Definitive‐intent radiotherapy for sinonasal carcinoma in cats: A multicenter retrospective assessment

Abstract

Treatment of epithelial sinonasal tumours in cats is not commonly reported. In the newer reports, palliative radiation protocols have been described more often than definitive-intent protocols. In this multi-institutional retrospective study, we included 27 cats treated with single-modality radiotherapy. Cats were irradiated using 10 daily fractions of 4.2 Gy. Three cats (11.1%) experienced a complete clinical response and 17 (63%) had a partial clinical response. Stable clinical disease was noted in three cats (11.1%). Four cats (14.8%) showed progression within 3 months following treatment. The median time to progression for all cases was 269 days (95 % confidence intervals [CI]: 225; 314). The proportion of cats free of progression at 1 and 2 years was 24% (95% CI: 22%; 26%) and 5% (95% CI: 5%; 6%), respectively. None of the prognostic factors evaluated were predictive of outcome (anaemia, tumour volume at the time of staging, modified Adams stage, intracranial involvement, facial deformity, epistaxis, inappetence or weight loss). Median overall survival (OS) for all deaths was 452 days (95% CI: 334; 571). The proportion of cats alive at 1 and 2 years was 57% (95% CI: 37%; 77%) and 27% (95% CI: 25%; 29%), respectively. Surprisingly, cats with epistaxis had a longer median OS of 828 days (95% CI: 356; 1301) compared to 296 days (95% CI: 85; 508) in cats without epistaxis, (P = .04, Breslow). Radiation therapy used as a single modality for the treatment of feline sinonasal carcinoma improved clinical signs and was well tolerated but progression within a year was common.

Retrospective evaluation of intranasal carcinomas in cats treated with external‐beam radiotherapy: 42 cases

“…A median OST of 342 days in for 28 cats with nasal tumors that underwent coarse‐fractionated, PRT was also reported in another study 14 . Also, a study of 27 cats of INC treated with 10 daily (M‐F) fractions of 4.2 Gy reported median OST and PFS of 452 days and 269 days, respectively 8 . Although direct comparison between studies is challenging due to differences in protocols and cat populations, the present study further emphasizes that RT of any type could improve clinical signs and quality of life; we found that irrespective of treatment intent, most (>90%) irradiated cats had improvement in clinical signs.…”

“…4,5 Since complete excision cannot be achieved with surgery, and chemotherapy alone has minimal efficacy for the treatment of gross disease, 6,7 external beam radiotherapy (RT) is generally regarded as the treatment of choice for INC in cats; however, there is a paucity of published data describing clinical outcomes after treatment with modern irradiation protocols. 4,8 A 1989 publication describing use of orthovoltage RT for intranasal tumors in cats demonstrated that RT can provide long-term tumor control. 9 All cats with INC in that study (N = 3) received a total of 45 Gy in 10 fractions and lived more than 20 months (although 2 of them also underwent rhinotomy).…”

“…The primary goal of utilizing these technologies is to minimize dose to normal tissues while precisely delivering RT to target (ie, tumor) tissues. Cats with INC treated with 10 daily (Monday‐Friday) fractions of 4.2 Gy, and 89% of cats were treated with IMRT‐based treatment plans had median OST of 269 days while 11% treated with more traditional 3D conformal radiation therapy (3D‐CRT) methods had median OST of 452 days 8 . To date, there are no published data available which describe clinical outcomes of SRT for INC in cats.…”

“…Intranasal carcinomas (INC) in cats are typically locally invasive and slow to metastasize to locoregional lymph nodes, other organs (ie, lungs), or both 4,5 . Since complete excision cannot be achieved with surgery, and chemotherapy alone has minimal efficacy for the treatment of gross disease, 6,7 external beam radiotherapy (RT) is generally regarded as the treatment of choice for INC in cats; however, there is a paucity of published data describing clinical outcomes after treatment with modern irradiation protocols 4,8 …”

“…Cats with INC treated with 10 daily (Monday-Friday) fractions of 4.2 Gy, and 89% of cats were treated with IMRT-based treatment plans had median OST of 269 days while 11% treated with more traditional 3D conformal radiation therapy (3D-CRT) methods had median OST of 452 days. 8 To date, there are no published data available which describe clinical outcomes of SRT for INC in cats. The goal of this multi-institutional retrospective study was to evaluate clinical outcomes in cats with INC that were treated with various palliative-and definitive-intent irradiation protocols, and to identify factors which might aid in predicting treatment outcomes.…”