Intensity modulated radiotherapy (IMRT) or conformational radiotherapy (3D-CRT) with conventional fractionation for prostate cancer: Is there any clinical difference?

ABSTRACT Purpose: To compare the treatment outcomes of a cohort of prostate cancer patients treated with conventional schedule using IMRT or 3DRT technique. Materials and Methods: Between 2010-2017, 485 men with localized prostate cancer were treated with conventional radiotherapy schedule with a total dose ≥74Gy using IMRT (231) or 3DCRT (254). Late gastrointestinal (GI) and genitourinary (GU) toxicity were retrospectively evaluated according to modified RTOG criteria. The biochemical control was defined by the Phoenix criteria (nadir + 2ng/mL). The comparison between the groups included biochemical recurrence free survival (bRFS), overall survival (OS) and late toxicity. Results: With a median follow-up of 51 months (IMRT=49 and 3DRT=51 months), the maximal late GU for >=grade- 2 during the entire period of follow-up was 13.1% in the IMRT and 15.4% in the 3DRT (p=0.85). The maximal late GI ≥ grade- 2 in the IMRT was 10% and in the 3DRT 24% (p=0.0001). The 5-year bRFS for all risk groups with IMRT and 3D-CRT was 87.5% vs. 87.2% (p=0.415). Considering the risk-groups no significant difference for low-, intermediate- and high-risk groups between IMRT (low-95.3%, intermediate-86.2% and high-73%) and 3D-CRT (low-96.4%, intermediate-88.2% and high-76.6%, p=0.448) was observed. No significant differences for OS and DMFS were observed comparing treatment groups. Conclusion: IMRT reduces significantly the risk of late GI severe complication compared with 3D-CRT using conventional fractionation with a total dose ≥74Gy without any differences for bRFS and OS.

Cosmesis in patients with breast neoplasia submitted to the hypofractionated radiotherapy with of intensity-modulated beam

SUMMARY OBJECTIVE: To assess the cosmetic satisfaction of patients diagnosed with breast cancer submitted to the hypofractionated radiotherapy with IMRT (hIMRT) technique and its correlation with dosimetric data of the radiotherapy planning. MATERIALS AND METHODS: The retrospective cohort study that assessed women with a diagnosis of malignant breast neoplasia submitted to the conservative treatment or radical mastectomy and treated with hIMRT. In the period between August 2007 to December 2014, in a philanthropic / private institution, 170 records were selected. The cosmetic assessment was carried out by means of the Harvard/RTOG/NSABP scale with one-year minimum range after treatment. The collected dosimetric data were: breast / chest wall volume, volume that received 95% (V95%) and 107% (V107%) of the prescribed dose. RESULTS: The volume of the treated breasts ranged from 169 to 2.103 ml (median = 702; IQR: 535 to 914 ml). Median V95% was 86.7% (54.6-96.6%; IQR: 80.0% to 90.6%); eight (5.7%) patients had V95% higher than 95%. Median V107% was 0% (0%-16.3%; IQR: 0.0% to 0.3% and 13); 9.3% patients had V107% higher than 2%. One hundred and thirty-three (78.2%) patients responded to the cosmetic assessment: 99 (74.4%) considered the cosmetic results excellent. Significant associations between cosmetic assessment and breast volume (p=0.875), V95% (p=0.294) e V107% (p=0.301) were not found. CONCLUSION: The cosmetic results showed favorable when using hIMRT, and the lack of correlation with usual the dosimetric data illustrates the capacity of hIMRT to minimize the heterogeneity of the dose in this endpoint, even in voluminous breasts.

