Heroin prolongs survival time and retards tumor growth in mice with neuroblastoma

The effect of heroin on tumor growth and survival time was studied in mice with neuroblastoma. Daily SC injections of either 3, 6, 10, or 15 mg/kg heroin were initiated either 2 weeks prior to tumor cell inoculations (pre-treated groups) of 10⁶ S20Y cells or one week after tumor transplantation (post-treated groups); control animals received saline injections prior to tumor cell inoculation (saline-tumor group). Heroin administration that began prior to tumor cell inoculation was effective in inhibiting tumor growth and prolonging life-span at all dosages utilized, but a dose-related response was not observed. A prolongation in mean survival time of 32-39% and median survival time of 8-50% was found in tumor-bearing animals of the pre-treated groups in comparison to mice in the saline-tumor group. Tumor growth was retarded in mice pre-treated with heroin, but mean tumor size of these animals was comparable to controls on the day of death. Only one post-treated group, 6 mg/kg, was observed to have alterations in tumor growth and survival time. Heroin's action in retarding tumor growth and prolonging life-span was blocked by concomitant administration of an opiate antagonist (naloxone, 10 mg/kg). These results suggest that, in addition to heroin's analgesic and behavioral properties, this opiate may have an even greater biologic significance by modulating neoplasia.