Method for determining a chemotherapeutic regimen to treat a tumor in a patient, comprising: (a) dewaxing a fixed tumor sample embedded in paraffin to obtain a deparaffinized tumor sample； (b) isolating mRNA from the dewaxed tumor sample in the presence of an effective amount of a chaotropic agent by heating the tissue sample in a solution comprising an effective concentration of a chaotropic compound to a temperature in the range of 75 to 100 ° C. over a period of 5 to 120 minutes and recover the mRNA from the chaotropic solution, in which the tumor is an esophagocardiac adenocarcinoma or non-small cell lung cancer； (c) subjecting the mRNA to amplification using a pair of oligonucleotide primers that hybridize under conditions of high stringency with a region of the GST-pi gene, to obtain an amplified sample； (d) determine the amount of GST-pi mRNA in the amplified sample； (e) compare the amount of GST-pi mRNA of step (d) with an amount of mRNA of an internal control gene； and (f) choose a platinum-based chemotherapeutic regimen as the chemotherapeutic regimen based on the amount of GST-pi mRNA in the amplified sample and a predetermined threshold level for GST-pi gene expression.Método para determinar un régimen quimioterápico para tratar un tumor en un paciente, que comprende: (a) desparafinar una muestra de tumor fijada embebida en parafina para obtener una muestra de tumor desparafinada； (b) aislar ARNm de la muestra de tumor desparafinada en presencia de una cantidad eficaz de un agente caotrópico mediante calentamiento de la muestra de tejido en una disolución que comprende una concentración eficaz de un compuesto caotrópico hasta una temperatura en el intervalo de 75 a 100ºC durante un periodo de tiempo de 5 a 120 minutos y recuperar el ARNm de la disolución caotrópica, en el que el tumor es un adenocarcinoma esofagocardiaco o cáncer de pulmón de células no pequeñas； (c) someter el ARNm a amplificación usando un par de cebadores de oligonucleótido que hibrid
