Response of pancreatic cancer to local irradiation with high-energy neutrons

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Abstract
Seventy-seven patients with locally advanced, nonresectable, biopsy-proven adenocarcinoma of the pancreas were treated by palliative bypass surgery followed by intensive neutron beam irradiation of the primary tumor site. Three dose levels, under 20, 21 to 23, and 24 to 25 Gy, were studied with the use of a treatment plan that included all known disease within a limited target volume, generally under 21. Symptomatic palliation was achieved in the majority of patients. The median survival time was 6 months. One patient remained alive and well without evidence of tumor 5 years after irradiation. Two were free of tumor at autopsy (one had died of intercurrent disease and one of radiation-related complications). A common cause of death was metastatic dissemination. Complication rates were dosedependent; life-threatening complications did not exceed 12% with doses of less than 23 Gy. Autopsies from 19 patients were reviewed. In all, the pancreatic tumor site showed extensive reactive fibrosis. Local control was achieved in two patients, but most had both residual tumor in the pancreas and metastases. Six patients had centrolobular veno-occlusive liver disease. These patients had all received the higher (22–24 Gy) neutron doses. Six patients had hemorrhagic radiation gastroenteritis. Mild skin atrophy and bone marrow hypoplasia were seen in the irradiated volumes. The kidneys and spinal cord showed no radiation effects. The authors conclude that neutron irradiation can provide a good local response with marked regression and fibrosis of the tumor. This response, coupled with many deaths due to metastases, suggests that combined treatment with neutrons and chemotherapy would be worth exploring.