Page 10 - ARNM-1-1

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

prognostic factor for survival. However, recurrent HNC high spatial resolution and better soft-tissue contrast, MRI
(rHNC) was still reported in the range of 16% – 25% guidance has faced a lot of technical challenges, such as the
for high-risk HNC after surgery and 17% – 52% for non-compatibility of magnetic materials in the magnet,
unresectable HNC after radiochemotherapy, and more relatively long scan time, and high prices at the current
than 65% of patients with squamous cell cancer [2-4] . settings, that MRI guidance is not recommended as a
Surgery is still an effective therapy for rHNC, providing the routine standard BT approach .
[19]
greatest possible cure while suffering 30% – 50% of local
and/or regional recurrence with a 5-year overall survival 2.2. Intra- or post-operative I-125 RSI-BT
(OS) rate of 40% . Unfortunately, the majority of rHNC applications
[5]
are unresectable, 40% of re-irradiated patients developing HNC involving boney structures, blood vessels, or critical
severe toxicities (>Grade 3/4), and nearly 10% of patients nerve positions can hardly yield a complete resection.
suffer from treatment-related death [5,6] . Preliminary studies suggest that RSI-BT may be used as a
Brachytherapy (BT) is a specific form of radiotherapy combination therapy during surgery or as a savage therapy
(RT). The utilization of high-dose-rate (HDR) BT in HNC after surgery to improve the LC in patients with complex
has been recommended to take advantage of its rapid diseases, avoiding exaggerated resection to adjacent
dose falling-off characteristics. This approach offers the normal tissues, decreasing the side effects, and further
potential to deliver concentrated, high doses to the tumor prolonging survival.
while minimizing the risk of complications in surrounding Zhang et al. have the first to report the results
[20]
normal tissue. BT has a history of more than 100 years of a study involving 12 patients with locally advanced
after the radioactive radium-226 isotope was discovered malignant parotid gland tumors. The patients were
by Pierre and Marie Curie in 1898, which was first used treated with a combination of I-125 RSI-BT and surgery,
to treat prostate carcinoma in France in 1900 [7,8] . HDR with preservation of the facial nerve. The results showed
(defined as a dose rate of >12 Gy/h) or low-dose-rate (LDR that none of the patients had tumor recurrence during
[defined as a dose rate of <2 Gy/h]) BT is now commonly the follow-up period of 50 – 74 months. The facial nerve
used as monotherapy or in combination with EBRT for the recovered to normal function 6 months postoperatively for
treatments of prostate, breast, cervix, and skin cancers [9-11] . all patients. I-125 RSI-BT is now considered an alternative
Permanent seed implantation is the major form of option for locally advanced-stage malignant parotid
LDR-BT. Two radioactive seeds (i.e., I-125 and Pd-103) gland tumors with preservation of the facial nerve. In a
[21]
have been widely used since the past century, precisely subsequent trial conducted by Huang et al., 12 patients
in 1980 . I-125 sealed radioactive sources emit gamma with recurrent or locally advanced maxillary cancers were
[12]
rays with an energy of 35.5 keV and a half-value thickness included in the study. These patients had positive residual
of lead of 0.025 mm and 1.7 cm in the tissue, making disease following surgery and underwent treatment with
radiation protection highly effective. Pd-103 sealed sources I-125 RSI-BT. The radioactivity administered per seed
emit a mixture of gamma-ray and characteristic radiation ranged from 18.5 to 33.3 MBq, and the prescribed dose
with an energy of 21 keV with a half-life time of 17 days. (PD) ranged from 80 to 160 Gy. The study observed
The diameter and length of both seeds are 4.5 mm and encouraging long-term outcomes, with LC rates of 83.3%
0.8 mm, respectively. Since the production of 6711 type of and 66.7% at 3 and 5 years, respectively, and a mean LC
I-125 seed in 2000, the treatments for many refractory or time of 53.5 ± 3.79 months. The OS rates at 3 and 5 years
recurrent carcinomas have been investigated using I-125 were 91.7% and 71.4%, respectively, with a mean survival
seed implantation BT with image guidance in China [13-18] . time (MST) of 56.6 ± 2.99 months. Notably, two patients
This review aims to summarize permanent I-125 seed succumbed to local recurrence and one to lung metastasis.
implantation in China. Fortunately, no severe complications were reported
during follow-up evaluations. In a study conducted by
2. I-125 radioactive seed implantation-BT Mao et al. , a total of 29 patients diagnosed with acinic
[22]
(RSI-BT) for HNC cell carcinoma (ACC) were treated with I-125 RSI-BT.
The median actuarial D90 was 177 Gy, and the treatment
2.1. RSI-BT guidance techniques was administered 3 – 41 days following surgery (median:
The available image guidance techniques for I-125 RSI-BT 14 days). Each seed had radioactivity ranging from 18.5 to
are intra-operative ultrasound, computed tomography 33.3 MBq, and PD varied from 80 to 120 Gy. The findings
(CT), magnetic resonance imaging (MRI), and navigator, of the study revealed favorable long-term outcomes for
with the most common in the clinic being ultrasound or the patients. The LC rates at 3, 5, and 10 years were 93.1%,
CT guidance. Although MRI provides the advantage of 88.7%, and 88.7%, respectively. Similarly, the OS rates at the

Volume 1 Issue 1 (2023) 2 https://doi.org/10.36922/arnm.0907