Selective tumor irradiation by infusional brachytherapy in nonresectable pancreatic cancer: a phase I study.

Purpose: Selective high-dose radiation of solid tumors has been a goal of radiation oncology. The physiological barriers of solid tumors (high interstitial tumor pressure, reduced tumor vascularity, and poor perfusion) have been major barriers in achieving significant tumor dose of systemically infused radioconjugates. Direct tumor infusional brachytherapy overcomes these barriers and leads to selective high tumor doses.

Methods And Materials: The development of interstitial tumor infusion of macroaggregated albumin (MAA) followed by colloidal chromic phosphate 32P has overcome solid tumor obstacles in 47 patients with nonresectable pancreatic cancer in a Phase I dose escalation study. The colloidal 32P infusion was followed by external radiation and five fluorouracil.

Results: Of the 28 patients with cancer limited to the pancreas, 15 of 16 patients retained 86-100% (mean 96%) of the infused colloidal 32P isotope. While the other 12 patients had partial shunting to the liver, shunting to the liver was due to high interstitial resistance with tumor dose deposition of 17-88% (mean 52 %). Of the 19 patients with metastatic pancreas cancer, colloidal 32P tumor deposition ranged from 22 to 100% of the infused dose (mean 79%). The less than optimal tumor deposition led to our increasing the MAA from 600,000 to 1.5-2.5 million particles. Interstitial dexamethasone 2 mg and later 4 mg was infused first and prevented liver shunting by somehow reducing tumor resistance. The median survival in 28 Phase I patients with nonresectable pancreas cancer without metastasis, was 12 months. No significant toxicity occurred when treatment was limited to two infusions with as much as 30 mCi each. The maximum tumor dose was 17,000 Gy (1.700,000 cGy). In 19 nonresectable pancreatic cancer patients with metastasis, a 6.9 months median survival was observed.

Conclusions: Infusional brachytherapy is an outpatient procedure that delivers high-dose radiation selectively to pancreatic cancer. Results of the Phase I study in nonresectable pancreas cancer has led to a national multiinstitutional Phase II trial.