Prognostic factors for cats with squamous cell carcinoma of the nasal planum following high-dose rate brachytherapy
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2017
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O carcinoma de células escamosas (SCC) é um dos tumores malignos mais comuns da pele dos gatos. A incidência é maior em gatos com pêlo de cor clara, falta de pigmento e áreas de pêlo escasso ou sem pêlo, e as orelhas, pálpebras, plano nasal e têmporas são as áreas mais afetadas, sendo mais comum nos gatos mais velhos. A exposição solar crónica é considerada o fator indutor da carcinogénese: induz alterações actínicas na pele que evoluem para lesões pré-neoplásicas, carcinoma in situ e SCC invasivo. O diagnóstico definitivo é feito por biópsia.
Como a taxa de metastização do SCC do plano nasal é muito baixa, e dado o seu caráter localmente invasivo, o principal objetivo do tratamento é o controlo local do tumor. Várias modalidades de tratamento são utilizadas no maneio deste tumor, mas com resultados pouco satisfatórios. A radioterapia externa tem sido usada nos últimos anos com melhores resultados nos tempos de recidiva e sobrevida global. A braquiterapia de alta dosagem (HDR) é um tratamento de radioterapia de contacto, com um curto período de tratamento global e um efeito poupador dos tecidos não neoplásicos.
Devido à falta de literatura sobre braquiterapia HDR no tratamento deste tumor, este estudo retrospetivo foi realizado para descobrir se existiam variáveis individuais e do tumor que pudessem ser fatores de prognóstico para a sobrevida livre de progressão (PFS) e sobrevida global (OS). Os dados recolhidos são referentes a 58 gatos com SCC do plano nasal tratados com braquiterapia HDR, e incluem: género, estado reprodutivo, raça, idade, número de lesões, localização e tamanho do tumor, extensão do tumor para além do plano nasal, ulceração, metástases ganglionares e pulmonares, qualquer tratamento prévio, resposta à braquiterapia HDR, recidiva e sobrevida global.
A dose total de radiação foi 30 Gy, administrada em cinco frações de 6 Gy, durante 3 a 4 dias. Resposta completa foi alcançada em 72% (n=36) dos gatos, resposta parcial em 26% (n=13) e 2% (n=1) não responderam. A média dos tempos de PFS e OS foram 316 e 835 dias, respetivamente. O sexo dos gatos tratados com braquiterapia HDR afetou o tempo de OS (p=0,045): os machos viveram menos tempo. O tamanho do tumor mostrou um efeito significativo na resposta ao tratamento (p=0,015) e na OS (p=0,001): gatos com tumores iguais ou menores que 2 cm responderam melhor ao tratamento e viveram mais tempo. Os gatos sem progressão tumoral para o lábio superior viveram mais tempo (p=0,015). Os gatos que receberam outro tratamento antes da braquiterapia HDR apresentaram tempos de PFS menores. Finalmente, a resposta do tumor à braquiterapia HDR estava estatisticamente associada à PFS (p=0,038) e OS (p<0,001): gatos que responderam melhor apresentaram melhores tempos de controlo local do tumor e viveram mais tempo.
Concluindo, as lesões devem ser tratadas o mais rápido possível e podem ser obtidos resultados muito bons com a braquiterapia HDR no que diz respeito à PFS, OS e resultados cosméticos.
