K. Miyagi

Dose--volume metrics associated with radiation pneumonitis after stereotactic body radiation therapy for lung cancer.

PURPOSE To identify dose-volume factors associated with radiation pneumonitis (RP) after stereotactic body radiation therapy (SBRT) for lung cancer. METHODS AND MATERIALS This study analyzed 74 patients who underwent SBRT for primary lung cancer. The prescribed dose for SBRT was uniformly 48 Gy in four fractions at the isocenter. RP was graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v.3. Symptomatic RP was defined as grade 2 or worse. Optimal cut-offs dividing the patient population into two subgroups based on the incidence of symptomatic RP were sought using the following dose-volume metrics: PTV volume (ml), mean lung dose (Gy), and V5, V10, V15, V20, V25, V30, V35, and V40 (%) of both lungs excluding the PTV. RESULTS With a median follow-up duration of 31.4 months, symptomatic RP was observed in 15 patients (20.3%), including 1 patient with grade 3. Optimal cut-offs for pulmonary dose-volume metrics were V25 and V20. These two factors were highly correlated with each other, and V25 was more significant. Symptomatic RP was observed in 14.8% of the patients with V25 <4.2%, and the rate was 46.2% in the remainder (p = 0.019). PTV volume was another significant factor. The symptomatic RP rate was significantly lower in the group with PTV <37.7 ml compared with the larger PTV group (11.1% vs. 34.5%, p = 0.020). The patients were divided into three subgroups (patients with PTV <37.7 ml; patients with, PTV ≥37.7 ml and V25 <4.2%; and patients with PTV ≥37.7 ml and V25 ≥4.2%); the incidence of RP grade 2 or worse was 11.1%, 23.5%, and 50.0%, respectively (p = 0.013). CONCLUSIONS Lung V25 and PTV volume were significant factors associated with RP after SBRT.

Patterns of Failure Associated with Involved Field Radiotherapy in Patients with Clinical Stage I Thoracic Esophageal Cancer

OBJECTIVE To analyze the patterns of the first sites of failure in patients with clinical stage I thoracic esophageal cancer after involved field radiotherapy and to determine whether elective nodal irradiation is necessary for these patients. MATERIALS AND METHODS Between 2000 and 2007, 68 patients aged 43-84 years with clinical stage I thoracic esophageal cancer received definitive radiotherapy. The radiation field included the primary tumor with a 3-cm margin in the cranio-caudal direction. Patterns of lymph node failure were classified according to the first sites of failure. In-field, regional and distant lymph node failures were defined as lymph node failures within the irradiated area, within the mediastinum or perigastric area beyond the irradiated area, and outside the regional lymph nodes, respectively. RESULTS The 3 year overall and disease-free survival rates were 76 and 66%, respectively (median follow-up: 42 months). Twenty-two of the 68 patients exhibited treatment failure. Local failure with or without recurrence in other sites was observed in 11 patients, lymph node failure in 10 patients, and distant metastasis in 1. Of the 10 patients with lymph node failure, sites of failure were in-field in 1 patient, in-field and distant in 1, regional in 3, distant in 2 and distant and regional in 3. CONCLUSIONS Involved field radiotherapy did not result in significant incidence of regional lymph node failure in clinical stage I thoracic esophageal cancer patients. However, further investigation is needed to establish the optimal radiotherapy field for clinical stage I thoracic esophageal cancer.

Craniocaudal Safety Margin Calculation Based on Interfractional Changes in Tumor Motion in Lung SBRT Assessed With an EPID in Cine Mode

PURPOSE To evaluate setup error and interfractional changes in tumor motion magnitude using an electric portal imaging device in cine mode (EPID cine) during the course of stereotactic body radiation therapy (SBRT) for non-small-cell lung cancer (NSCLC) and to calculate margins to compensate for these variations. MATERIALS AND METHODS Subjects were 28 patients with Stage I NSCLC who underwent SBRT. Respiratory-correlated four-dimensional computed tomography (4D-CT) at simulation was binned into 10 respiratory phases, which provided average intensity projection CT data sets (AIP). On 4D-CT, peak-to-peak motion of the tumor (M-4DCT) in the craniocaudal direction was assessed and the tumor center (mean tumor position [MTP]) of the AIP (MTP-4DCT) was determined. At treatment, the tumor on cone beam CT was registered to that on AIP for patient setup. During three sessions of irradiation, peak-to-peak motion of the tumor (M-cine) and the mean tumor position (MTP-cine) were obtained using EPID cine and in-house software. Based on changes in tumor motion magnitude (∆M) and patient setup error (∆MTP), defined as differences between M-4DCT and M-cine and between MTP-4DCT and MTP-cine, a margin to compensate for these variations was calculated with Strooms formula. RESULTS The means (±standard deviation: SD) of M-4DCT and M-cine were 3.1 (±3.4) and 4.0 (±3.6) mm, respectively. The means (±SD) of ∆M and ∆MTP were 0.9 (±1.3) and 0.2 (±2.4) mm, respectively. Internal target volume-planning target volume (ITV-PTV) margins to compensate for ∆M, ∆MTP, and both combined were 3.7, 5.2, and 6.4 mm, respectively. CONCLUSION EPID cine is a useful modality for assessing interfractional variations of tumor motion. The ITV-PTV margins to compensate for these variations can be calculated.

Definitive Radiotherapy for T1–2 Hypopharyngeal Cancer: A Single-Institution Experience

PURPOSE To analyze the outcome in T1-2 hypopharyngeal cancer (HPC) patients treated with definitive radiotherapy (RT). PATIENTS AND METHODS A total of 103 patients with T1-2 hypopharyngeal squamous cell carcinoma treated with radical RT between March 2000 and June 2008 at our institution were analyzed. Pre-RT neck dissection (ND) was performed in 26 patients with advanced neck disease. Chemotherapy was used concurrently with RT in 14 patients. Sixty patients were associated with synchronous or metachronous malignancies. The median follow-up for surviving patients was 41 months. RESULTS The 3-year overall and cause-specific survival rates were 70% and 79%, respectively. The 3-year local control rates were 87% for T1 and 83% for T2 disease. The ultimate local control rate was 89%, including 7 patients in whom salvage was successful. The ultimate local control rate with laryngeal preservation was 82%. Tumors of the medial wall of the pyriform sinus tended to have lower control rates compared with tumors of the lateral or posterior pharyngeal wall. Among patients with N2b-3 disease, the 3-year regional control rates were 74% for patients with pre-RT ND and 40% for patients without ND. The 3-year locoregional control rates were as follows: Stage I, 100%; Stage II, 84%; Stage III, 67%; Stage IVA, 43%; Stage IVB, 67%. Forty-two patients developed disease recurrence, with 29 (70%) patients developing recurrence within the first year. Of the 103 patients, 6 developed late complications higher than or equal to Grade 3. CONCLUSIONS Definitive RT accomplished a satisfactory local control rate and contributed to organ preservation.