It has been shown that 252Cf neutron brachytherapy of hemispheric malignant glioma can be readily carried out and may be combined with external, whole brain photon beam therapy of 6,000 rad (60 Gy) administered over a five-week to seven-week period. The ten patients who were studied tolerated both procedures well. There was improvement in performance status, and a decrease in tumor size was observed upon computed tomographic scanning.

Fast-neutron-beam therapy and low-dose-rate fast-neutron intracavitary therapy of cervical carcinoma are effective in producing regression of advanced tumors. However, effectiveness is critically dependent on the schedule by which they are used in combination with fractionated external low-linear-energy-transfer (LET) therapy. Neutron-beam therapy is now alternated frequently with fractionated external radiotherapy (mixed beam). Intracavitary neutron therapy, scheduled before fractionated external-beam photon therapy, was maximally effective. These findings indicate that traditional concepts developed for the use of conventional low-LET therapy may need to be altered to use neutrons for therapy and to achieve improved local control of advanced cancers.

The inclusion of air-filled spaces in treatment fields creates a potential dosimetric problem due to the loss of charged particle equilibrium near the air-tissue interface. We have used a simulated larynx phantom and a small buildup/extrapolation chamber to compare the magnitude and spatial extent of underdosing and overdosing at the distal surface for two linear accelerators (10- and 6-MV x-rays) and a cobalt-60 machine. Surface doses were compared to doses measured in a similar but homogeneous phantom to give observed/expected ratios (O/E), which were greater than 1.0 for large field sizes and less than 1.0 for small field sizes on all machines. The minimum field sizes which produce no surface underdosing for a simulated 2-cm-diam larynx are roughly 7 X 7 cm for 10-MV x-rays, 6 X 6 cm for 6-MV x-rays, and 5 X 5 cm for cobalt-60. In addition, the depth over which underdosing occurs is seen to increase with increasing energy.

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The ability of a [111In]bleomycin complex [( 111In]BLMC) to kill five cell lines of human lung cancer (small cell lung cancer) was investigated. Cells were exposed to either 0.9% NaCl, [111In]Cl3, BLM, [111In]BLMC, nonradioactive InCl3, or In-BLMC for 60 minutes, plated in soft agarose, and assessed for colony formation. [111In]BLMC (40-200 microCi carried by 15-25 micrograms BLM/ml) was more cytotoxic than BLM (15-25 micrograms BLM/ml) by a factor of 1.6-5.3 for five cell lines. The percent survival of N417 cells was 28.4 for [111In]BLMC (40 microCi/15 micrograms BLM/ml) and 54.3 for BLM (15 micrograms/ml); 1.9 for [111In]BLMC (200 microCi/25 micrograms BLM/ml), and 10.0 for BLM (25 micrograms/ml). 111InCl3 (200 microCi/ml) and nonradioactive InCl3 failed to inhibit colony formation. The new [111In]BLMC may be useful for therapy of some lung cancer patients.