11 Lip and buccal mucosa

Lip and buccal mucosa

8

THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 10/05/2019

cosmetic radiation damage is greater than the gain in local control expected from a dose increase above 70 Gy. The total dose for LDR brachytherapy was 25-30 Gy when it was used as a boost after 45-50 Gy of external beam irradiation. With PDR, the dose per pulse is between 40-80 cGy every hour to administer a total of 55-65 Gy, in five days, similar to LDR [22-23]. With HDR two fractions per day, separated at least 6 hours are used. A dose per fraction between 4 and 5 Gy are the most common employed. With rigid needles, the homogeneity index is over 80% and a higher dose per fraction can be used without risk. A dose of 5 Gy x 9 fractions to a total dose of 45 Gy (EQD2: 56.25 Gy) in five days allows for starting the treatment on Monday and withdraw the needles on Friday, keeping the same 5-days period as required for LDR [24]. In postoperative cases, 4.5 Gy x 9 fractions (EQD2: 48.9 Gy) is enough. Higher doses per fraction, 5.3Gy or 5.7Gy have been used. For the plastic tube technique, same doses can be used, but the homogeneity is not so good, and there can be hot spots. In these cases the DNR should be less than 0.36, what means that one third of the volume is receiving 150% of the prescribed dose [25]. Therefore a lower dose per fraction may be advisable: 4 Gy x 10-12 fractions (EQD2: 46.6 – 56 Gy). The EQD2 concept should be used with caution in H&N brachytherapy because the calculated values for the equi-effective dose are often lower than expected for a curative tumour effect with EBRT. (see chapter on General Aspects of Head and Neck Brachytherapy).

than prescribed by Paris System rules [26]. Beauvois reported even that when the entire lip was treated (this was the treatment policy in Nancy after 1985) no contralateral lip recurrences were seen [16]. In the large 1993 GEC-ESTRO brachytherapy for lip cancer study (brachytherapy for lip cancer study 224 recurrences in 2794 patients were noted over a long follow up time (up to over 15 years) with an annual probability for recurrence rate of less than 1% [27]. The local disease free survival probability (DFS) at 5, 10 and 15 years follow-up was respectively 94% 90% and 89%. Significant higher local control rates were seen in lower lip cancers, and worse in commissural lesions (p=0.00001). A highly significant difference was noted between the local control rates according to T-stage (p=0.00001). For T1 tumours, the 5, 10 and 15 years DFS were respectively 95%, 91% and 90%; for T2, they were 91%, 89% and 86%; and for T3 in 82%, 78% and 78%. Local control rates were worse in poorly differentiated tumours: the 5 and 10 year local control rates being 97% and 95% for WHO I lesions, 95% and 80% for WHO II, and 80% and 77% inWHO III lesions. There were no differences in local control rates for patients treated with combined surgery and brachytherapy versus patients treated with BRT alone. Besides T size, the brachytherapy dose delivered is the major predictor for local control. The data suggest that 60 - 65 Gy is optimal to treat T1 (2 - 3% local failure at 5 years) and 65 - 70 Gy optimal to treat T2 lesions (3.1-4% local failure rate at 5 years). These local control rates compare favourably with surgical series (6 - 30% local failures) [13-16]. In addition, local recurrences can be salvaged in 80 % of cases by surgery [16-20-21]. 12.1.1 Local control with PDR There are some series that use pulsed dose rate brachytherapy (PDR), with sessions of 0.83 to 1 Gy repeated every hour, to achieve doses similar to those administered with low rate [22-23]. Results of HDR and PDR are shown in table 2. 12.1.2 Local control with HDR The first publication with HDR-BT in lip appeared in 2003 with 39 cases [24]. The average follow-up was short, 18 months, with two daily fractions of 5 to 5.3 Gy in 8 or 9 fractions, reaching a control of 95% in T 1 and T 2 and 74% in T 4. It was found that the acute and chronic effects were similar to those of low rate, maintaining good function. Another work, published in 2005 on 28 patients, used acrylic moulds with plastic tubes for superficial or contact brachytherapy [37]. A dose of 1.8 Gy per day five days per week, up to 60-65 Gy in small tumours and up to 75-80 Gy in bulky ones was used and no relapses were seen. Good or excellent aesthetic results were reported in 96% of cases, without complications. Another studywith 24 T1-2 patients, 18with exclusive brachytherapy and 6 after surgery, used an average dose per fraction of 5.7 Gy and an average of 7 fractions to obtain a mean total dose of 35 Gy, prescribed at 80% or 3 -5mm depth from the tumour. The average duration of the treatment was 12 days. With a follow-up of 32 months, control was achieved in 87.5% [38]. In 2010 21 lip cancer patients were reported treated with HDR, giving 45-50 Gy in 9 -10 fractions, with 32 months of median follow-up. It was concluded that HDR seems to be as good as LDR [39]. Another study includes 70 cases of LDR and 33 of HDR, with doses using different fractions, using plastic tubes, reporting a control rate of 93%with no difference between LDR andHDR [40].

11. MONITORING

Before the treatment check the dwell times, the length of the tubes or needles, and the separation between them. Daily control of the position of source carriers and protector device is mandatory. When rigid needles are fixed with a template outside the tumour, they can be placed again and removed after every session, for better comfort. A soft diet is better, but usually no feeding tube is required. Simple analgesics may be indicated. Acute side effects such as mucositis (in the second week) and epidermitis (in the third to fourth week) can be mild to severe and have to be treated symptomatically with topical applications.

12. RESULTS

12.1 Results in lip carcinoma 12.1.1 Local control with LDR

Overview of the literature shows local control rates of 90 - 95% at 5 years (Table 1) for Ir-192 LDR brachytherapy following the Paris system implantation rules. The results are somewhat better in T1 (0 - 5%) five year local failure rates than in T2 disease: 2.1% - 8.2% [13-21]. They seem to be worse when Paris system implantation rules are not followed: local recurrences were 1/21 (4.8%) when active source lengths were long enough for covering the PTV and were 7/51 (13.7%) when source lengths were shorter