Adenocarcinoma is the second most common gastrointestinal tumor in cats and the most common tumor found in the colon. Colonic adenocarcinoma is both locally invasive and frequently has advanced metastasis at the time of presentation. Aggressive local surgery (subtotal colectomy) improves survival time in cats, but patients eventually succumb to metastasis, warranting adjuvant treatment with chemotherapy. Carboplatin is an alkylating platinum-based chemotherapeutic agent and has been shown to have efficacy in humans and dogs with carcinomas. Limited previous studies have shown mild to moderate efficacy and safety of carboplatin in cats with carcinomas, meriting its investigation as an adjuvant therapy for colonic adenocarcinomas.
This retrospective study evaluated signalment, diagnostic findings, disease-free interval, survival time, chemotherapeutic toxicoses, and prognostic factors for 18 cats with colonic adenocarcinoma treated with subtotal colectomy and monthly carboplatin. Interestingly, cats initially presenting with weight loss had a longer median disease-free interval (290 days versus 75 days), suggesting that a more chronic disease course occurs when weight loss is present. Four cats without weight loss had distant metastasis and a more acute presentation. Median survival time for all cats was 269 days, with cats without distant metastasis surviving 340 days and cats with distant metastasis surviving 200 days. For comparison, in a previous study, cats treated with subtotal colectomy alone lived only 56 days. Carboplatin toxicities reported included low-grade neutropenia, thrombocytopenia, and gastrointestinal toxicity, none of which required reduction or delay in treatment. One cat developed azotemia and carboplatin treatment was stopped after the fifth monthly dose. In conclusion, cats with colonic adenocarcinoma commonly present with colonic obstruction and usually remain patent after subtotal colectomy, but in the end, they are often euthanized due to metastasis, warranting early adjuvant chemotherapy. In this study, carboplatin was shown to have minimal toxicity and to be a viable adjunct for treating this disease. [GO]
See also: Green ML, Smith JD and Kass PH. Surgical versus non-surgical treatment of feline small intestinal adenocarcinoma and the influence of metastasis on long-term survival in 18 cats (2000-2007). Can Vet J. 2011; 52: 1101-5. [Free, full text article]