Page 31 - ARNM-2-4

Advances in Radiotherapy
& Nuclear Medicine 3D-PT-assisted CT-guided I RSI
125

intraluminal irradiation, interstitial irradiation, “Head and Neck Cancer” or “3D-printing Template.” The
intraoperative irradiation, and mold irradiation. Among consensus statement does not include discussions on other
these modalities, high dose rate after loading brachytherapy treatment modalities such as external beam radiotherapy,
and low dose rate interstitial seed implantation chemotherapy, or immunotherapy.
brachytherapy are the most commonly employed
techniques. High dose rate after loading brachytherapy is 3. Findings
primarily utilized for treating cervical cancer, endometrial 3.1. Basic concepts of interstitial RSI
cancer, breast cancer, skin cancer, and prostate cancer.
This technique is characterized by significant fractionation Interstitial RSI is a form of permanent brachytherapy that
and short treatment courses. Interstitial seed implantation adheres to the principles of radiation therapy. This principle
brachytherapy is mainly employed for recurrent HNC, includes delineating the target area, defining organs at risk
lung cancer, pancreatic cancer, prostate cancer, soft-tissue (OARs), setting the prescribed dose, and establishing dose
tumors, and various pelvic recurrent metastatic cancer constraints for OARs. 27,28
types. It is characterized by its single-session completion 3.1.1. Definition of target area and OARs
26
using minimally invasive techniques.
According to the International Commission on Radiation
2.2. The consensus formation process Units and Measurements Report 83, the target area and
27
The consensus formation process involved active OARs are defined as follows:
participation from various medical associations and i. Gross tumor volume (GTV): This represents the
centers, including the China Society for Radiation visible lesion with a specific shape identified through
Oncology, the Expert Committee on Radiation imaging modalities and clinical examinations.
Oncology, the Chinese Medical Doctor Association, the ii. Clinical target volume (CTV): This encompasses the
Brachytherapy and Intelligent Radiotherapy Division of GTV, subclinical foci, and areas potentially affected by
the Chinese Nuclear Society, and the Beijing Radiation the tumor.
Therapy Quality Control and Improvement Center. Experts iii. Planning target volume (PTV): This includes the CTV
from diverse departments, such as radiation therapy, with appropriate expansion to account for patient
surgery, interventional radiology, internal medicine, organ motion, daily positioning variability, target
ultrasound, and nuclear medicine, were convened to area location during treatment, and changes in the
form a committee. Under the guidance of a chairman, target volume. However, PTV is primarily applicable
these experts collaborated to draft an initial version of the in external beam radiation and is rarely considered in
consensus document, which was subsequently circulated interstitial RSI.
among committee members for feedback. Extensive iv. OAR: This refers to adjacent normal tissues or organs
discussions and deliberations within the committee covered by the irradiated area.
ultimately led to a finalized consensus. The scope of this 3.1.2. Prescription dose and evaluation parameters
consensus was specifically concentrated on the utilization for the target area
of 3D-PTs to guide seed implantation brachytherapy for
recurrent HNC. 3.1.2.1. Prescription dose
The prescription dose refers to the radiation dose that can
2.3. Purpose and target audience of the consensus
locally control the tumor based on evidence-based medicine
The purpose of the consensus was to clarify the or clinical practice. However, there is a notable absence of
responsibilities of doctors, physicists, therapists, and prospective studies focused on dose escalation in interstitial
nurses involved in brachytherapy using radioactive seeds. RSI for HNC. According to the American Brachytherapy
This consensus aims to provide a clear understanding Society, the recommended prescription dose for prostate
of the indications, technical standards, and operational cancer treated with 125 I seed implantation ranges from
procedures associated with seed implantation, ultimately 140 to 160 Gy. Post-operative evaluations should confirm
benefiting cancer patients. that the dose received by 90% of the target volume (D90)
meets or exceeds 100% of the prescribed dose. In addition,
2.4. Literature search external beam radiation is typically prescribed at a dose of
The consensus incorporated studies published up to 115 Gy. Referring to previous studies on prostate cancer
9
December 2023, encompassing both printed and online and HNC treated with radioactive seeds, recommended
sources. The search was conducted using the Medline doses are summarized as follows: for patients previously
database with MeSH terms, such as “Brachytherapy” and treated with radiation therapy: 90 – 120 Gy; for those who

Volume 2 Issue 4 (2024) 4 doi: 10.36922/arnm.4212