The effect of the p53 gene on the survival of mouse testicular cells was evaluated by analysis of degenerating and terminal transferase-mediated end labeling (TUNEL)-positive cells and the subsequent production of further differentiated progeny. In p53 null mice, in contrast to wild-type mice, radiation induced negligible levels of degenerating or TUNEL-positive differentiating spermatogonia within 24 h. This was correlated with higher production of differentiated progeny of the differentiating spermatogonia in p53 null mice. Contrary to the differentiating spermatogonia, the stem spermatogonia of p53 null mice produced fewer differentiated progeny after irradiation than did the stem cells of wild-type mice. We conclude that, because the degeneration and TUNEL positivity of the differentiating spermatogonia in mice of different genotypes were correlated with each other and were dependent on p53, this process is indeed apoptosis. In the differentiating spermatogonia, p53-dependent apoptosis accounted for the bulk of the loss of their progeny after irradiation. Furthermore, whereas the differentiating spermatogonia died by apoptosis that was dependent on p53, the stem spermatogonia, which are more radioresistant, did not.

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The treatment results of 84 patients with clinical stage I and II non‐small cell lung cancer (NSCLC) treated with definitive radiation therapy (RT) alone at Gunma University Hospital from 1976 through 1989 were retrospectively analyzed. All patients were treated with 10 MV X‐rays using anteroposterior parallel opposed fields. The total dose ranged from 60 to 80 Gy, except for one patient given 90 Gy with once‐daily standard fractionation. The 2‐and 5‐year survival rates were 74% and 31% for 28 patients with stage I disease, compared with 40% and 19% for 56 patients with stage II, respectively (P < 0.05). Fifty‐three patients with tumors less than 5 cm in diameter had an in‐field progression rate of 14% at 2 years, in comparison with 38% of 31 patients with tumors greater than 5 cm (P < 0.05). The difference of survival rates for these two groups was statistically significant (P < 0.005). Ten patients given a total dose of 80 Gy or over had only 17% local progression at the time of last follow‐up, however, they had not been alive beyond 3 years because they developed pulmonary insufficiency due to severe stenosis of the proximal bronchus. A multivariate analysis indicated primary tumor size as the only significant prognostic factor for survival. In conclusion, the tumor size was the most important factor not only for local control but also for distant failure. It was also suggested that the optimal radiation dose for medically inoperable stage I‐II NSCLC ranged from 60 to 70 Gy with once‐daily standard fractionation. Radiat Oncol Invest 1996;4:165–170. © 1996 Wiley‐Liss, Inc.