Squamous cell carcinoma (SCC) is one of the most common malignant tumors of the cats’ skin. Higher incidence rates are associated to cats with light-colored fur, lack of protective pigment, and sparsely haired / hairless areas, and so ears, eyelids, nasal planum and temples are most affected areas, and older cats are the most affected. Chronic sunlight exposure is considered the inducing factor of carcinogenesis: it leads to actinic changes on the skin that evolve into pre-neoplastic lesions, carcinoma in situ and finally invasive SCC. Definitive diagnosis is achieved with biopsy. As the metastatic rate of nasal planum SCC is very low, and given its locally invasive character, the main goal of the treatment is to achieve the best local control of the tumor. Several treatment modalities have been used to manage this tumor but with unsatisfactory outcomes. External radiotherapy has been used over the last years with better results on recurrence times and overall survival. High-dose rate (HDR) brachytherapy is a short-distance radiotherapy treatment, with a short overall treatment time and a sparing effect of the non-neoplastic tissues. Because of the lack in the literature on HDR brachytherapy to treat this tumor, this retrospective study was performed to find out if there were any individual and tumor’s variables that could be prognostic factors for progression-free survival (PFS) and overall survival (OS). Data collected from clinical records of 58 cats with SCC of the nasal planum treated with HDR brachytherapy included: gender, neuter status, breed, age, number of lesions, localization and size of the tumor, tumor extension beyond the nasal planum, ulceration, lymph node and lung metastases, any previous treatment, tumor response to HDR brachytherapy, recurrence and overall survival. The total radiation dose delivered was 30 Gy, administered in five fractions of 6 Gy for a period of 3 to 4 days. Complete response was achieved in 72% (n=36) of the cats, partial response in 26% (n=13) and 2% (n=1) did not respond. Median PFS and OS times were 316 and 835 days, respectively. The gender of the cats treated with HDR brachytherapy affected OS time (p=0.045), with male cats living less. Tumor size showed a significant effect on tumor response (p=0.015) and on OS (p=0.001), so cats with tumors equal or smaller than 2 cm achieved better treatment responses and lived longer than cats with larger lesions. Results also reported that cats without tumor extension to the upper lip lived longer (p=0.015). Cats that received other treatment before HDR brachytherapy showed shorter PFS times. Finally, tumor response to HDR brachytherapy was found to be statistically associated with PFS (p=0.038) and OS (p<0.001), so cats with better tumor responses showed better local tumor control times and lived longer. In conclusion, lesions should be treated as soon as possible and can be achieved very good results with HDR brachytherapy in what concerns to PFS, OS and cosmetic outcomes.
Squamous cell carcinoma (SCC) is one of the most common malignant tumors of the cats’ skin. Higher incidence rates are associated to cats with light-colored fur, lack of protective pigment, and sparsely haired / hairless areas, and so ears, eyelids, nasal planum and temples are most affected areas, and older cats are the most affected. Chronic sunlight exposure is considered the inducing factor of carcinogenesis: it leads to actinic changes on the skin that evolve into pre-neoplastic lesions, carcinoma in situ and finally invasive SCC. Definitive diagnosis is achieved with biopsy. As the metastatic rate of nasal planum SCC is very low, and given its locally invasive character, the main goal of the treatment is to achieve the best local control of the tumor. Several treatment modalities have been used to manage this tumor but with unsatisfactory outcomes. External radiotherapy has been used over the last years with better results on recurrence times and overall survival. High-dose rate (HDR) brachytherapy is a short-distance radiotherapy treatment, with a short overall treatment time and a sparing effect of the non-neoplastic tissues. Because of the lack in the literature on HDR brachytherapy to treat this tumor, this retrospective study was performed to find out if there were any individual and tumor’s variables that could be prognostic factors for progression-free survival (PFS) and overall survival (OS). Data collected from clinical records of 58 cats with SCC of the nasal planum treated with HDR brachytherapy included: gender, neuter status, breed, age, number of lesions, localization and size of the tumor, tumor extension beyond the nasal planum, ulceration, lymph node and lung metastases, any previous treatment, tumor response to HDR brachytherapy, recurrence and overall survival. The total radiation dose delivered was 30 Gy, administered in five fractions of 6 Gy for a period of 3 to 4 days. Complete response was achieved in 72% (n=36) of the cats, partial response in 26% (n=13) and 2% (n=1) did not respond. Median PFS and OS times were 316 and 835 days, respectively. The gender of the cats treated with HDR brachytherapy affected OS time (p=0.045), with male cats living less. Tumor size showed a significant effect on tumor response (p=0.015) and on OS (p=0.001), so cats with tumors equal or smaller than 2 cm achieved better treatment responses and lived longer than cats with larger lesions. Results also reported that cats without tumor extension to the upper lip lived longer (p=0.015). Cats that received other treatment before HDR brachytherapy showed shorter PFS times. Finally, tumor response to HDR brachytherapy was found to be statistically associated with PFS (p=0.038) and OS (p<0.001), so cats with better tumor responses showed better local tumor control times and lived longer. In conclusion, lesions should be treated as soon as possible and can be achieved very good results with HDR brachytherapy in what concerns to PFS, OS and cosmetic outcomes.
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Dissertação de Mestrado Integrado em Medicina Veterinária
Palavras-chave
Carcinoma de células escamosas , Mucosa nasal , Braquiterapia , Prognóstico , Gatos