Radioprotective Effect of Vitamin E in Parotid Glands: a Morphometric Analysis in Rats

The aim of this study was to evaluate the radioprotective effect of vitamin E on rat parotid glands by morphometric analysis. Sixty male rats were divided into 5 groups (n=6): control, in which animals received olive oil solution; olive oil/irradiated, in which animals received olive oil and were irradiated with a dose of 15 Gy of gamma radiation; irradiated, in which animals were irradiated with a dose of 15 Gy gamma radiation; vitamin E, which received α-tocopherol acetate solution; vitamin E/irradiated, which received α-tocopherol acetate solution before irradiation with a dose of 15 Gy gamma rays. Half of the animals were euthanized at 8 h, and the remaining at 30 days after irradiation. Both parotid glands were surgically removed and morphometric analysis of acinar cells was performed. Data were subjected to two-way ANOVA and Tukey's test (α=0.05). Morphometric analysis showed a significant reduction in the number of parotid acinar cells at 30 days in olive oil/irradiated and irradiated groups. In groups evaluated over time a significant reduction was shown at 30 days in olive oil/irradiated and irradiated groups, indicating that ionizing radiation caused tissue damage. The vitamin E/irradiated group presented more acinar cells than the irradiated group, but no statistically significant difference was observed (p>0.05). In conclusion, vitamin E seems to have failed as a radioprotective agent on acinar cells in rat parotid glands.

O objetivo neste estudo foi avaliar o efeito radioprotetor da vitamina E sobre glândulas parótidas de ratos por meio de análise morfométrica. Sessenta ratos machos foram divididos em cinco grupos: controle, no qual os animais receberam solução de óleo de oliva; óleo de oliva irradiado, em que os animais receberam óleo de oliva e foram irradiados com uma dose de 15 Gy de radiação gama; irradiado, em que os animais foram irradiados com uma dose de 15 Gy de radiação gama; vitamina E, no qual receberam solução de acetato α-tocoferol; vitamina E irradiado, os quais receberam solução de acetato de α-tocoferol antes da irradiação com uma dose de 15 Gy de radiação gama. Metade dos animais foi eutanasiada em 8 h, e o restante aos 30 dias após a irradiação. Ambas as glândulas parótidas foram removidas cirurgicamente e análise morfométrica das células acinares foi realizada. Os dados foram submetidos à Análise de Variância com 2 fatores e teste de Tukey (α=0,05). A análise morfométrica mostrou uma redução significativa no número de células acinares da glândula parótida aos 30 dias nos grupos óleo irradiado e irradiado. Nos grupos avaliados ao longo do tempo uma redução significativa foi mostrada aos 30 dias nos grupos óleo irradiado e irradiado, indicando que a radiação ionizante causou danos teciduais. O grupo vitamina E/irradiado apresentou mais células acinares que o grupo irradiado, mas diferença estatisticamente significante não foi observada. Em conclusão, a vitamina E parece ter fracassado como um agente radioprotetor nas células acinares das glândulas parótidas de ratos.

Acinic cell carcinoma of the salivary glands: a literature review

Acinic cell carcinoma [ACC] is a low-grade malignant salivary neoplasm that constitutes approximately 17% of primary salivary gland malignancies. In the head and neck region, the parotid gland is the preddominant site of origin and women are usually more frequently diagnosed than men. Previous radiation exposure and familial predisposition are some of the risk factors for ACC. A slowly enlarging mass lesion in the tail of the parotid gland is the most frequent presentation. The diagnosis is usually confirmed with a fine needle aspiration biopsy, and surgical excision is the main treatment of this malignant neoplasm. Other treatment modalities such as radiotherapy may be indicated in some cases. ACC has a significant tendency to recur, to produce metastases [cervical lymph nodes and lungs], and may have an aggressive evolution. Therefore, long-term follow-up is mandatory after treatment

Multi-institutional Comparison of Intensity Modulated Radiation Therapy (IMRT) Planning Strategies and Planning Results for Nasopharyngeal Cancer

The intensity-modulated radiation therapy (IMRT) planning strategies for nasopharyngeal cancer among Korean radiation oncology facilities were investigated. Five institutions with IMRT planning capacity using the same planning system were invited to participate in this study. The institutions were requested to produce the best plan possible for 2 cases that would deliver 70 Gy to the planning target volume of gross tumor (PTV1), 59.4 Gy to the PTV2, and 51.5 Gy to the PTV3 in which elective irradiation was required. The advised fractionation number was 33. The planning parameters, resultant dose distributions, and biological indices were compared. We found 2-3-fold variations in the volume of treatment targets. Similar degree of variation was found in the delineation of normal tissue. The physician-related factors in IMRT planning had more influence on the plan quality. The inhomogeneity index of PTV dose ranged from 4 to 49% in Case 1, and from 5 to 46% in Case 2. Variation in tumor control probabilities for the primary lesion and involved LNs was less marked. Normal tissue complication probabilities for parotid glands and skin showed marked variation. Results from this study suggest that greater efforts in providing training and continuing education in terms of IMRT planning parameters usually set by physician are necessary for the successful implementation of IMRT.

