Importance of radiation dose in achieving improved loco-regional tumor control in limited stage small-cell lung carcinoma: an update.

Between 1974 and 1986, 576 patients (284 limited and 292 extensive stages) were treated at this institution. To keep multiagent chemotherapy (CT) at a uniform intensity, patients who received (a) combined modality approach of both multiagent chemotherapy and thoracic radiotherapy (RT) and (b) greater than or equal to 3 cycles of multiagent chemotherapy (greater than or equal to 3 drugs), were chosen for this analysis. Out of 284 patients with limited Stage small-cell lung carcinoma, there were 154 such patients who met these strict criteria, and the treatment methods for the remaining 130 patients were as follows: (a) chemotherapy alone with radiotherapy reserved for local failure (47 pts); (b) radiotherapy alone (20 pts); (c) surgery +/- adjuvant chemotherapy or radiotherapy (37 pts); (d) modified chemotherapy plus radiotherapy (26 pts). During the 12-year period, the therapeutic factors have evolved. Radiation-dose was increased from 30-40 Gy (time dose fractionation 49-66) in 1974-1977 to 44-52 Gy (time dose fractionation 73-86) in 1978-1986. The target volume for radiotherapy included the primary lesion with a 2-cm margin of normal lung and the mediastinum. Chemotherapy program also evolved from COP, CAV (1974-1977) to MACC, VCE-VCA, PCE-ACE (1978-1986). Fifty of 154 patients (32%) developed loco-regional recurrence (infield failure) and 98% (49/50) of these patients exhibited this by 2.5 years. Survival data of 154 patients were as follows: (a) Median survival time (MST) was 12 M; (b) actuarial survival rates at 2 and 5 years were 21% and 8%, respectively. Fifty percent of these patients died within 12 months (MST 12 M) and were not exposed to the full length of the risk period for loco-regional failure. To take into account the duration of exposure to the risk period, actuarial method was employed to measure the probability of loco-regional failure. Loco-regional failure rates at 2.5 years were 37%, 39%, 49%, 79%, and 84% for 50 Gy, 45 Gy, 40 Gy, 35 Gy, and 30 Gy, respectively. The difference between the recurrence rates of 37% and 79% by 50 Gy and 35 Gy was statistically significant, p less than 0.05. Although the recurrence rates of 37% and 49% by 50 Gy and 40 Gy were not statistically different, there was a strong trend of a better control rate of loco-regional carcinoma by higher radiation doses. The time to recurrence seems also shorter with lower radiation-dose than that of higher radiation doses.(ABSTRACT TRUNCATED AT 400 WORDS)