Abstracts Neutron vs Photon Irradiation of Inoperable Salivary

Gland Tumors: Results of an RTOG-MRC Cooper- ative Randomized Study. TW Griffin, TF Pajak, GE Laramore, et al. Int J Radiat Oncol Biol Phys 1988; 15:1085-1090

This paper reports the results of a prospective ran- domized study comparing fast neutron radiation ther- apy with conventional photon and electron therapy for malignant salivary gland tumors. A total of 32 pa- tients with inoperable, recurrent, or unresectable tu- mors were entered into the study. Seventeen patients were randomized to receive neutron therapy and 15 patients were randomized to receive photons. The minimum follow-up time was 2 years, with 25 pa- tients eligible for follow-up analysis of data. It was found that complete tumor clearance rate at the pri- mary site was 85% for neutrons and 33% for photons, a statistically significant difference. The complete tu- mor clearance rate at the cervical lymph nodes was 86% for neutrons and 25% for photons. At 2 years, the local and regional control rates for the two groups were 67% for neutrons and 17% for photons. When absolute survival rates were examined, however, there was a trend favoring neutrons, but a statistically sig- nificant level was not achieved. A similar trend to- ward higher toxicity in the neutron-treated patients was also noted. Neutron therapy offers several poten- tial advantages over conventional photon or electron radiation. These advantages are related to increased energy delivery from neutrons compared with pho- tons or electrons. Neutron therapy thereby results in a reduced cellular ability to repair sublethal radiation damage, less variation in radio-sensitivity across the cell cycle, and an increase in the ability to kill hypoxic cells.

Although the sample size was small, this study is one of the few reported randomized prospective stud- ies that support the contention that fast neutron radio- therapy offers a significant advance in the treatment of inoperable and unresectable primary and recurrent malignant salivary gland tumors. Whether this modal- ity will prove useful in the future for the primary treat- ment of such lesions needs to be determined. It should be noted that there is a tendency toward a higher in- cidence of complications with neutron beam therapy, and only a few treatment centers are available to de- liver such therapy.

Carcinoma of the Nasal Cavity-Results of Primary and Adjuvant Radiotherapy. RB Hawkins, JH Wyn- stra, MV Pilepich, et al. Int J Radiat Oncol Biol Phys 1988; 15:1129-1133

This is a report documenting the experience with carcinoma of the nasal cavity at the Mallinckrodt In- stitute of Radiology. The most common histologic sub- types seen were epidermal carcinoma, undifferenti- ated carcinoma, and adenoid cystic carcinoma. In 66% of cases there was tumor extension beyond the nose, with the paranasal sinuses being the most commonly

involved extra-nasal site. The orbits were also in- volved in 25% of cases. Overall, roughly 40% of pa- tients presented with stage 1 or 3 disease, with 20% of patients presenting with stage 2 disease. At 5 years, the overall survival rate was 52%. It was found that survival was not significantly affected by tumor his- tology, tumor site, or the nodal status of the patient. Fifty percent of patients failed initial therapy with lo- cal recurrence being the dominant mode of failure. Severe complications of radiotherapy occurred in 9% of patients with epidermal carcinoma. These compli- cations included recurrent epistaxis, otitis media, and soft tissue necrosis with fistulization. Of six patients with adenoid cystic carcinoma of the nasal cavity, two developed severe complications including late optic neuropathy and death due to biopsy-proven brain ne- crosis. This study did not stratify patients treated with wide local incision v enbloc resection of the paranasal sinuses involved with tumor. In addition, contrary to clinical experience, survival was not significantly af- fected by tumor site (for example, nasal septum v na- sal vestibule), nor was survival affected by nodal sta- tus. However, this article does point out that regional failure continues to be a major problem with treatment of this tumor. These data do suggest, albeit indirectly, that combined surgery plus radiation may prove to be the best treatment modality for nasal carcinoma.

A Novel Cancer Therapy Using a Mossbauer-Isotope Compound. RL Mills, CW Walter, L Venkataraman, et al. Nature 1988; 336:787-789

Radiotherapy for cancer treatment uses a high dos- age of ionizing radiation because only a small fraction of the absorbed dose leads to lethal double-strand breaks in tumor cell DNA. More efficient breaks in DNA would be produced by high-energy electrons generated in proximity to the DNA. In addition, if the energy of these electrons can be dispersed within a short distance of the tumor cell, then a single event would be lethal to the cell, sparing the neighboring normal cells and as much soft tissue as possible. This report is an exciting preliminary study examining the feasibility of administering radiation in a manner se- lective for tumor cell DNA with rapid dispersion of energy, sparing normal tissue. The investigators mea- sured the magnitude of enhanced cell killing using 57Fe [III) bleomycin administered to malignant cells in vitro and in vivo and radiated with gamma rays. Bleo- mycin was used because it strongly binds to DNA by inserting between base pairs, thereby focusing the en- ergy of the administered gamma rays. When this form of treatment was given to cell lines derived from hu- man breast cancer, it significantly decreased cell pro- liferation relative to control cells. In addition, when mice bearing spontaneous mammary adenocarcino- mas were treated in this fashion, there was a signifi- cant reduction in tumor volume. There were negligi- ble radiation doses and pharmacologic toxicity to the surrounding cells. This is a preliminary experimental report that has important implications for future ther-

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