Unexpected long-term survival after low-dose palliative radiotherapy for nonsmall cell lung cancer

BACKGROUND. Many experienced oncologists have encountered patients with proven nonsmall cell lung cancer (NCLC) who received modest doses of palliative radiotherapy (RT) and who unexpectedly survived for > 5 years; some were apparently cured. We used a very large prospective database to estimate the frequency of this phenomenon and to look for correlative prognostic factors. METHODS. Patients with histologically or cytologically proven NSCLC, treated with palliative RT to a dose of <= 36 Gy, were identified from a prospective database containing details of 3035 new patients registered from 1984-1990. RESULTS. An estimated 1.1% (95% confidence interval, 0.7-1.6%) of 2337 palliative RT patients survived for 5 or more years after commencement of RT, including 18 patients who survived progression -free for 5 years. Estimated median survival was 4.6 months. Five-year survivors had significantly better Eastern Cooperative Oncology Group performance status at presentation than non-5-year survivors (P = 0.024) and were less likely to have distant metastases (P = 0.020). RT dose did not appear to be a significant prognostic factor. Patients who survived 5 years without progression had an estimated 78% probability of remaining free from progression in the next 5years. CONCLUSIONS. Approximately 1% of patients with proven NSCLC survived for > 5 years after palliative RT, and many of these patients appeared to have been cured by a treatment usually considered to be without curative potential. Because of the potential for long-term survival, doses to late-reacting normal tissues should be kept within tolerance when prescribing palliative RT in NSCLC.