RESUMO OBJETIVO: Avaliar a satisfação cosmética de pacientes diagnosticadas com câncer de mama submetidas à radioterapia hipofracionada com técnica IMRT (hIMRT) e sua correlação com dados dosimétricos do planejamento radioterápico. MATERIAIS E MÉTODOS: Estudo de coorte retrospectivo que avaliou mulheres com diagnóstico de neoplasia maligna de mama submetidas a tratamento conservador ou mastectomia radical e tratadas com hIMRT. No período de agosto de 2007 a dezembro de 2014, em uma instituição filantrópica/particular, foram selecionados 170 prontuários. A avaliação cosmética foi feita por meio da escala de Harvard/RTOG/NSABP com um intervalo mínimo de um ano após o tratamento. Dados dosimétricos coletados foram: volume da mama/plastrão, volume que recebeu 95% (V95%) e 107% (V107%) da dose prescrita. RESULTADOS: O volume das mamas tratadas variou de 169 a 2.103 ml (mediana = 702; IQR: 535 a 914 ml). O V95% mediano foi 86,7% (54,6-96,6%; IQR: 80,0% a 90,6%); oito (5,7%) pacientes tiveram o V95% superior a 95%. O V107% mediano foi 0% (0%-16,3%; IQR: 0,0% a 0,3% e 13); 9,3% pacientes tiveram o V107% superior a 2%. Cento e trinta e três (78,2%) pacientes responderam à avaliação cosmética: 99 (74,4%) consideraram o resultado cosmético excelente. Não foram encontradas associações significativas entre a avaliação cosmética e o volume da mama (p=0,875), V95% (p=0,294) e V107% (p=0,301). CONCLUSÕES: Os resultados cosméticos mostraram-se favoráveis com o uso de hIMRT, e a ausência de correlação com os dados dosimétricos usuais ilustra a capacidade do hIMRT em minimizar a heterogeneidade da dose neste desfecho, mesmo em mamas volumosas.

Intensity-modulated radiation therapy (IMRT) versus 3-dimensional conformal radiation therapy (3D-CRT) for head and neck cancer: cost-effectiveness analysis

SUMMARY BACKGROUND: A cost-effectiveness analysis of IMRT compared to 3D-CRT for head and neck cancer patients (HNCPs) was conducted in the Brazilian Public Health System. METHODS: A Markov model was used to simulate radiation therapy-induced dysphagia and xerostomia in HNCPs. Data from the PARSPORT trial and the quality-of-life study were used as parameters. The incremental cost-effectiveness ratio (ICER) and cost per quality-adjusted life-year (QALY) gained were calculated. RESULTS: At 2 years, IMRT was associated with an incremental benefit of 0.16 QALYs gained per person, resulting in an ICER of BRL 31,579 per QALY gained. IMRT was considered cost-effective when using the guideline proposed by the World Health Organization (WHO) of three times the national gross domestic product (GDP) per capita (BRL 72,195). Regarding life expectancy (15 years), the incremental benefit of IMRT was 1.16 QALYs gained per person, with an ICER of BRL 4,341. IMRT was also cost-effective using the WHO definition, which states that the maximum cost is equal to the GDP per capita (BRL 24,065). CONCLUSIONS: IMRT was considered cost-effective from the perspective of the Brazilian public health system.

RESUMO INTRODUÇÃO: Foi realizada uma análise de custo-efetividade da radioterapia com intensidade modulada de feixe (IMRT) comparada com a radioterapia conformada para pacientes com câncer de cabeça e pescoço (CCP) no contexto do Sistema Único de Saúde (SUS). MÉTODOS: Foi elaborado um modelo de Markov para comparar os custos médicos diretos e os desfechos de saúde relacionados à qualidade de vida do paciente pós-intervenção radioterápica sofrendo de xerostomia e disfagia. Com essa finalidade, foram usados os dados do estudo PARSPORT e parâmetros de qualidade de vida. Os resultados comparativos das estratégias alternativas de tratamento foram medidos pela razão de custo-efetividade incremental (RCEI). O desfecho analisado foi o de anos de vida ajustados à qualidade (QALY). RESULTADOS: Em um horizonte de tempo de dois anos, a IMRT foi associada com um benefício incremental de ganho de 0,16 QALYs por indivíduo, resultando em um RCEI de R$ 31.579 por QALY ganhado. A IMRT foi custo-efetivo, adotando-se o limite máximo de disposição a pagar, proposto pela OMS, de três vezes o PIB per capita nacional, equivalente a R$ 72.195. No horizonte de tempo de 15 anos, o benefício incremental de ganho foi de 1,16 QALYs por indivíduo, com um RCEI de R$ 4.341. A IMRT foi custo-efetivo, adotando-se o limite de disposição a pagar, proposto pela OMS, de uma vez o PIB per capita nacional, equivalente a R$ 24.065. CONCLUSÃO: A IMRT foi considerada um tratamento custo-efetivo na perspectiva do SUS.

