at 654 days (3).

IM/IGRT

Newer radiation technology has provided better imaging with 3D imaging using CT scans to provide for intensity modulated radiotherapy. This allows better targeting of the tumor than what has been done historically. A study was conducted in 2012, using intensity‐modulated and image‐guided radiation therapy (IM/IGRT) for treatment of genitourinary carcinomas (CGUC) in 21 dogs. Total radiation dose ranged from 54–58 Gy, delivered in 20 daily fractions over 4 weeks. The median progression free interval was 317 days and the median survival time was 654 days (3). IM/IGRT has the longest studied median survival time of any treatment option on this site. According to North Carolina State University Veterinary Hospital, “IM/IGRT in combination with NSAIDs and chemotherapy is currently considered the best possible treatment in most cases of bladder and prostate cancer (2)”.

Grade 1 and 2 acute gastrointestinal toxicity developed in 33% and 5% of dogs, respectively. Grade 1 and 2 acute genitourinary and grade 1 acute integumentary toxicity were documented in 5%, 5%, and 20% of dogs, respectively. 4/21(19%) dogs experienced late grade 3 gastrointestinal or genitourinary toxicity. Each presented 6–18 months after completion of IM/IGRT, and were successfully palliated with either stenting or surgery. 60% of dog owners noted subjective improvement in quality of life and 30% remained unchanged (3).

Here is Colorado State University’s information on using IMRT for Bladder Cancer.

Palliative Radiation (pRT)

Palliative intent Radiation offers the ability to reduce symptoms of TCC, offer some tumor control and help your pet feel better. A study conducted in 2016, used 10 daily (M-F) fractions of 2.7 Gy. 6 dogs used this treatment as first line therapy and 7 dogs used this as a rescue therapy after trying chemotherapy. 62% of dogs studied experienced complete remission or partial remission and the remaining 38% had stable disease as measured after 6 weeks of radiation. Median survival time was 150 days (range, 25 - 763). Acute side effects occurred in 31% of patients at a low grade 1 or 2. Late stage side effects were not found. Subjective clinical improvement was found in 77% of dogs (4).

Another study in 2004, combined Piroxicam (NSAID), Mitoxantrone (Chemotherapy) along with 6 weekly fractions of 5.75 Gy of Radiotherapy for 10 dogs with only minimal side effects. “Only two (22%) dogs achieved a measurable partial response; however, 90% of the dogs had amelioration of their urinary clinical signs. The median survival time for all dogs was 326 days” (5).

Stereotactictic Radiation Therapy (SRT)

In general, Stereotactic Radiation Therapy is not recommended for treating TCC due to the risks of harming other organs. According to North Carolina State University Veterinary Hospital, “also commonly referred to as SRS (stereotactic radiosurgery), GammaKnife® or CyberKnife® treatment is the newest and most convenient treatment available for cancers of the urinary tract. Unfortunately, SRT is not appropriate for many dogs with cancers of the bladder, urethra and prostate. If you’re interested, be sure to ask your radiation oncologist whether they think SRT could be a safe and effective option for your pet” (2). No studies have been conducted using SRT to treat TCC.

Supposedly, PetCure Oncology Group is working on publishing a study using SRT to treat TCC. They have this data on their website showing median survival time of 364 days (6). However, my veterinarian and I have contacted PetCure to get more information about this chart and they will not provide any additional information even though the chart states they will. There is no discussion on side effects.

HDR Brachytherapy

High Dose Rate (HDR) Brachytherapy is being used by Dr. Clayton Watkins in Utah to treat TCC. He works with a human Radiation Oncologist, Dr. John Hayes, that specializes in Brachytherapy to mimic human radiation treatments for pets. “Brachytherapy is the practice of treating cancer by placing a radioactive source directly into the cancer tissue. Multiple hollow catheters are placed within the tumor and a single radioactive source moves sequentially in and out of each catheter treating the tumor from the inside out. HDR brachytherapy allows the doctor to more precisely control the dose delivery within the tumor, and more accurately limit the dose to the surrounding normal tissue” (7). Dr. Watkins has a great video under "Lectures" explaining how he manages TCC of the bladder starting at about 1:05:00 using resection and Brachytherapy, and how he manages TCC in the urethra at 0:27:00, prostate at 0:39:00. Unfortunately, there are not any studies, but he is wonderful to talk to and discuss how he can help your pet. This document describes his cutting edge technology (8).

North Carolina State University Veterinary Hospital - Radiation Treatment Option Summary

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 References (includes links to source documents):

  1. Knapp, D., 2020. Urinary Bladder Cancer Research. [online] Purdue University College of Veterinary Medicine. Available at: <https://vet.purdue.edu/pcop/urinary-bladder-cancer-research.php#:~:text=The%20most%20common%20cancer%20of,cells%20that%20line%20the%20bladder.> [Accessed 16 September 2020].

  2. NC State Veterinary Medicine. 2020. NC State Veterinary Hospital: Radiation Bladder And Prostate Cancer - NC State Veterinary Medicine. [online] Available at: <https://cvm.ncsu.edu/nc-state-vet-hospital/small-animal/radiation-oncology/bladder-and-prostate-cancer/> [Accessed 18 September 2020].

  3. Nolan MW, Kogan L, Griffin LR, et al. Intensity-modulated and image-guided radiation therapy for treatment of genitourinary carcinomas in dogs. J Vet Intern Med. 2012;26(4):987-995. doi:10.1111/j.1939-1676.2012.00946.x

  4. Choy K, Fidel J. TOLERABILITY AND TUMOR RESPONSE OF A NOVEL LOW-DOSE PALLIATIVE RADIATION THERAPY PROTOCOL IN DOGS WITH TRANSITIONAL CELL CARCINOMA OF THE BLADDER AND URETHRA. Vet Radiol Ultrasound. 2016;57(3):341-351. doi:10.1111/vru.12339

  5. Poirier VJ, Forrest LJ, Adams WM, Vail DM. Piroxicam, mitoxantrone, and coarse fraction radiotherapy for the treatment of transitional cell carcinoma of the bladder in 10 dogs: a pilot study. J Am Anim Hosp Assoc. 2004;40(2):131-136. doi:10.5326/0400131

  6. Petcureoncology.com. 2019. [online] Available at: <https://petcureoncology.com/wp-content/uploads/Preliminary-Data-Presented-at-VCS-2019.pdf> [Accessed 18 September 2020].

  7. Vetmedutahclinic.com. 2020. [online] Available at: <https://www.vetmedutahclinic.com/> [Accessed 20 September 2020].

  8. Unknown, 2018. Utah Veterinarian And Human Radiation Oncologist Create World's First HDR Brachytherapy Center For Pets. [online] https://utahbusiness.com/category/press-releases/. Available at: <https://030fdac1-dcb4-48b2-a1e1-245f459aaf1a.filesusr.com/ugd/d706b4_cdcede210f264df1b2a54fe5959dcdac.pdf> [Accessed 23 November 2020].