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Nasopharyngeal brachytherapy
This document provides information about nasopharyngeal brachytherapy for the treatment of cancer. It discusses the anatomy of the nasopharynx, indications for brachytherapy including as a boost after external beam radiation or for localized recurrences. Several techniques for nasopharyngeal brachytherapy are described including customized moulds, Rotterdam and Massachusetts General Hospital applicators, and transnasal permanent implants. Typical dose prescriptions and fractionation schedules are provided. Results from studies show brachytherapy improves local control and survival rates compared to external beam radiation alone, especially for early stage tumors.
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Nasopharyngeal brachytherapy
- 1. Nasopharyngeal Brachytherapy Dr. AshutoshMukherji Associate Professor Department of Radiotherapy, Regional Cancer Centre, JIPMER
- 2. INTRODUCTION • Cancer ofthe nasopharynx is relatively uncommon in Western countries (0.5-2/1,00,000/yr), but more frequent in parts of Asia (30-80/1,00,000/yr) and North Africa (8-12/100,000/yr). • Mostly Inoperable, spread early to cervical lymph nodes, distant metastases is fairly well known. • Main prognosis factors are the local extension of the tumours (invasion of the base of skull and paralysis of the cranial nerves) and lymph node metastasis. 2
- 3. ANATOMY……. 3 • The nasopharyngealcavity communicates anteriorly with the nasal cavities through the choanae and inferiorly with the oropharynx. • The sphenoid body limits it superiorly, the first two vertebrae posteriorly, and the soft palate inferiorly. • The Eustachian tubes open into its lateral walls, in front of the fossa of Rosenmüller.
- 4. INDICATIONS • Brachytherapy applicationsof the nasopharynx are restricted to – Boost for minimal residual local disease after external irradiation – Salvage therapy for well-circumscribed and superficial local recurrences limited to the nasopharyngeal cavity without involvement of the underlying bone or extending to oropharynx or nasal cavities 4
- 5. • Nasopharynx deeplysituated and surrounded by bone, vessels and nerves usually endocavitary techniques can be performed. • CTV thickness should not exceed 10 mm • Tumours extending into the nasal cavities or the oropharynx should not be accepted for brachytherapy. 5
- 6. TARGET VOLUME • ThePTV defined by endoscopy, CT-Scan and MRI. • Most tumours are situated at the roof of the nasopharynx. 6 In central tumours, the CTV may include both roof and lateral walls. In well-lateralised tumours, CTV will include the roof and one lateral wall. In most cases, the depth of PTV does not exceed 10 mm.
- 7. TECHNIQUES APPLIED • CUSTOMISEDMOULD • ROTTERDAM NASOPHARYNGEAL APPLICATOR • MASSACHUSETTS GENERAL HOSPITAL TECHNIQUE • TRANSNASAL PERMANENT INTERSTITIAL IMPLANTS 7
- 8. CUSTOMISED MOULD TECHNIQUE • Sagittallyoriented plastic tubes are fixed on the surface of a rigid acrylic applicator, made from an individual impression of the nasopharyngeal cavity. • Procedure is therefore performed under neuroleptic analgesia • Nasal secretions are suctioned and the mucous membranes anaesthetised with 5% xylocaine spray to avoid gag reflex or pain. • First rubber catheters are passed through both nostrils and brought out of the mouth; the oral ends of these are tied to a dummy applicator coated with silicone paste. 8
- 9. • This pastecoated dummy applicator is pulled into the nasopharynx and paste forms an impression of the naspharyngeal cavity. • Then from this impression a negative POP mould is prepared from which the actual acrylic mould is made with 2-5 mm thick walls. • Boundaries of the tumour are highlighted in ink and source position that will provide optimal coverage of the lesion are indicated with sagittal lines. • Spacing between sources varies from 10 to 15 mm. In average patients, the rule for catheter implantation is 2 catheters per wall or 3 catheters for 2 walls or 4 catheters for 3 walls (roof and 2 walls) 9
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- 11. ROTTERDAM APPLICATOR • Ismade of soft silicone • Well tolerated by patient • Insertion procedure is same as for customised mould • The applicator can remain in situ for the duration of the treatment, from 2 to 6 days. • The two silicone tubes, can accommodate standard 6 French afterloading catheters. • The legs of the applicator sort through the nostrils and are fixed with a silicone bridge, pushed against the nasal septum. 11
- 12.
