Volumetric tumor burden and its effect on brachial plexus dosimetry in head and neck intensity-modulated radiotherapy

Department of Radiation Oncology, Boston Medical Center, Boston University School of Medicine, Boston, MA
Medical dosimetry: official journal of the American Association of Medical Dosimetrists (Impact Factor: 0.76). 01/2014; 39(2). DOI: 10.1016/j.meddos.2013.12.004
Source: PubMed


To determine the effect of gross tumor volume of the primary (GTV-P) and nodal (GTV-N) disease on planned radiation dose to the brachial plexus (BP) in head and neck intensity-modulated radiotherapy (IMRT). Overall, 75 patients underwent definitive IMRT to a median total dose of 69.96Gy in 33 fractions. The right BP and left BP were prospectively contoured as separate organs at risk. The GTV was related to BP dose using the unpaired t-test. Receiver operating characteristics curves were constructed to determine optimized volumetric thresholds of GTV-P and GTV-N corresponding to a maximum BP dose cutoff of > 66Gy. Multivariate analyses were performed to account for factors associated with a higher maximal BP dose. A higher maximum BP dose (> 66 vs ≤ 66Gy) correlated with a greater mean GTV-P (79.5 vs 30.8cc; p = 0.001) and ipsilateral GTV-N (60.6 vs 19.8cc; p = 0.014). When dichotomized by the optimized nodal volume, patients with an ipsilateral GTV-N ≥ 4.9 vs < 4.9cc had a significant difference in maximum BP dose (64.2 vs 59.4Gy; p = 0.001). Multivariate analysis confirmed that an ipsilateral GTV-N ≥ 4.9cc was an independent predictor for the BP to receive a maximal dose of > 66Gy when adjusted individually for BP volume, GTV-P, the use of a low anterior neck field technique, total planned radiation dose, and tumor category. Although both the primary and the nodal tumor volumes affected the BP maximal dose, the ipsilateral nodal tumor volume (GTV-N ≥ 4.9cc) was an independent predictor for high maximal BP dose constraints in head and neck IMRT.

1 Follower
19 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A representation and interpretation of the area under a receiver operating characteristic (ROC) curve obtained by the "rating" method, or by mathematical predictions based on patient characteristics, is presented. It is shown that in such a setting the area represents the probability that a randomly chosen diseased subject is (correctly) rated or ranked with greater suspicion than a randomly chosen non-diseased subject. Moreover, this probability of a correct ranking is the same quantity that is estimated by the already well-studied nonparametric Wilcoxon statistic. These two relationships are exploited to (a) provide rapid closed-form expressions for the approximate magnitude of the sampling variability, i.e., standard error that one uses to accompany the area under a smoothed ROC curve, (b) guide in determining the size of the sample required to provide a sufficiently reliable estimate of this area, and (c) determine how large sample sizes should be to ensure that one can statistically detect differences in the accuracy of diagnostic techniques.
    Radiology 05/1982; 143(1):29-36. DOI:10.1148/radiology.143.1.7063747 · 6.87 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: With the increasing use of intensity-modulated radiation therapy (IMRT) for the treatment of head and neck cancer, radiation oncologists are expected to have an in-depth knowledge of the computed tomographic (CT) and magnetic resonance (MR) imaging anatomy of this region to be able to accurately characterize tumor extent and define organs at risk for potential radiation injury. The brachial plexus is a complex anatomic structure in the head and neck adjacent to diseased nodes and elective nodal volumes (ie, nodal areas that are prophylactically treated because they are at high risk for micrometastatic disease) and should, therefore, be carefully identified and contoured at CT prior to IMRT planning. A number of multi-institutional protocols mandate contouring the brachial plexus as an "avoidance structure" (ie, a structure or volume that is at risk for complications of radiation therapy) in the planning of head and neck radiation therapy, and, although little information exists on the best method of doing so consistently, contouring may be facilitated with fusion CT-MR imaging software. With three-dimensional conformal radiation therapy, the brachial plexus is not routinely contoured; therefore, its dose limits are not evaluated in treatment planning. In contrast, with IMRT, tolerance doses can be set to limit the maximum dose to the brachial plexus to 60 Gy in most radiation protocols, although the true radiation tolerance dose in patients with head and neck cancer has been mentioned only sporadically in the literature. Additional studies will be required to determine if identification of the brachial plexus as an avoidance structure prior to radiation therapy planning improves treatment outcome in patients with head and neck cancer and reduces long-term toxicity in this structure.
    Radiographics 07/2010; 30(4):1095-103. DOI:10.1148/rg.304095105 · 2.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To compare the prognostic utility of the 2-[(18)F] fluoro-2-deoxy-D: -glucose (FDG) maximum standardized uptake value (SUV(max)), primary gross tumor volume (GTV), and FDG metabolic tumor volume (MTV) for disease control and survival in patients with head and neck squamous cell carcinoma (HNSCC) undergoing intensity-modulated radiotherapy (IMRT). Between 2007 and 2011, 41 HNSCC patients who underwent a staging positron emission tomography with computed tomography and definitive IMRT were identified. Local (LC), nodal (NC), distant (DC), and overall (OC) control, overall survival (OS), and disease-free survival (DFS) were assessed using the Kaplan-Meier product-limit method. With a median follow-up of 24.2 months (range 2.7-56.3 months) local, nodal, and distant recurrences were recorded in 10, 5, and 7 patients, respectively. The median SUV(max), GTV, and MTV were 15.8, 22.2 cc, and 7.2 cc, respectively. SUV(max) did not correlate with LC (p = 0.229) and OS (p = 0.661) when analyzed by median threshold. Patients with smaller GTVs (<22.2 cc) demonstrated improved 2-year actuarial LC rates of 100 versus 56.4 % (p = 0.001) and OS rates of 94.4 versus 65.9 % (p = 0.045). Similarly, a smaller MTV (<7.2 cc) correlated with improved 2-year actuarial LC rates of 100 versus 54.2 % (p < 0.001) and OS rates of 94.7 versus 64.2 % (p = 0.04). Smaller GTV and MTV correlated with improved NC, DC, OC, and DFS, as well. GTV and MTV demonstrate superior prognostic utility as compared to SUV(max), with larger tumor volumes correlating with inferior local control and overall survival in HNSCC patients treated with definitive IMRT.
    Annals of Nuclear Medicine 05/2012; 26(7):527-34. DOI:10.1007/s12149-012-0604-5 · 1.68 Impact Factor
Show more