The present invention relates to a pharmaceutical composition comprising 4-phenylbutyric acid derivatives according to the independent claims and further comprising an opioid of the methadone group for use in the treatment of cancer.本發明有關於一種依據獨立項的包含有4-苯丁酸衍生物的藥學組成物並且進一步包含有美沙酮族群的一類鴉片,供用於癌症的治療。