Radiation-Induced Secondary Cancer Risk Assessment in Patients With Lung Cancer After Stereotactic Body Radiotherapy Using the CyberKnife M6 System With Lung-Optimized Treatment

Hypofractionated stereotactic radiotherapy (HypoFXSRT) has recently been used for the treatment of small lung tumors. We retrospectively analyzed the treatment outcome of HypoFXSRT for stage I non-small cell lung cancer (NSCLC) treated in a Japanese multi-institutional study. This is a retrospective study to review 257 patients with stage I NSCLC (median age, 74 years: 164 T1N0M0, 93 T2N0M0) were treated with HypoFXSRT alone at 14 institutions. Stereotactic three-dimensional treatment was performed using noncoplanar dynamic arcs or multiple static ports. A total dose of 18 to 75 Gy at the isocenter was administered in one to 22 fractions. The median calculated biological effective dose (BED) was 111 Gy (range, 57-180 Gy) based on alpha/beta = 10. During follow-up (median, 38 months), pulmonary complications of above grade 2 arose in 14 patients (5.4%). Local progression occurred in 36 patients (14.0%), and the local recurrence rate was 8.4% for a BED of 100 Gy or more compared with 42.9% for less than 100 Gy (p < 0.001). The 5-year overall survival rate of medically operable patients was 70.8% among those treated with a BED of 100 Gy or more compared with 30.2% among those treated with less than 100 Gy (p < 0.05). Although this is a retrospective study, HypoFXSRT with a BED of less than 180 Gy was almost safe for stage I NSCLC, and the local control and overall survival rates in 5 years with a BED of 100 Gy or more were superior to the reported results for conventional radiotherapy. For all treatment methods and schedules, the local control and survival rates were better with a BED of 100 Gy or more compared with less than 100 Gy. HypoFXSRT is feasible for curative treatment of patients with stage I NSCLC.

To evaluate the clinical outcomes of 48 Gy of three-dimensional stereotactic radiotherapy in four fractions for treating Stage I lung cancer using a stereotactic body frame. Forty-five patients who were treated between September 1998 and February 2004 were included in this study. Thirty-two patients had Stage IA lung cancer, and the other 13 had Stage IB lung cancer where tumor size was less than 4 cm in diameter. Three-dimensional treatment planning using 6-10 noncoplanar beams was performed to maintain the target dose homogeneity and to decrease the irradiated lung volume >20 Gy. All patients were irradiated using a stereotactic body frame and received four single 12 Gy high doses of radiation at the isocenter over 5-13 (median = 12) days. Seven tumors (16%) completely disappeared after treatment (CR) and 38 tumors (84%) decreased in size by 30% or more (PR). Therefore, all tumors showed local response. During the follow-up of 6-71 (median = 30) months, no pulmonary complications greater than an National Cancer Institute-Common Toxicity Criteria of Grade 3 were noted. No other vascular, cardiac, esophageal, or neurologic toxicities were encountered. Forty-four (98%) of 45 tumors were locally controlled during the follow-up period. However, regional recurrences and distant metastases occurred in 3 and 5 of T1 patients and zero and 4 of T2 patients, respectively. For Stage IA lung cancer, the disease-free survival and overall survival rates after 1 and 3 years were 80% and 72%, and 92% and 83%, respectively, whereas for Stage IB lung cancer, the disease-free survival and overall survival rates were 92% and 71%, and 82% and 72%, respectively. Forty-eight Gy of 3D stereotactic radiotherapy in 4 fractions using a stereotactic body frame is useful for the treatment of Stage I lung tumors.

We investigated the relation between radiotherapy in childhood for tinea capitis and the later development of tumors of the brain and nervous system among 10,834 patients treated between 1948 and 1960 in Israel. Benign and malignant tumors were identified from the pathology records of all Israeli hospitals and from Israeli national cancer and death registries. Doses of radiation to the neural tissue were retrospectively estimated for each patient (mean, 1.5 Gy). Sixty neural tumors developed in the patients exposed as children, and the 30-year cumulative risk (+/- SE) was 0.8 +/- 0.2 percent. The incidence of tumors was 1.8 per 10,000 persons per year. The estimated relative risk as compared with that for 10,834 matched general-population controls and 5392 siblings who had not been irradiated was 6.9 (95 percent confidence interval, 4.1 to 11.6) for all tumors and 8.4 (confidence interval, 4.8 to 14.8) when the analysis was restricted to neural tumors of the head and neck. Increased risks were apparent for meningiomas (relative risk, 9.5; n = 19), gliomas (relative risk, 2.6; n = 7), nerve-sheath tumors (relative risk, 18.8; n = 25), and other neural tumors (relative risk, 3.4; n = 9). A strong dose--response relation was found, with the relative risk approaching 20 after estimated doses of approximately 2.5 Gy. Our study confirms that radiation doses on the order of 1 to 2 Gy can significantly increase the risk of neural tumors.