Radioterapia de intensidade modulada (IMRT) para o tratamento de tumores de cabeça e pescoço em estágio inicial e localmente avançado / Intensity modulated radiation therapy (IMRT) for the treatment of early and locally advanced head and neck tumors

CONTEXTO: O tumor de cabeça e pescoço é um grupo heterogêneo de doenças incluindo tumores com diversos tipos histológicos, de cavidade oral, faringe, laringe, narinas, seios paranasais, tireoide, glândulas salivares. A radioterapia tem como importante efeito adverso a lesão de estruturas nobres como glândulas submandibulares e parótidas. TECNOLOGIA: Radioterapia por Intensidade Modulada (IMRT). INDICAÇÃO: Tumores de Cabeça e Pescoço. PERGUNTA: A técnica de radioterapia por IMRT é mais eficaz e segura do que as modalidades de radioterapia convencional (2D) ou tridimensional (3D)? EVIDÊNCIAS CIENTÍFICAS: os estudos apresentam baixa qualidade, demonstrando superioridade apenas em relação a xerostomia observada pelo médico. Existe dúvida em relação ao risco de neoplasias secundárias, com provável aumento do risco. A implementação apresenta dificuldades como adaptação do ambiente, treinamento da equipe e maior duração de cada seção. AVALIAÇÃO ECONÔMICA: elevado valor estimado de RCEI R$ 574.087,00/QALY. AVALIAÇÃO DE IMPACTO ORÇAMENTÁRIO: anual R$ 67.152.510,00 e em 5 anos R$ 335.762.550,00. DISCUSSÃO: As vantagens são incertas, o procedimento é mais longo e existe risco de incremento em neoplasias secundárias, sem impacto favorável em sobrevida. RECOMENDAÇÃO DA CONITEC: A matéria será disponibilizada em Consulta Pública com recomendação preliminar não favorável. CONSULTA PÚBLICA: Ao considerar os riscos e benefícios potenciais da tecnologia, a matéria foi disponibilizada em Consulta Pública com recomendação da Conitec não favorável. Após a análise das 138 contribuições recebidas na Consulta Pública, a Conitec deliberou por recomendar a não incorporação da radioterapia de intensidade modulada (IMRT) para o tratamento de tumores de cabeça e pescoço em estágio inicial e localmente avançado. DELIBERAÇÃO FINAL: Os membros presentes deliberaram por unanimidade recomendar a não incorporação de um procedimento específico para radioterapia de intensidade modulada (IMRT) para o tratamento de tumores de cabeça e pescoço em estágio inicial e localmente avançado. Foi assinado o Registro de Deliberação n˚174/2015. A recomendação será encaminhada para decisão do Secretário da SCTIE. O representante do CFM se absteve de votar por alegar conflito de interesse com o tema. DECISÃO: Não incorporar de procedimento específico para radioterapia de intensidade modulada (IMRT) para o tratamento de tumores de cabeça e pescoço em estágio inicial e localmente avançado, no âmbito do Sistema Único de Saúde ­ SUS, dada pela Portaria SCTIE-MS nº 7 publicada no Diário Oficial da União (D.O.U.) nº 18, de 27 de janeiro de 2016, pág. 57.(AU)

Challenges of Ionizing Radiation in Tumor Treatment and Role of Angiogenesis.

Ionizing radiation is a non-specific, but most widely used therapeutic method for cancer treatment. However, a minor fraction of tumor cell population manages to survive after radiation. Radiation efficacy depends on adequate oxygen supply. Rapid growing tumors cause hypoxia that upregulates many pro-survival pathways. At clinical doses, radiation activates inflammatory pathways and causes oxidative stress that plays a positive role during angiogenesis. Selective targeting of signaling mechanisms may radiosensitize tumors.

