Radiotherapy in the treatment of brain metastasis from small cell lung carcinoma. Study on appropriately controlled dose

Fifty-two brain metastatic lesions occurring in 20 patients with small cell lung carcinoma (SCLC) were irradiated, and then the relationship between tumor size, dose and control was clinically and histopathologically studied. Lesions of 8 mm in diameter and those of 10 mm in diameter were determined to be controllable by irradiation at about 38 Gy and 42 Gy, respectively. According to size-dependent curative minimum doses, the lesions could be divided by the 10 Gy/5 fr/wk method into controlled and non-controlled groups with the curve expressed as dose (Gy) =15.27 log10(tumor volume (mm3))+0.6. Based on these results, tumors of 2 mm and 3 mm in diameter were estimated to be controllable at 14 and 20 Gy, respectively. Thus prophylactic cranial irradiation (PCI) in the treatment of SCLC was thought to be not always necessary if early treatment of small metastatic lesions, detected by Gd-DTPA-enhanced MRI could be achieved. The optimal interval between follow-up examinations was thought to be 1 month during the first two years after the diagnosis of SCLC, and then 3 months after that. In addition, the omission of PCI can save many patients who do not actually require PCI from suffering its adverse effects. (author)