Familial Nasopharyngeal Carcinoma 6

Selection and Delineation of Target Volumes in Intensity-Modulated Radiation Therapy for Nasopharyngeal Cancer 225Table 17.5. Differences of delineation of CTV between the “recuded-volume” technique and the RTOG protocols“Reduced-volume” technique RTOG-0225 RTOG-0615Sphenoid sinusInferior part (in sphenoid sinusinvolved disease, the entire sphenoidsinus)Inferior partInferior part (in T3 and T4diseases, the entire sphenoidsinus)Ethmoid sinus Posterior Not included Not includedNasal cavityMaxillary sinus5 mm anterior to posterior nasalaperture5 mm anterior to maxillarymucosaPosterior 1/3 Posterior 1/4 to 1/3Posterior 1/3 Posterior 1/4 to 1/3Clivis Anterior 1/3 Entire Anterior 1/2 to 2/3Retropharyngeal nodesFrom base of skull to cranial edgeof the second cervical vertebraFrom base of skull to cranialedge of the hyoidFrom base of skull to cranialedge of the hyoidUpper deep jugular nodes(retrostyloid space)Not included unless involved Included IncludedLevel Ib Not included unless involved Included Included in node positivepatients17.3.2CTV of the Primary DiseaseIn the reported series of NPC treated with IMRT,methods of CTV delineation varied; however, mostseries reported a superb local control of 90% or abovein the primary disease (Lee et al. 2002; Lin et al. 2009;Wolden et al. 2006; Kam et al. 2004; Tham et al.2009a). The CTV delineated in IMRT for NPC islargely derived from our experience of conventionalradiation therapy planning. Although local control isreportedly superb using the current arrangements ofCTV, whether such an arrangement is necessary andcan be reduced has not been fully addressed.According to the RTOG 0615 protocol, the CTV ofthe primary disease should include the entire nasopharynx,anterior 1/2 to 2/3 of the clivus (entire clivus, ifinvolved), skull base (foramen ovale and rotundumbilaterally must be included for all cases), pterygoidfossae, parapharyngeal space, inferior sphenoid sinus,and posterior fourth to third of the nasal cavity andmaxillary sinuses to ensure pterygopalatine fossaecoverage. The entire sphenoid sinus and cavernoussinus should be included in patients with T3, T4, bulkydisease involving the roof of the nasopharynx (Lee etal. 2006). The outermost boundary of the above-mentionedCTV should be at least 10 mm from the GTV ofthe primary disease. Currently, the RTOG protocol recommends59.4 Gy to the CTVs listed above.Such coverage is largely derived from our previousexperience of conventional radiation therapy forNPC, and typically encompasses a large volume.Although outcomes from such CTV arrangementsproduced superb local and regional control rates,whether it is necessary to encompass all normal adjacentstructures as described above in radiation therapyfor NPC, even in T1 and T2 diseases, is debatable.Isolated marginal local recurrence in the peripheryof conventional treatment portal is minimal in anyreports even in patients with T3 or T4 diseases (Chauet al. 2001, 2007). In a prospective series that included323 NPC patients treated with IMRT, Lin et al. (2009)utilized a “reduced-volume” technique and includeda limited volume in target delineation in both theprimary disease area and to a lesser extent, in theneck lymph node area. The CTVs delineated in thestudy reported by Lin et al. and required by the RTOG0225 and 0615 are listed in Table 17.5. At 30 monthsfollow-up, the treatment outcome including local andregional control, as well as disease-free survival andoverall survival rates were similar to historical data,and were 95%, 98%, 85%, and 90%, respectively (Linet al. 2009). Ten patients experienced local recurrencewithin the delineated GTV, and two patients had