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Advances in Radiotherapy
& Nuclear Medicine Seed implantation head-and-neck carcinoma

seeds may cause normal tissue damage depending on the dose distribution of the targets aligned well with the pre-
number and location. plan requirement.
In a study by Fan et al. , a total of 321 patients with 6.2. Navigator-assisted I-125 RSI-BT for HNC:
[44]
parotid cancer who underwent permanent parotid BT
[45]
were analyzed. Routine follow-up included the evaluation Chen et al. reported on 30 pediatric patients with skull
of head-and-neck CT scans and chest X-rays. Seed base tumors treated with I-125 RSI. The 1- and 2-year LC
reconstruction and migrated seed detection from the rates were 96.7% and 74.8%, respectively. The 1- and 2-year
original implanted region were performed using Mimics OS was 93.3% and 72.2%, respectively. No severe acute
software and Geomagic Studio, respectively. Post-plan toxicity was observed. Severe late toxicities were observed
implant dosimetry analysis was conducted if the seeds in 1/30 (3.33%) patients. The utilization of I-125 RSI-BT has
remained in their emitting count after seed migration. demonstrated effectiveness and safety in the management
Adverse clinical effects resulting from seed embolization of pediatric skull base tumors, yielding satisfactory
to the lung were documented. Among 321 parotid BT cosmetic and functional outcomes. The cosmetic and
patients, the presence of migrated seeds was identified functional outcome results were better than post-surgical
on chest X-rays in six patients. The incidence rate of seed changes and deformity or the wide-field EBRT changes
migration was determined to be 1.87% (6/321), with that would be expected from either modality.
individual seed migration occurring at a rate of 0.04% Xu et al. reported on 32 patients with ACC involving the
[46]
(6/15218 seeds). It was observed that all migrated seeds skull base treated with I-125 RSI-BT. The PD ranged from 60
originated from the retromandibular region. Importantly, to 120 Gy. The 1- and 3-year OS rates were 93.3% and 62.6%,
no adverse dosimetric consequences were observed in the the 1- and 3-year PFS rates were 90.0% and 46.4%, and the
target region, and no pulmonary symptoms were reported 1- and 3-year DFS rates were 91.7% and 61.1%, respectively.
by any patient in this study. Survival was significantly associated with local recurrence
(p = 0.04) and distant metastasis except in the lung (p = 0.05).
6. Navigator-assisted I-125 RSI-BT The rate of severe chronic adverse RT reactions was 3.1%,
6.1. Accuracy of navigator-assisted I-125 RSI-BT and no severe acute adverse RT reactions were observed.
Image guidance combined with 3D-PT has increasingly I-125 RSI-BT appears to be an effective and safe treatment
improved the accuracy and precision of I-125 RSI-BT, for recurrent ACC involving the skull base with a history
but the seed needles’ position often deviates from the of prior RT. Local control with BT could provide survival
[47]
pre-planned position due to tumor bleeding, shape benefits even in patients with lung metastasis. Ren et al.
changes, necrosis, or muscle relaxation with antithesis. reported eight patients treated with I-125 RSI-BT assisted
As a result, the real-time position of the needles may not with MRI-Navigator system guidance in the cranial base and
match well with the pre-plan for intra-operative CT scan, orbital apex. The activity of I-125 was 0.5–0.7 mCi (0.6 mCi).
and additional steps are needed to overcome the intra- The clinical results showed five cases of partial response
operative changes or errors. Navigation techniques have (PR) and three cases of no change (NC). The complications
been developed very fast in the recent two decades in included minor bleeding, but no brain tissue necrosis or
surgery, and the navigator system, having been integrated hernia occurred. However, there was no PD description or
into 3D-PT and CT guidance, makes the I-125 RSI-BT the post-plan D90 about the target’s radiation doses.
more accurate, fast, and convenient, which has been well The advantages of navigator-assistant CT-guidance
exploited by Chinese radiation oncologists. for I-125 RSI-BT are as follows: (i) The precision and
According to Zhang et al. , in a study involving ten accuracy have further improved; (ii) intra-operative real-
[15]
patients, a total of 58 needles were successfully inserted time revision of the needles’ arrangement and the template
using computer-assisted techniques with a mean deviation position occurs more rapidly and is convenient; (iii) all
of 5.2 mm. The insertion trajectories and depths of the the procedures become relatively simple and efficacious;
needles varied depending on the region. The range of (iv) the quality control of real-time TPS can be assured, and
the parotid and masseter regions to the infratemporal post-plan dosimetry evaluation has been as expected to
fossa or skull base was 15.7 – 74.6 mm. The range of pre-plan design; and (v) only a 6-month training is needed
the submandibular and retromandibular regions to the for inexperienced interventional radiation oncologists.
infratemporal fossa or skull base was 15.6 – 70.6 mm. The 7. BT-TPS for I-125 RSI-BT
range of the infraorbital to the pterygomandibular region
was 63.7 – 69.7 mm. The range of the periorbital region to Various techniques have been developed for permanent
the infraorbital region was 47.6 – 61.8 mm. Notably, the interstitial BT, especially in relationship with BT-TPS.

Volume 1 Issue 1 (2023) 9 https://doi.org/10.36922/arnm.0907