- 13. MASSACHUSETTS GENERAL HOSPITAL TECHNIQUE •This technique uses two paediatric endotracheal tubes with inner and outer diameter of 5 and 6.8 mm, respectively. They can be afterloaded each with 20-mg radium-equivalent caesium 137 slugs or stepping source PDR or HDR afterloaders. • After topical anaesthesia endotracheal tubes are introduced into the nasopharynx through the nostrils and under fluoroscopic control, the distal tip of the dummy sources are placed at the free edge of the soft palate posteriorly and at the posterior wall of the maxillary sinus anteriorly. • An inflated balloon, attached to the distal end of the endotracheal tube, is used to anchor the tubes and to create a distance between the radiation sources and the nasopharyngeal vault to obtain a better depth dose. 13
- 14. TRANSNASAL PERMANENT INTERSTITIAL IMPLANTS •Using fibre-optic endoscopy and under direct visualisation, hollow after- loading needles are introduced into the nasal passages and are advanced through the posterior choanae, and inserted into the mucosal surface. • Radioactive I-125 seeds are then introduced submucosally through these needles, and the needles are withdrawn. 14
- 15. • The doseprescribed to an isodose covering the surface of the underlying bone, at 5 - 10 mm from the mucosal surface. • Dose distribution optimized when possible so that the reference isodose follows the bone surface. 15
- 16. • Brachytherapy usedto deliver BOOST dose to a small volume after a full course of external beam radiation therapy. • In LDR brachy, the active source is tailored to the nasopharynx proper that is to the distance between the ‘Node of Rouviere’ (at the level of the C-I vertebral body) and the pterygoid plates. The Ir-192 source is removed after a dose of 11 Gy is delivered to the nasopharynx “tumour tissue” (TT) point. • For HDR, a boost dose of 9 Gy in 3 fractions of 3 Gy each is delivered with a minimum interval of 6 hours between fractions prescribed as described in previous slides. 16
- 17. DOSES PRESCRIBED • Wangdelivered with LDR afterloading intracavitary implant 7 - 12 Gy at 5 mm below the mucosa. • Levendag et al. deliver after a rest period of 1 - 2 weeks, a boost dose to the primary site with HDR brachytherapy, with two 3 Gy fractions per day at 6 hour interval. Total of fractions is 6 (after 60 Gy external beam irradiation) for T1 - 3 tumours, and 4 (after 70 Gy external beam irradiation) for T4 tumours. • For recurrent tumour recurring, 60 Gy is delivered in roughly 6 days with a LDR technique 17
- 18.
- 19. RESULTS • Since 1974,at Massachusetts General Hospital, afterloading intracavitary implant has been carried out as a routine procedure to deliver a dose of 7- 12 Gy as a boost to the nasopharynx for most T1 and T2 and occasionally T3 lesions 19 5 year survival rates in MGH in nasopharyngeal cancers
- 20. RESULTS • At Rotterdam,in a prospective study of 41 patients treated with 60-70 Gy external beam radiation therapy and 12 - 18 Gy HDR brachytherapy boost, the 5-year local relapse free survival rate of T1 - 2 cancer patients (n = 29) was 96% versus 57% for T4 cancer patients (n = 12) (p = 0.002) 20 5 year actuarial survival rates in MGH in recurrent nasopharyngeal cancers
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- 25. RESULTS • 18–24% ofpatients with nasopharyngeal carcinoma develop local recurrences • Brachytherapy is an important modality for treatment of localised small recurrences. • Other modalities are: – Cyberknife RadioSurgery – SBRT – IMRT • The period elapsed before development of local recurrence is a significant factor influencing disease-free survival times. 25
- 26. Causes of relapsein Ca Nasopharynx Failure= 192/610 (31%) Local Failure ONLY= 52% Distance metastasis=27% Death= 156/610 Cause of death: Local Relapse only= 44% Distance mets= 28% Local control after relapse improves survival Sun JA et al, Asian Pacific J 2007
- 27. Surgery for RecNasopharynx - ONLY few prospective reports - Skull base/ bone erosion & carotid artery erosion not considered for surgery - 5-Yr OS: 40-60% - 20% palatal fistula
- 28.
- 29. Liu et al.Radiation Oncology 2013 SBRT: persistent Nasopharyngeal Ca
- 30. -No difference inmaximum spinal cord dose and mean parotid doses between HDR & CK boost plans; In IMRT plan, higher ipsi-lateral parotid dose Comparison of three plans (Dose: 24 Gy/6#) IMRT boost HDR boost CK boost Spinal cord Dmax (Gy) 7.4 1.2 1.5 Ipsi-lateral parotid Mean dose (Gy) 8.3 3.1 2.1 Conta-lateral parotid Mean dose (Gy) 3.7 1.4 1.7 (n=11) Dutta et al; CK Society meeting San Francisco 2010
- 31. 31 • Study fromHong Kong • 34 patients with locally persistent NPC who were treated during 1992–2000 with HDR intracavitary brachytherapy were analyzed retrospectively. All patients had T2b disease at initial diagnosis. • An improvement in the 5-year actuarial local failure-free survival rate (brachytherapy group vs. ERT group: 96.9% vs. 81.5%; P 0.024), the disease specific survival rate (84.5% vs. 68.1%; P 0.021), and the overall survival rate (78.3% vs. 63.1%; P 0.034) was seen in the group with locally persistent NPC salvaged with brachytherapy.
- 32.