Among patients with limited disease small-cell lung cancer that has responded completely to treatment, preventive radiation therapy to the brain appears to extend survival even after accounting for impact on quality of life. These results were published in the Journal of Clinical Oncology.

Small cell lung cancers (SCLC) account for 20–25% of all lung cancers and are primarily diagnosed in smokers or former smokers. They differ from other types of lung cancer in that they spread very quickly throughout the body via the blood and lymphatic system.

Limited disease SCLC refers to cancer that is confined to a single location in the chest and is not detectable outside the lung. Both chemotherapy and radiation therapy to the chest are commonly used for the treatment of limited disease SCLC.

A common occurrence among patients with SCLC is spread of the cancer to the brain. To reduce the risk of developing brain metastases, patients with limited disease SCLC that has responded completely to treatment may receive radiation therapy to the brain before brain metastases become apparent; this is called prophylactic cranial irradiation. While this practice improves survival, the benefits must be weighed against possible long-term side effects of radiation on the brain.

To help physicians and patients weigh the risks and benefits of prophylactic cranial irradiation, researchers developed a statistical model that included survival estimates and information about the frequency and severity of long-term side effects from prophylactic cranial irradiation. The model is only intended to apply to patients with limited disease SCLC who have no detectable cancer following treatment (a complete treatment response).

Based on current rates of survival and the best available information about long-term radiation side effects, prophylactic cranial irradiation extends survival even after accounting for its impact on quality of life. In general, the model predicts that prophylactic cranial irradiation will improve quality-adjusted survival whenever the frequency of radiation side effects is low, the severity of radiation side effects is mild, or long-term survival is low. As survival improves (as it most likely will as treatment continues to improve), the side effects of radiation have a bigger impact on quality of life, and minimizing these side effects will become more important.

These results suggest that prophylactic cranial irradiation benefits patients with limited-disease SCLC that has responded completely to treatment. As survival with SCLC continues to improve, it will be important to minimize the long-term side effects of prophylactic cranial irradiation in order to continue to see a benefit.

Reference: Lee JJ, Bekele BN, Zhou X, Cantor SB, Komaki R, Lee JS. Decision Analysis for Prophylactic Cranial Irradiation for Patients with Small-cell Lung Cancer. Journal of Clinical Oncology. 2006;24:3597-3603.