Impact of tumor control on survival in carcinoma of the lung treated with irradiation

Abstract

The long-term results in tumor response, intrathoracic tumor control and survival are reported in patients with medically inoperable or unresectable non-oat cell and small cell carcinoma of the lung. In 376 patients with stages T1–3, NO-2 carcinoma of the lung tumors, accessioned to a Radiation Therapy Oncology Group (RTOG) randomized study to evaluate different doses of irradiation, a higher complete response rate (24%), intrathoracic tumor control (67%) and three year survival (15%) was observed with 6000 cGy, compared with lower doses of irradiation (4000 or 5000 cGy). Increased survival was noted in patients with complete tumor response. Three year survival in complete responders was 23%, in partial responders, 10%, and in patients with stable disease, 5%. Patients treated with 6000 cGy had an overall intrathoracic failure rate of 33% at 3 years, compared with 42% for those treated with 5000 cGy, 44% for patients receiving 4000 cGy with split course, and 52% for those treated with 4000 cGy continuous course ( p = 0.02). Patients surviving 6 or 12 months exhibited a statistically significant increased survival when the intrathoracic tumor was controlled. Patients treated with 5000–6000 cGy, showing tumor control, had a three year survival of 22%, versus 10%, if they had intrathoracic failure ( p = 0.05). In patients treated with 4000 cGy (split or continuous), the respective survival was 20% and 10%, if the intrathoracic tumor was controlled ( p = 0.001). In patients surviving 12 months after treatment with 5000–6000 cGy, on whom the intrathoracic tumor was controlled, the median survival was 23 months, in contrast to 12 months, if they developed intrathoracic failure ( p = 0.05). In patients treated with 4000 cGy, the median survival was 17 months with control and 12 months without control of the intrathoracic tumor. ( p = 0.008). In another RTOG study for patients with more advanced tumors (T4 or N3), those with local tumor control at 12 months had a three year survival rate of 25%, compared with 5% for those with thoracic failures. These differences are statistically significant ( p = 0.006). Higher doses of irradiation yield a greater proportion of complete response, higher intrathoracic tumor control and better survival in non-oat cell medically inoperable or unresectable carcinoma of the lung. In a randomized study, the Southeastern Cancer Study Group (SECSG) reported that patients with small cell carcinoma of the lung given thoracic irradiation (4000 cGy in split course) in addition to Cytoxan, Adriamycin, and Vincristine (CAV) for a minimum of 6 cycles plus brain irradiation (3600 cGy, 15 fractions split course) at two years, had a higher intrathoracic tumor control (65%) than patients not given thoracic irradiation (52%). However, at 3 to 4 years, the intrathoracic failure rate was 50% for the patients receiving thoracic irradiation (28% in-field and 17% recurrence outside the radiotherapy field), in contrast to 52% intrathoracic failure without thoracic irradiation. The 2 year survival in the patients receiving thoracic irradiation was 35%, compared to 20% for those not receiving thoracic irradiation. At 3 years, however, the survival is similar in both groups. Among those patients eligible for consolidation (minimum of 6 cycles of chemotherapy without progressive disease), the 3 year survival was 35% for the group receiving thoracic irradiation and 20% for those treated with chemotherapy and brain irradiation alone ( p = 0.04). In both treatment groups, the only long-term survivors were those patients who did not develop chest relapses or distant metastases. All patients who failed in the chest, with or without distant metastases, died within 36 months. Intrathoracic tumor control is clearly associated with improved survival in patients with small cell carcinoma of the lung.