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[Microcinematographic study of the lengthening of the cell cycle after x-ray and fast neutron irradiation].

The median cycle duration of unirradiated EMT6 cells is equal to 9.68 +/- 0.20 h. It reaches 10.77 +/- 0.42 h, 12.95 +/- 0.62 h, 14.95 +/- 1.10 h, 16.15 +/- 1.87 h and 20.25 +/- 2.25 h after 250 kV X-rays doses of 1 Gy, 2 Gy, 4 Gy, 6 Gy and 8 Gy respectively and 11.23 +/- 1.03 h, 13.40 +/- 0.53 h and 15.13 +/- 1.15 h after p(65) + Be neutron doses of 0.75 Gy, 1.5 Gy and 2.5 Gy respectively. The corresponding mitotic delay (Tc irradiated - Tc controls) may be evaluated equal to congruent to 1.15 h per Gy for X-rays and to congruent to 2.30 h per Gy for neutrons.

Animals↗

Fast neutrons in the treatment of grade IV astrocytomas.

In 1981, the Hôpital Tenon group and the Orléans neutron therapy team initiated a collaborative study for the treatment of grade IV astrocytomas using a combination of photons and neutrons. Neutrons were used as boost in a reduced volume. Doses were progressively increased from 6 to 7 Gy and later up to 8 Gy. Since October 1994, a neutron boost of 7.5 Gy has been delivered. At the time of evaluation, 294 patients had a minimum follow-up of 12 months. Univariate analysis indicated that clinical status, tumor location and photon fractionation scheme had no significant influence on survival. In contrast, age, surgical procedure and neutron dose were found to be prognostic factors. In a multivariate analysis, the prognostic value of the surgical procedure disappeared and the only remaining independent prognostic factors up to 11 months after treatment (P = 0.001) were age and the neutron dose. As far as neutron dose was concerned, survival increased with dose from 6 to 7 Gy up to 15 months. However, after 15 months, there was no longer any benefit in survival for the patients treated with 8 Gy, and complications related to overdosage began to appear. There was a long-term survival group: 55 patients were alive 18 months after treatment (18%). The median survival was 26.7 months. The best survival was observed for patients treated with a neutron boost of 7 Gy in eight fractions over 11 days (25 vs 18%). The present study demonstrates the feasibility of a combination of photons (30 Gy total brain) followed by a neutron boost (7 Gy) in the treatment of high-grade astrocytomas. The results are in good agreement with the published data. In the literature, age and surgical procedure are currently considered as the most important prognostic factors. The prevalence of neutron dose over these two other prognostic factors, as shown in this study, is an important additional argument in favor of the use of neutrontherapy in the management of these tumors. A possible benefit when combining external fast neutrontherapy with boron neutron capture therapy (BNCT) could reasonably be expected.

Astrocytoma↗