Successful treatment of an equine preputial fibrosarcoma using 5-fluorouracil/evaluation of the treatment using quantitative PCNA and Ki67 (MIB 1) immunostaining. (case report).

The study involves an 18-month-old pony diagnosed with a fibrosarcoma, a type of cancer, in the prepuce area. The pony was successfully treated using topical 5-fluorouracil over two months, and biopsies were taken before and after treatment to monitor the success of therapy. Post-treatment, these samples displayed a significant reduction in measures related to cancer growth, although still higher than healthy control values, probably due to an inflammatory response to the medication. The pony made a full recovery, and the results imply that such a treatment could be considered for similar cases in horses in future.

Treatment and Monitoring

• The study reported on the treatment of a young pony that had severe fibrosarcoma, a type of cancer, affecting the prepuce.
• The treatment involved the topical application of chemotherapy drug 5-fluorouracil. This treatment continued over two months.
• To monitor the progression of the disease and the effectiveness of the treatment, biopsies were taken both before and after the treatment period. Additionally, a biopsy from a healthy horse was taken as a control for comparison.

Assessing Treatment Effectiveness

• The biopsied tissue was immunochemically stained to highlight Proliferating Cell Nuclear Antigen (PCNA) and Ki67 (MIB1) – two markers of cell proliferation that can indicate cancer growth.
• Computerized quantitative image analysis was used to calculate the Mitotic Index (indicative of cell division rate), Growth Fraction (reflecting proportion of proliferating cells), and the total nuclear area percentage of the dermis.
• This detailed analysis showed a significant decrease in all these factors at the end of the treatment period as compared to the initial biopsy tissue, indicating the treatment significantly reduced the fast-growing cancer cells.
• Despite this success, these values remained higher than those of healthy tissue, which the authors suggest could be due to an inflammation caused by the cytostatic drug.

Outcomes and Implications

• The pony showed a full recovery after the treatment with no visible prepuce lesions.
• A follow-up six months post-treatment showed no signs of a recurrence of the cancer.
• The success of the treatment in this case could encourage further clinical trials for the treatment of similar malignant skin tumours in horses.
• Last but importantly, the study demonstrates how quantitative analysis of cell proliferation in biopsies can be used effectively to evaluate and follow up treatment responses in equine cancer cases.