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Le de´veloppement de l'irradiation fractionne´e en conditions ste´re´otaxiques a e´te´ permis par la mise au point de syste`mes de contention et de repe´rage 3D non invasifs. Les performances de ces syste`mes ont e´te´ teste´es, et la pre´cision de repositionnement moyenne e´value´e a` ± 1 mm. La pre´cision ge´ome´trique moyenne de l'irradiation e´tant de ± 1 mm, une marge de 2 mm entre le clinical target volume (CTV) et le planning target volume (PTV) est habituellement pre´conise´e. Les proce´dures de contro^le de qualite´ doivent pouvoir assurer la pre´cision requise tout en e´tant compatibles avec le de´roulement des traitements classiques. Diffe´rente sur le plan radiobiologique des traitements non fractionne´s, l'irradiation fractionne´e ste´re´otaxique comple`te la gamme des techniques radiothe´rapiques applicables aux divers processus expansifs intracra^niens.

After exposure to ionizing radiation, eukaryotic cells undergo a G2 delay which contributes to the ability of cells to survive irradiation. For some radioresistant cell lines, this delay is prolonged. Entry of cells into mitosis is regulated by a complex of two proteins cyclin B, and the serine-threonine p34cdc2kinase. When this complex is activated, it undergoes a transport from cytoplasm into the nucleus and phosphorylates proteins which lead to mitosis. P34cdc2kinase is activated by binding to cyclin B and by phosphorylation/dephosphorylation of p34cdc2. Since G2delay after irradiation has been correlated with a rapid inhibition of p34cdc2activity and an enhanced tyrosine phosphorylation, we hypothesized that radioresistant tumors could have a lack in regulation of p34cdc2kinase activity. In this study, we entered 32 patients treated, from 1983 through 1989 at the Claudius Regaud Center, for head and neck squamous cell carcinoma by surgery and standard post-operative doses of radiotherapy. The paraffin embedded tumor specimens had been sampled before radiotherapy for long term controlled patients (n=7) and before and after radiotherapy for patients who had developed a recurrence in the irradiation fields (n=25). Immunohistochemical staining was performed with monoclonal antibodies against p34cdc2(sc-54) and cyclin B (sc-245). A semi-quantitative score was used. For p34cdc2analysis, no difference in intensity of staining was observed between long term controlled patients and those who recurred or, when there was a recurrence before and after radiotherapy. However, there was a highly significant difference (P<0.001) in p34cdc2cell localization with a preferential cytoplasmic localization only for the patients who have a recurrence in the radiotherapy fields. This cytoplasmic localization was present in the primary tumor before radiotherapy and in the recurrence, too. No preferential localization was observed in long term controlled patients. For cyclin B, no difference in intensity of staining was observed anywhere and conversely to p34cdc2, no difference in localization appeared in long term controlled patients nor for patients who have had a recurrence. No correlation existed between localization of p34cdc2and those of cyelin B in patients who recurred. Our results suggest a probably intrinsic abnormality of p34cdc2activity and a lack of association between eyelin B and p34cdc2in head and neck radioresistant squamous cell carcinoma.

Interstitial pneumonitis (IP) is a major toxicity problem after Total Body Irradiation (TBI). The aim of this retrospective study was to evaluate the irradiated lung volumes (ILV) despite shielded blocks to try to correlate the effective ILV with IP incidence. From 1984 to 1994, 146 patients with acute leukemia (AML or ALL) or chronic myeloid leukemia, received TBI prior to Bone Marrow Transplantation (120 Allo, 26 Auto). The IP incidence was 27% in Allo group and 6% in the Auto group. Two groups were comprised: “IP” group (n=35) versus “non-IP” group (n=111). The median follow-up was 32 months. It was given a fractionated TBI (12 Gy/3 fractions/3 days) with customized shielded lung blocks in order to reduce the pulmonary dose to 8 Gy. To calculate the ILV, we used an original digitized image processing with 3D mathematical model applied from the portal films. For every patient, each daily portal film was digitized with 3CCD-camera and improved with image processing. ILV and protected lung volumes were determined from the digitized portal films. The 3D calculations was automatically computed from their measurements to calculate the ILV. The median ILV in both groups was 466cm3. In the “IP” group, the ILV was 484cm3versus 407cm3in the “non-IP” group (P=NS). The median dose-rate was similar between the two groups (0.045Gy/mn).Although the difference was not significant, ours findings suggest a higher incidence of IP when the ILV increased. This hypothesis needs to be confinued by a prospective study.