External beam radiation therapy and a low-dose-rate brachytherapy boost without or with androgen deprivation therapy for prostate cancer

Purpose To assess outcomes with external beam radiation therapy (EBRT) and a low-dose-rate (LDR) brachytherapy boost without or with androgen deprivation therapy (ADT) for prostate cancer. Materials and Methods From January 2001 through August 2011, 120 intermediate-risk or high-risk prostate cancer patients were treated with EBRT to a total dose of 4,500 cGy in 25 daily fractions and a palladium-103 LDR brachytherapy boost of 10,000 cGy (n = 90) or an iodine-125 LDR brachytherapy boost of 11,000 cGy (n = 30). ADT, consisting of a gonadotropin-releasing hormone agonist ± an anti-androgen, was administered to 29/92 (32%) intermediate-risk patients for a median duration of 4 months and 26/28 (93%) high-risk patients for a median duration of 28 months. Results Median follow-up was 5.2 years (range, 1.1-12.8 years). There was no statistically-significant difference in biochemical disease-free survival (bDFS), distant metastasis-free survival (DMFS), or overall survival (OS) without or with ADT. Also, there was no statistically-significant difference in bDFS, DMFS, or OS with a palladium-103 vs. an iodine-125 LDR brachytherapy boost. Conclusions There was no statistically-significant difference in outcomes with the addition of ADT, though the power of the current study was limited. The Radiation Therapy Oncology Group 0815 and 0924 phase III trials, which have accrual targets of more than 1,500 men, will help to clarify the role ADT in locally-advanced prostate cancer patients treated with EBRT and a brachytherapy boost. Palladium-103 and iodine-125 provide similar bDFS, DMFS, and OS. .

We should not settle for low-level evidence but should always use the best available evidence / 부인종양

No abstract available.

Shall we settle for low-level evidence? / 부인종양

No abstract available.

Efectividad y seguridad de la radioterapia conformacional en cáncer gástrico / Effectiveness and safety of conformational radiotherapy in gastric cancer

Antecedentes: Descripción de la condición de salud de interés: El cáncer gástrico es el cuarto cáncer más común en el mundo, y es la segunda causa de muerte por cáncer a nivel mundial. Su incidencia varía en forma importante de un país a otro. Colombia se encuentra entre los países con las tasas más altas, con aproximadamente 7.700 nuevos casos diagnosticados en el 2007, y representa la primera causa de muerte por tumores malignos en ambos sexos. Según estadísticas de GLOBOCAN 2008, se estima una tasa de incidencia anual de 17.4/100.000 personas. Entre 90% y 95% de los tumores malignos del estómago son adenocarcinomas, y los grupos de edad más afectados son los de la séptima y la octava décadas de la vida (promedio de 65 años), pero si se considera sólo en pacientes con diagnóstico en etapa precoz (cáncer incipiente), la edad promedio desciende a 40-45 años. En Colombia, en más de la mitad de los pacientes con cáncer gástrico, el diagnóstico se hace en los estadios avanzados de la enfermedad. Descripción de la tecnología: Descripción de la tecnología: La radioterapia es una técnica que consiste en la exposición \r\nde los tejidos a radiaciones ionizantes. Se utilizan fuentes naturales o artificiales de radiación. El mecanismo de acción a nivel celular es la producción de radicales libres, los cuales son nocivos para las estructuras vitales de las células. Evaluación de efectividad y seguridad: Pregunta de evaluación: En pacientes adultos con cáncer gástrico ¿cuál es la efectividad y seguridad de la la radioterapia conformacional 3D en comparación con la radioterapia convencional (AP-PA), en cubrimiento de volumen blanco y toxicidad en \r\ntejido normal (órganos en riesgo)? La pregunta de investigación fue validada teniendo en uenta las siguientes fuentes de información: registro sanitario INVIMA, Acuerdo 029 de 2011, guías de práctica clínica, \r\nrevisiones sistemáticas y narrativas de la literatura, estudios de prevalencia/incidencia y carga de enfermedad, libros de texto, consulta con expertos temáticos, sociedades científicas y otros actores clave. Población: Pacientes con diagnóstico de cáncer gástrico. Tecnología de interés: Radioterapia conformacional 3D. Metodología: Búsqueda de literatura, Búsqueda en bases de datos electrónicas. Conclusiones: Efectividad: la radioterapia conformacional 3D en comparación con la técnica convencional AP-PA, ha demostrado ser una técnica efectiva para el tratamiento adyuvante de pacientes con cáncer gástrico, con resultados que demuestran que esta técnica ofrece un mejor cubrimiento de órgano blanco. Seguridad: \r\nen órganos adyacentes en riesgo de irradiación, la radioterapia conformacional 3D ha demostrado una menor dosis de irradiación en columna vertebral, riñón izquierdo y riñón derecho. Para el hígado, las dosis de irradiación son mayores con la radioterapia conformacional 3D en comparación con la radioterapia convencional; sin embargo, dichas dosis se encuentran aún por debajo de la dosis hepática tolerada.

