Patterns of Locoregional Failure After Exclusive IMRT for Oropharyngeal Carcinoma

Department of Radiation Oncology, University of Texas Medical Branch, Galveston, TX, USA.
International journal of radiation oncology, biology, physics (Impact Factor: 4.26). 05/2008; 72(3):737-46. DOI: 10.1016/j.ijrobp.2008.01.027
Source: PubMed


To assess the patterns of failure after intensity-modulated radiotherapy (IMRT) for oropharyngeal squamous cell carcinoma (SCC).
We analyzed patients treated at the University of Texas Medical Branch between May 2002 and February 2006 who met the following criteria: (1) definitive IMRT without chemotherapy for oropharyngeal SCC; (2) no pretreatment radical surgery; (3) minimal follow-up of 1 year. The location of each nodal/primary failure was co-registered to the pretreatment planning computed tomography scan and then expanded by 5 mm to a planning target volume (PTV) of the failure (PTV-f). We then investigated whether the prescription dose to the PTV-f had been appropriate for the amount of disease present before treatment and whether the PTV-f had been adequately covered.
A total of 50 patients were eligible. With a median follow-up of 32.6 months (range, 12.1-58.6), three local and six regional failures were observed in 8 patients. All but one failure, that had been neglected, were recorded within 14 months of the treatment end. Of the nine failures, four developed in the neck treated electively to the lowest dose level; in all of them, we could retrospectively identify initial positive lymph nodes that might have justified the subsequent failure. The remaining five failures developed in proximity of the high-dose volume. In all but one, the volume of region of interest receiving >/=95% of the dose of the PTV-f was >95%, suggesting adequate coverage. In 1 patient, about 20% of PTV-f was outside the 95% isodose, so that marginal underdosing could not be ruled out.
A potential cause could be identified in all the failures in the lowest dose level. The implications and possible remedies are discussed. Most failures around the high-dose region were "true failures" with no apparent technical cause.

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    • "100 Oropharynx T1–T4 N0–N3 St: III–IVB IMRT Def Yes 42 mths 95.1% (3yrs) 85.3% (3yrs) 92.1% (3yrs) 149 Oropharynx T1–T4 N0–N3 St: III–IVB 2-3DRT Def Yes 42 mths 84.4% (3yrs) 69.3% (3yrs) 75.2% (3yrs) Sanguineti et al. [31] 50 Oropharynx Tx, T1–T4 N0–N3 IMRT Def No 32.6 mths (12.1–58.6 mths) 85% (3yrs) 94% (3yrs) De Arruda et al. [32] 50 Oropharynx T1–T4 N0–N3 St: I–IV IMRT Def: 96% Post: 4% Yes (86%) 18 mths (8.4–76 mths) 88% (2yrs) 98% (2yrs) 84% (2yrs) 98% (2yrs) "
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