Daniels, T.B.

AbstractPurposeTo compare dosimetric performance of volumetric‐modulated arc therapy (VMAT) and small‐spot intensity‐modulated proton therapy for stage III non‐small‐cell lung cancer (NSCLC).Methods and MaterialsA total of 24 NSCLC patients were retrospectively reviewed; 12 patients received intensity‐modulated proton therapy (IMPT) and the remaining 12 received VMAT. Both plans were generated by delivering prescription doses to clinical target volumes (CTV) on averaged 4D‐CTs. The dose‐volume‐histograms (DVH) band method was used to quantify plan robustness. Software was developed to evaluate interplay effects with randomized starting phases of each field per fraction. DVH indices were compared using Wilcoxon rank sum test.ResultsCompared with VMAT, IMPT delivered significantly lower cord Dmax, heart Dmean, and lung V5 Gy[RBE] with comparable CTV dose homogeneity, and protection of other OARs. In terms of plan robustness, the IMPT plans were statistically better than VMAT plans in heart Dmean, but were statistically worse in CTV dose coverage, cord Dmax, lung Dmean, and V5 Gy[RBE]. Other DVH indices were comparable. The IMPT plans still met the standard clinical requirements with interplay effects considered.ConclusionsSmall‐spot IMPT improves cord, heart, and lung sparing compared to VMAT and achieves clinically acceptable plan robustness at least for the patients included in this study with motion amplitude less than 11 mm. Our study supports the usage of IMPT to treat some lung cancer patients.

e16555 Background: The ProtecT trial underscores the importance of treatment in men with prostate cancer and life expectancies > 10 years and the validity of radiation therapy (RT). RT can be given with photons or protons (PT). To address the controversy of which is better, clinical outcomes of photon-based intensity modulated RT (IMRT) and PT cohorts from 2 institutions were directly compared. Methods: Under respective IRB approvals, data from 2 cohorts were analyzed. The first was 301 men treated with ultrasound image guided IMRT from 2000-05 to 75.6 Gy in 42 fractions. The second was 1214 men treated with fiducial image guided PT from 2006-10 to 78 CGE in 39 fractions. Median age and followup were 74 y and 7.2 y for IMRT and 66 y and 5.6 y for PT. Hormone therapy (ADT) was used with IMRT and PT, respectively, in 3% and 7% of low-risk patients, 25% and 9.9% of intermediate-risk, and 91% and 57.8% of high-risk. Comparative endpoints were age-stratified 5-year (5Y) survival (OS), ≥ grade 3 gastrointestinal (GI) and urologic (GU) toxicity, and 5Y freedom from biochemical progression (FFBP). Results: There was a lower prevalence of GI (1.3% vs 0.1%, p = 0.0065) and GU (4.3% vs 0.1%, p < 0.0001) toxicity at last follow-up in the PT group. In the IMRT and PT cohorts, OS rates were 90.8% and 88.7% in men ≥75 (p = 0.4083). In men < 75, OS rates were 91.6% and 97.5% in the IMRT and PT low-risk patients (p = 0.003), 92.1% and 95.5% in the IMRT and PT intermediate-risk (p = 0.0535), and 92.0% and 90.0% (p = 0.4975) in the IMRT and PT high-risk. In the IMRT and PT cohorts, respectively, FFBP rates were 92.2% and 98.9% for low-risk patients (p < 0.0001), 87.3% and 94.5% for intermediate-risk patients(p = 0.0226), and 80.3% and 74.4% for high-risk patients (p = 0.5154). Conclusions: In this retrospective comparison of outcomes in cohorts of men treated with IMRT and PT for prostate cancer, FFBP rates were better with PT for men with low- and intermediate-risk disease and similar in men with high-risk disease despite longer and more frequent use of ADT in the IMRT cohort. This study underscores the difficulty of comparing retrospective series, with differences noted in age, RT dose, and ADT use between cohorts. However, the magnitude of improvement with PT is intriguing and warrants prospective testing.

Small-cell lung cancer (SCLC) has a high predilection for metastasizing to the brain after chemotherapy. This has been blamed on the blood-brain barrier, which prevents chemotherapy from penetrating into the brain, thus creating a sanctuary site. It has been estimated that up to three quarters of patients with SCLC will eventually develop brain metastases. This led investigators to administer prophylactic cranial irradiation (PCI) to decrease this risk. Several trials were performed in patients with SCLC after initial therapy (chemotherapy with or without thoracic radiotherapy) that compared the outcomes of PCI versus no PCI. Early trials generally found that PCI significantly decreased the risk of brain metastases but did not significantly improve survival. These trials were re-evaluated in two larger meta-analyses that included patients with either limited-stage SCLC or extensive-stage SCLC (ESCLC). Both meta-analyses reported that PCI significantly decreased brain metastases and improved survival in patients who had a complete response following initial therapy. These studies were performed before the advent of modern imaging with computed tomography or magnetic resonance imaging (MRI). There have been two modern trials of PCI versus no PCI in patients with ESCLC and both found that PCI decreases brain metastases. The first did not include brain MRI before registration and found that PCI improved survival, whereas the second study did include MRI before registration and at frequent intervals thereafter. That trial found that PCI did not confer a survival advantage. This review will examine the evidence and provide recommendations regarding the role of PCI for patients with ESCLC.

Odontogenic ghost cell carcinoma (OGCC) is a rare and aggressive tumor wherein optimal treatment remains uncertain. We report the first pediatric metastatic OGCC case treated with multimodal therapy: surgery, adjuvant chemoradiation, and adjuvant immunotherapy. Adjuvant therapy was utilized due to locally advanced disease with pathologic features indicative of high recurrence risk. This multimodal approach was modeled after management of primary head and neck cancer, where adjuvant chemoradiation and immunotherapy are associated with improved outcomes. Our patient is alive and disease free at 14 months indicating a potentially positive role for multimodal therapy in the management of OGCC.