Análisis del volumen rectal en pacientes con cáncer de próstata: temprano durante la radioterapia conformada / Analysis of rectal volume in patients with early prostate cancer: during the 3D radiation therapy

Se realiza un estudio observacional, descriptivo y cuantitativo, con descripción numérica de los datos, con el objetivo de determinar el cambio del volumen rectal en noventa pacientes con cáncer de próstata durante el tratamiento radiante. Utilizamos técnica de radioterapia conformada y tres dimensiones. El método complementario elegido para valorar el cambio del volumen de la ampolla rectal fue una tomografía axial computarizada de pelvis durante el tratamiento radiante. En el 86% de pacientes se evidenció la ampolla rectal con material fecal y gaseoso; y en 14% restante se encontraba vacía. Los diámetros promedios fueron de: 23,4 mm para ampolla rectal vacía y 32,8 mm para la ampolla rectal dilatada, los cambios del volumen rectal alteran la posición del volumen blanco de tratamiento radiante (próstata). Recomendamos efectuar la radioterapia entre las 15 y las 18 horas de acuerdo a la fisiología y practicar a todo paciente una manometría ano-rectal.

We realized a study observational, descriptive and quantitative with numeric description of date, we carry out this work to determine the change of rectal volume in 90 patients with diagnostic of prostate cancer during radiant treatment. We utilize conformal radiation therapy technique in tree dimension. The complementary method used to valor the changes in the volume of the rectal was axial computer tomography of the pelvis during the radiation treatment. In 86% of patients we evidence the rectal blister with fecal and gaseous material the rest 14% blister was empty. The average of diameters were 23.4 mm to the blister empty and 38.8 mm to the rectal dilated blister, the changes in the rectal volume alter the volume target of the radiation treatment (prostate). Recommend do the radiation therapy between the 15 and 18 hours in relation with physiology and practice to all patients a rectal manometer study.

Radiotherapy and radiosurgery for Cushing's disease

Patients with residual or recurrent Cushing's disease receive external beam radiotherapy (RT) with the aim of achieving long-term tumour control and normalization of elevated hormone levels. Treatment is given either as conventional radiotherapy using conformal techniques or as stereotactic radiotherapy, which is either used as fractionated treatment (SCRT) or as single fraction radiosurgery (SRS). We describe the technical aspects of treatment and report a systematic review of the published literature on the efficacy and toxicity of conventional RT, SCRT and SRS. There are no studies directly comparing the different radiation techniques and the reported results are inevitably of selected patients by investigators with interest in the treatment tested. Nevertheless the review of the published literature suggests better hormone and tumour control rates after fractionated irradiation compared to single fraction radiosurgery. Hypopituitarism represents the most commonly reported late complication of radiotherapy seen after all treatments. Although the incidence of other late effects is low, the risk of radiation injury to normal neural structures is higher with single fraction compared to fractionated treatment. Stereotactic techniques offer more localized irradiation compared with conventional radiotherapy, however longer follow-up is necessary to confirm the potential reduction of long-term radiation toxicity of fractionated SCRT compared to conventional RT. On the basis of the available literature, fractionated conventional and stereotactic radiotherapy offer effective treatment for Cushing's disease not controlled with surgery alone. The lower efficacy and higher toxicity of single fraction treatment suggest that SRS is not the appropriate therapy for the majority of patients with Cushing's disease.