Effect of ionizing radiation on rat parotid gland

A common side effect of radiotherapy used in the treatment of oral cancer is the occurrence of structural and physiological alterations of the salivary glands due to exposure to ionizing radiation, as demonstrated by conditions such as decreased salivary flow. The present study evaluated ultrastructural alterations in the parotid glands of rats receiving a fractionated dose (1,500-cGy) of radiation emitted by a Cesium-137 source and rats that were not subjected to ionizing radiation. After sacrifice, the parotid glands were removed and examined by transmission electron microscopy. Damage such as cytoplasmic vacuolization, dilatation of the endoplasmic reticulum and destruction of mitochondria, as well as damage to the cellular membrane of acinar cells, were observed. These findings lead to the conclusion that ionizing radiation promotes alterations in the glandular parenchyma, and that these alterations are directly related to the dose level of absorbed radiation. Certain phenomena that appear in the cytoplasm and nuclear material indicate that ionizing radiation causes acinar cell death (apoptosis).

Um efeito colateral comum da radioterapia usada no tratamento de câncer na cavidade oral é a ocorrência de alterações estruturais e fisiológicas sobre as glândulas salivares por exposição à radiação ionizante, como demonstrada em situações com decréscimo do fluxo salivar. O presente estudo teve por objetivo avaliar as alterações ultra-estruturais de glândulas parótidas de ratos que receberam uma dose fracionada (1500 - cGy) de radiação emitida por uma fonte de Césio 137 e ratos que não receberam a radiação ionizante. Após o sacrifício, as glândulas parótidas foram removidas e examinadas por microscopia eletrônica de transmissão. Lesões das organelas citoplasmáticas, como dilatação do retículo endoplasmático, destruição das mitocôndrias e formação das vacuolizações citoplasmáticas, além de lesão da membrana celular das células acinares foram observadas. Portanto, a radiação ionizante promove alterações no parênquima glandular, o que está diretamente relacionado com a dose de radiação absorvida. Determinados fenômenos que surgem no citoplasma e material nuclear são indicadores de que a radiação ionizante leva a célula acinar a morte programada (apoptose).

Evaluation of radiotherapy effect on major salivary glands in head and neck cancer patients by ultrasonography

In 15 patients, the acute parotid inflammatory and degenerative changes appearing shortly after irradiation were sonographically expressed as decreased echogenicity and haziness of the gland contour. In 13 patients, examined 3 years after irradiation, reduction in the gland size as well as diffuse coarse parenchymal pattern with linear areas of echogenicity were demonstrable. This reflects the underlying fibrosis and parenchymal atrophy. Sonography may therefore help in evaluating acute and chronic radiation-induced salivary gland damage

Estudo histomorfológico da glândula parótida de rato jovem, submetida à radiaçäo ionizante / Histomorphologic study of the parotid glands of young rats exposed of ionizing radiation

Foram utilizados 30 ratos (Holtzman) com 25 dias de idade, com o objetivo de avaliar os efeitos da radiaçäo ionizante sobre as estruturas das glândulas parótidas de ratos jovens. Os animais foram distribuídos eqüitativamente em dois grupos experimentais: Grupo I, irradiado; e Grupo II, controle. Utilizando um aparelho de radioterapia convencional, a regiäo ao nível das glândulas parótidas foi irradiada com uma dose de 300 R, sendo o procedimento repetido a cada 48 horas, totalizando uma exposiçäo de 1200 R. Decorridos os períodos de 3, 8, 13, 18 e 28 dias, os animais de ambos os grupos foram sacrificados e as glândulas parótidas removidas e fixadas em formol a 10 por cento e líquido de Bouin, por 24 horas. Os cortes foram corados pela hematoxilina e eosina e Tricrômico de Mallory, permitindo análise pela microscopia óptica comum. Com base na metodologia empregada concluiu-se que: os ratos do grupo irradiado ganharam peso corporal uniforme a partir do 13§ dia, embora näo equivalente ao do grupo controle respectivamente; a fase crítica de desorganizaçäo glandular determinada pela radiaçäo correspondeu ao período de 8 dias, decrescendo nos seqüentes; os ácinos serosos e os ductos estriados mostraram-se mais radiosensíveis, mesmo com o uso de dose baixa e fracionada; a glândula parótida apresentou sinais de reparaçäo morfológica à medida que se distanciou da última exposiçäo aos raios X