Radiotherapy with 6-megavolt photons for early glottic carcinoma: potential impact of extension to the posterior vocal cord.

PURPOSE: Radiation therapy has a high success rate in the treatment of early glottic carcinoma. Excellent outcomes have been reported from centers using cobalt-60 or relatively low-energy (< or = 4 MV) radiation therapy to achieve these results. Whether similar outcomes can be achieved with a 6 MV linear accelerator has been less rigorously evaluated. This study assesses the efficacy of 6 MV radiation therapy for early stage glottic cancer and identifies prognostic factors for local control and overall survival in this common disease. MATERIALS AND METHODS: One hundred twenty-eight consecutive cases of Tis, T1, and T2 squamous cell carcinomas of the glottis from 1982 to 1996 were retrospectively analyzed with regard to local control and survival. All patients were treated with definitive radiation therapy with a 6-MV linear accelerator. Potential prognostic factors for local control and survival were evaluated with univariate and multivariate models. Median follow-up of locally controlled patients was 65 months. RESULTS: The overall 3-year actuarial local control rates for T1 and T2 carcinomas were 86% and 68%, respectively. Patients with lesions involving the posterior third of the vocal cord had significantly worse 3-year local control (76% vs. 86%, P =.038). Radiation therapy technique and overall treatment time did not significantly affect local control. For patients with Tis and T1 lesions, factors associated with significantly worse local control included cordectomy-ineligible disease (P =.024), dose less than 6,600 cGy (P =.024), and lesions limited to the posterior third of the vocal cord (P =.004). Three-year local control was 76%, with doses less than 6,600 cGy and 90% with higher doses. High rates of second primary malignancies were observed and represented the major cause of death. Five-year overall survival was 84%. CONCLUSIONS: The use of 6-MV photons for treatment of early glottic cancer seems to achieve local control similar to that reported with lower-energy photons. However, patients with posterior third involvement had a poorer local control rate with standard radiation therapy, thereby suggesting that alternative approaches be considered.

Factors predicting severe radiation pneumonitis in patients receiving definitive chemoradiation for lung cancer.

PURPOSE: To identify factors that may predict for severe radiation pneumonitis or pneumonopathy (RP), we reviewed a set of simple, commonly available characteristics. METHODS AND MATERIALS: Medical records of 148 lung cancer patients with good performance status (ECOG 0-1) treated definitively with chemoradiation from 6/92-6/98 at the University of Pennsylvania were reviewed. Actuarial survival and the crude rate of severe radiation pneumonitis were determined as a function of several variables. Potential predictive factors examined included age, gender, histology, stage, pulmonary function, performance status (0 vs. 1), weight loss, tumor location, radiation dose, initial radiation field size, chemotherapy regimen, and timing of chemotherapy. Univariate analysis (log-rank test) was performed for each variable. Multivariate analysis was performed using linear regression. RESULTS: Median survival for the entire cohort was 14.7 months. Four patients were inevaluable for pneumonitis due to early death from progressive disease. Of the remaining 144 evaluable patients, 12 (8.3%) experienced severe RP. The most significant factor predicting for severe RP was performance status (p < 0.003). The risk of severe RP was 16% for PS-1 patients vs. 2% for PS-0 patients. Women were significantly more likely to develop severe RP than men (p = 0.01). Among 67 patients for whom pre-radiation therapy pulmonary function data were available, forced expiratory volume of the lung in 1 second (FEV(1)) was also significant (p = 0. 03). No patient suffering severe RP had a pretreatment FEV(1) > 2.0 liters. The median radiation dose was 59.2 Gy and median initial radiation field size was 228 cm(2). Neither radiotherapy factor predicted for RP. Other factors studied, including chemotherapy drugs, and schedule, also were not significant predictors of severe RP. CONCLUSIONS: Pretreatment performance status, gender, and FEV(1) are significant predictors of severe radiation pneumonopathy, at least when using conventional radiation fields and doses. Complex radiation dose-volume algorithms that attempt to predict lung complication probabilities should probably incorporate these simply obtained clinical parameters.

Non-small cell lung cancer: prognostic factors in patients treated with surgery and postoperative radiation therapy.

PURPOSE: To determine survival outcomes, to identify adverse prognostic factors for relapse, and to compare American Joint Commission on Cancer (AJCC) staging systems in patients with non-small cell lung cancer (NSCLC) treated with surgery and postoperative radiation therapy. MATERIALS AND METHODS: Between 1980 and 1995, 211 patients with NSCLC underwent surgery and postoperative radiation therapy. Surgery consisted of wedge resection (12.5%), lobectomy (67.8%), or pneumonectomy (19.7%). Pathologic stages (1992 AJCC) included I (n = 22), II (n = 70), IIIA (n = 104), and IIIB (n = 12). Indications for radiation therapy included compromised margins (n = 81) and/or positive mediastinal nodes (n = 55). Prognostic factors were identified by using univariate and multivariate models. RESULTS: Overall 3-year survival for patients with stage I, II, and IIIA cancer was 58.9%, 44.1%, and 43.2%, respectively. Older age (P = .008), male sex (P = .021), large primary tumor (P = .004), and multiple positive mediastinal nodes (P = .046) were associated with worse rates of survival. Actuarial risk of local-regional relapse (36 patients) was 21.4% at 3 years. In a multivariate model, use of wedge resection (P = .001), positive margins (P = .010), and larger pathologic tumor (P = .059) were risk factors for local-regional recurrence. Actuarial rate of distant failure was 55.2% at 3 years. CONCLUSION: Local-regional control can be achieved with surgery and radiation therapy in approximately 80% of patients; however, the rate of distant metastasis remains unacceptably high. Other variables, such as multiple positive nodes, may serve to identify patients at higher risk for relapse and poorer survival. Methods for improving treatment outcomes in these patients should be pursued.

Calculation of the dose in the build-up region for high energy photon beam. Treatment planning when beam spoilers are employed.

Recoil electrons from a polystyrene sheet (beam spoiler) placed in a photon beam were used to modulate the dose in the build-up region. The effects of the beam spoiler on the dosimetry in simple phantoms were studied for both 6 MV and 15 MV photon beams at 100 cm source-to-surface distance (SSD) as a function of (1) the thickness of the spoiler, (2) the spoiler-to-surface distance (SD) and (3) the field size. A radiotherapy treatment planning (RTP) algorithm was used that employs pencil beam dose deposition kernels to evaluate the three-dimensional (3D) dose distribution due to photons and electrons in the build-up region. To determine the energy deposition kernels for the recoil electrons emanating from the spoiler, their energy spectrum needs to be known. Monte Carlo simulations were performed to derive the spectrum of electrons from the beam spoiler. The recoil electron spectrum was found to be nearly independent of field size, SD, and spoiler thickness. The pencil beam energy deposition kernel was calculated for the recoil electrons from the spoiler and inserted in the treatment planning algorithm. The dose calculation algorithm permits merging the photon and recoil electron dose components. In all cases the calculation agrees to within 3% of the measured results.