Pacientes com doença de Cushing residual ou recorrente recebem radioterapia externa em feixe (RT) com o objetivo de alcançar um controle tumoral prolongado e a normalização dos níveis hormonais elevados. O tratamento é realizado tanto com RT convencional, usando técnicas conformacionais, ou com RT estereotáxica, que é usada tanto como tratamento fracionado (RTF) ou como radiocirurgia em procedimento único (RCU). Descreveremos os aspectos técnicos do tratamento e mostraremos uma revisão sistemática da literatura sobre a eficácia e toxicidade da RT convencional, da RTF e da RCU. Não existem estudos comparando diretamente as diferentes técnicas de radiação, e os resultados reportados são inevitavelmente os de pacientes selecionados pelos investigadores com interesse no tratamento testado. De qualquer maneira, a revisão dos dados publicados sugere que há melhores taxas de controle hormonal e tumoral após RTF em comparação com RCU. O hipopituitarismo representa a complicação tardia mais comumente relatada da RT, vista após todos os tipos de tratamento. Embora a incidência de outros efeitos tardios seja baixa, o risco de a radiação comprometer estruturas neurais normais é mais elevado com RCU do que com RTF. Técnicas estereotáxicas oferecem irradiação mais localizada se comparadas com a RT convencional, embora um acompanhamento prolongado seja necessário para confirmar a possível redução da toxicidade continuada da radiação na RTF em comparação com a RT convencional. Com base na literatura disponível, a RT fracionada convencional e a estereotáxica oferecem tratamento efetivo para a doença de Cushing não controlada isoladamente pela cirurgia. A baixa eficácia e alta toxicidade do tratamento em dose única sugere que a RCU não seja a terapia mais apropriada para a maioria dos pacientes com doença de Cushing.

Intensity modulated radiotherapy in abdominal malignancies: our experience in reducing the dose to normal structures as compared to the gross tumor.

BACKGROUND AND PURPOSE: A better understanding of appropriate sequencing and use of multimodality approach in the management and subsequent improvement in overall survival mandates a vigil on quality of life issues. Intensity modulated radiotherapy (IMRT) is a powerful tool, which might go a long way in reducing radiation doses to critical structures and thereby reduce long term morbidities. The purpose of this paper is to evaluate the impact of IMRT in reducing the dose to the critical normal tissues while maintaining the desired dose to the volume of interest for abdominal malignancies. MATERIALS AND METHODS: During the period January 2002 to March 2004, 11 patients of various sites of malignancies in the abdominal region were treated using physical intensity modulator based IMRT. Plans of these patients treated with IMRT were analyzed using dose volume histograms. RESULTS: An average dose reduction of the mean values by 50% to the liver, 57% to the right kidney, 56% to the left kidney, 66% to the cord and 27% to the bowel, with respect to the GTV could be achieved with IMRT. The two-year disease free survival was 79% and two-year overall survival was 88%. The average number of IMRT fields used was six. CONCLUSION: IMRT with inverse planning enabled us to achieve desired dose distribution, due to its ability to provide sharp dose gradients at the junction of tumor and the adjacent critical organs.

Radioterapia por modulación de intensidad (IMRT): una nueva modalidad en el tratamiento del cáncer de cabeza y cuello / Radiotherapy through intensity modulation (IMRT): a new modality in the treatment of head and neck cancer

Objetivo: Describir el tratamiento y evaluar las ventajas de IMRT en el tratamiento del cáncer de cabeza y cuello. Material y métodos: Hace cuatro años se implementó en el Centro de Cáncer de la Pontificia Universidad Católica la técnica de IMRT para el tratamiento de los tumores de cabeza y cuello. La técnica de IMRT se basa en modificar la intensidad del haz de radiación mediante un colimador multihojas para producir una distribución más exacta de la dosis de radiación. Los resultados se evalúan mediante histogramas dosis/volumen. Se comparan las distribuciones de dosis y toxicidad para radioterapia conformada tridimensional (CRT-3D) e IMRT. Resultados: La distribución de la dosis en los histogramas dosis/volumen demostró una mejor cobertura del volumen blanco (PTV), con IMRT. La dosis recibida por los órganos a riesgo: glándulas salivales, ojos, oídos y cerebro disminuyen con IMRT. La médula espinal se protege con IMRT sin dividir el campo de tratamiento, evitando puntos con menor dosis que podrían disminuir el control del tumor. Conclusiones: La IMRT logra una mejor conformación de la dosis logrando una mejor cobertura del tumor y mayor protección de los órganos a riesgo.

