Fig. 10.1
Insertion under fluoroscopy guidance
Fig. 10.2
Monitor view
Fig. 10.3
Fluoroscopy before introducing the applicator
Fig. 10.4
Fluoroscopy with applicator in position
Fig. 10.5
Catheter 5F with dummy source
We must be careful and delineate the possible organs at risk (great vessels, esophagus, etc.) to limit the dose they receive. When we use a simple 5F endoluminal tube, we must be aware that distance to the airway walls is not symmetrical, unless we use a device equipped with a centering method (balloon, protective cover, etc.). With CT planning, GTV is better covered and radiation of critical structures reduced [3].
Usually PTL is between 4 and 6 cm, and the targeted area is at 10 mm from the center of the source. With CT planning, distance to the target zone can be pointed more accurately, ranging between 5 to 10 mm [4] (Figs. 10.6, 10.7, 10.8, and 10.9). When there is an anatomical curve, dose can be increased at the concave portion and decreased at the convex part. This correction can be of benefit depending upon tumoral location in the airway [4]. When a metallic stent is in place, we must be aware that the dose can increase in its immediate vicinity.
Fig. 10.6
Planning
Fig. 10.7
Dose distribution and histogram
Fig. 10.8
Another case
Fig. 10.9
Shape of the 100% isodose
Before administering the treatment, we must check the ruler mark on the tube at the level of the nostril. We can repeat fluoroscopy to check if the catheter has moved or kinked. Then we connect the tube to the HDR and administer the calculated dose during a short period of time, only few minutes (Figs. 10.10 and 10.11). After the procedure, the tube is easily removed. Patient should be treated maintainig the same body position as the used during CT scanning.
Fig. 10.10
Treatment at the HDR bunker
Fig. 10.11
Detail of HDR treatment
To standardize dose reporting and comparison, we must state not only the target volume but also the dose at 1 cm from the catheter center and the one applied to the sorrounding organs at risk.
The use of appropriate dose reporting, such as the equivalent dose in 2 Gy per fraction (EQD2), should be encouraged when sharing results, particularly when EBRT and brachytherapy are used in combination. This allows more accurate comparison between studies [4].
Fractionation
The fractionation varies: for curative intent, 6 weekly fractions of 5 Gy is the most commonly used scheme, although there is a great variability ([3–5], see Tables 10.1 and 10.2). When combined with external radiation, one of the most used is 50 Gy plus 3 fractions of 5 Gy [3]. For palliative intention, we tend to administer less fractions and more dose per fraction, in order to diminish patients discomfort [6]. In that case, we would choose 1–2 fractions of 7.5–10 Gy (see Table 10.3).
Table 10.1
Table of fractionations used
First author | Brachytherapy | Distancefrom source | External beamradiotherapy |
|---|---|---|---|
Macha | 3 × 10.0 Gy | 10 mm | – |
Speiser (retrospective) | 3 × 7.5 Gy | 10 mm | – |
3 × 10.0 Gy | 10 mm | – | |
3 × 10.0 Gy | 5 mm | – | |
Bedwinek | 3 × 6.0 Gy | 10 mm | – |
Mantz (matched pair) | 3 × 5.0–7.0 Gy | 10 mm | 36 × 1.8 Gy (mean) |
– | – | 36 × 1.8 Gy (mean) | |
Huber (randomized) | 4 × 3.8 Gy | 10 mm | – |
2 × 7.2 Gy | 10 mm | – | |
Mallick (randomized) | 2 × 8.0 Gy | 10 mm | 10 × 3.0 Gy |
1 × 10.0 Gy | 10 mm | 10 × 3.0 Gy | |
1 × 15.0 Gy | 10 mm | – | |
Stout (randomized) | 1 × 15.0 Gy
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