10 General Aspects of Head and Neck Brachytherapy

General Aspects of Head and Neck Brachytherapy

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 30/01/2019

boost derived from a better dose distribution has been described (figure 1) [11]. Finally, combined EBRT and brachytherapy may also be used in d) patients with tumors with a poor regression after EBRT and in whom dose escalation is advisable and in e) patients with lesions subjected to position uncertainty in spite of restraint devices (i.e, anterior tongue). Local control rates in excess of 80% are commonly reported in different tumor sites treated with a standard combination of 45- 50 Gy of EBRT and 15-20 Gy of LDR brachytherapy (or PDR/ HDR equivalent). 6.3. Brachytherapy combined with surgery Exclusive brachytherapy can be used after surgery when there is a well-delineated and accessible CTV. Oral cavity tumor stages cT1, cT2, N0 that are managed primarily with surgery can be treated with adjuvant brachytherapy alone if the surgical pathology reveals that the neck is negative and that there is indication for postoperative irradiation of the primary tumor bed due to close or positive margins, lymphovascular space involvement or perineural invasion. Implant can be performed postoperatively, 4 to 6 weeks after surgery (postoperative brachytherapy) once the patient has recovered from the surgical procedure or intraoperatively (perioperative brachytherapy) in those cases in which the need for adjuvant treatment is presumed due to the characteristics of the tumor. Brachytherapy can be used as a boost in patients selected for combined treatment with surgery and external irradiation or chemoradiation.The areas selected for brachytherapy boost should be those with a higher probability of residual disease such as the tumor bed (close or positive surgical margins) and large metastatic nodes (extracapsular spread). Unirradiated local or regional recurrences can also be treated through this treatment approach. The treatment sequence may be quite variable but in general, it is preferable to performHNBT at the time of surgery in patients who require neck brachytherapy because neck implantation is easier when performed intraoperatively rather than postoperatively. Hence, if surgery is performed first and the neck needs to be implanted, HN BT boost can be done perioperatively followed by external irradiation or chemoradiation postoperatively. However, if external irradiation or chemoradiation is done first and surgery is planned for residual disease (i.e, large metastatic neck nodes), HN BT should be postponed until surgical resection is planned. 6.4. Brachytherapy combined with Surgery and External Irradiation or Chemoradiation

some difficult oropharyngeal locations, the assistance of the ENT surgeon may be required. In all cases, an ENT surgeon should be on-call during implantation and at removal. The medical team is completed by specialized anesthesiology, radiation oncology and in-patient nursing staff to take care of the patient while in the recovery room, in the radiation facility or during hospital stay. 7.2. Techniques and rules Interstitial brachytherapy using the submental route is the most frequently used technique in patients treated with afterloading techniques.The submental approach allows access to the oral cavity and the oropharynx. In general, HN BT area is usually delivered through fixed applicators (plastic tubes or steel needles) inserted with amargin of 5–10mmaround the CTV. Former techniques that involved the use of loops have been gradually replaced by variants of the loop technique such as the non-looping loop technique [12] than can be seen in figure 6. Permanent implants are only rarely used in this setting and will not be discussed here. Other techniques used for afterloading include intraoral mold brachytherapy, perioperative mold brachytherapy and hand-free perioperative brachytherapy. In mold brachytherapy, the implant is built into a mold (figure 7) that is placed intraorally onto shallow lesions arising in non-mobile areas such as the hard palate or the gum [13]. In perioperative mold brachytherapy, custom-made molds are placed in the surgical bed to deliver perioperative brachytherapy such as in the AMORE protocol for advanced and recurrent non- orbital rhabdomyosarcoma of the head and neck. In perioperative brachytherapy, free-hand catheters are placed through the skin into the tumor bed at the time of surgery (Figure 8). We recommend that catheter geometry and intercatheter distance according to specific rules belonging to a system should be always kept in mind at the time of implantation. Although the use of modern TPS has reduced the need for rigid geometrical rules that cannot always be applied in HNBT due to anatomical constraints, it is always wise to followwhen possible reproducible implantation and dosimetric rules with proven results over decades such as those of the Paris system [3]. (Figure 9) 8.1. Timing and characteristics of the CT/MRI study CT planning should be done in all cases. In patients in whom severe CT artifacts are produced by the presence of reconstruction plates, teeth implants, etc. a return to the old orthogonal film techniquemay be the only option to obtain a reasonable dosimetry. Nowadays, we also have the possibility to perform a MRI which can be helpful to delineate the tumor limits and can be fused with CT images.The CT study should be done as soon as possible once the patient is stable and ready for transportation. There is no reason to delay the CT due to the risk of infection andmechanical trauma associated with the implant. A CT scan slice thickness of 3 to 5 mm is adequate in most cases. Intravenous contrast is useful in defining the vascular structures and should be used whenever possible, especially in lesions recurrent after prior irradiation. 8. PLANNING

7. IMPLANTATION

7.1. Staff HN BT should be performed by an experienced Radiation Oncologist with advanced brachytherapy skills assisted by an anesthesiologist. Although local anesthesia or local anesthesia with sedation can be used in some cases, general anesthesia usually provides the level of comfort and safety required by the patient and the medical staff during HN BT. The radiation oncologist should perform HN BT with at least one assistant although in