Variations in clinical estimates of tumor volume regression parameters and time factor during external radiotherapy in cancer cervix: does it mimic the linear-quadratic model of cell survival?

BACKGROUND: Tumor regression parameters and time factor during external radiotherapy (EXTRT) are of paramount importance. AIMS: To quantify the parameters of tumor regression and time factor during EXTRT in cancer cervix. SETTINGS AND DESIGN: Patients, treated solely with radiotherapy and enrolled for other prospective studies having weekly tumor regressions recorded were considered. MATERIALS AND METHODS: Seventy-seven patients received 50 Gy of EXTRT followed by intracavitary brachytherapy. Loco-regional regressions were assessed clinically and regression fraction (RF) was represented as RF=c + a 1D + a 2 D2 sub - a 3T, with c, D and T as constant, cumulative EXTRT dose and treatment time respectively. STATISTICAL ANALYSIS USED: Step wise linear regression was performed for RF. Scatter plots were fitted using linear-quadratic fit. RESULTS: Coefficients of parameters D, D2 sub and T were computed for various dose intervals, namely 0--20 Gy, 0--30 Gy, 0--40 Gy and 0--50 Gy. At 0--20 Gy and 0--30 Gy, only the coefficient of D2 was significant (P 2 sub and T turned significant (P 2 sub and T showed significance, leading to an estimate of 26 Gy for a1/a2 and 0.96 Gy/day for a3/a1. CONCLUSIONS: As with alpha/beta and gamma/alpha of post-irradiation cell survival curves, a1/a2 and a3/a1 represents the cumulative effect of various radiobiological factors influencing clinical regression of tumor during the course of EXTRT. The dynamic changes in the coefficients of D, D2 sub and T, indicate their relative importance during various phases of EXTRT.

Planejamento tridimensional para radioterapia de tumores de esôfago: comparação de técnicas de tratamento e análise de probabilidade de complicações / Three-dimensional radiotherapy planning system for esophageal tumors: comparison of treatment techniques and analysis of probability of complications

Para comparar diversas técnicas de irradiação para o câncer de esôfago, foi utilizado sistema de planejamento tridimensional. Em um paciente com carcinoma espinocelular de esôfago médio, foram estudadas as seguintes técnicas de tratamento: dois campos ântero-posteriores e dois campos látero-laterais paralelos e opostos, três campos em "Y" e em "T" e quatro campos em "X". Foram obtidos os histogramas dose-volume, considerando como órgãos de risco medula espinhal e pulmões. Os resultados foram analisados de acordo com as recomendações da Normal Tissue Complication Probability (NTCP) e Tumor Control Probability (TCP). Quanto às doses de irradiação em pulmão, a melhor opção foi a técnica em dois campos ântero-posteriores paralelos e opostos. A medula foi mais poupada quando se utilizaram campos látero-laterais. Sugerimos a combinação de pelo menos duas técnicas de tratamento: ântero-posterior e as técnicas com campos em "Y", "T" ou látero-laterais, para o balanceamento das doses em pulmões e medula espinhal. Ou, ainda, a utilização de técnicas de três campos durante todo o tratamento

Radiotherapy techniques for esophageal cancer were compared using a three-dimensional planning system. We studied the following treatment techniques used for a patient with squamous cell carcinoma of the middle third of the esophagus: two antero-posterior and two latero-lateral parallel opposed fields, three fields ("Y" and "T"), and four fields ("X"). Dose-volume histograms were obtained considering spinal cord and lungs as organs at risk. Analysis was performed comparing doses in these organs as recommended by the Normal Tissue Complication Probability (NTCP) and Tumor Control Probability (TCP). When only the lungs were considered the best technique was two antero-posterior parallel opposed fields. The spinal cord was best protected using latero-lateral fields. We suggest the combination of at least two treatment techniques: antero-posterior fields with "Y" or "T" techniques, or latero-lateral fields in order to balance the doses in the lungs and the spinal cord. Another option may be the use of any of the three-field techniques during the whole treatment.