Stereotactic Body Radiotherapy for Early-Stage Non-Small Cell Lung Cancer: Procedure of the Salah Azaiez Institute in Tunisia

Review Article

Austin J Med Oncol. 2023; 10(1): 1077.

Stereotactic Body Radiotherapy for Early-Stage Non-Small Cell Lung Cancer: Procedure of the Salah Azaiez Institute in Tunisia

Kaabia W*; Mousli A; Zarraa S; Ben Zid K; Yousfi A; Gargouri W; Yahyaoui S; Abidi R; Nasr C

Department of Radiation-Oncology, Salah Azaiez Oncology Institute, Tunis-Tunisia

*Corresponding author: Wael Kaabia Department of Radiation-Oncology, Salah Azaiez Oncology Institute, Tunis-Tunisia. Tel: +216 50492029 Email: [email protected]

Received: September 30, 2023 Accepted: November 06, 2023 Published: November 13, 2023


Stereotactic Body Radiation Therapy (SBRT) revolutionizes the management of lung cancer, providing precise and effective treatment. It delivers high doses of radiation to the tumour site while minimizing damage to healthy tissue. Its short treatment duration and high local control rate make it a treatment option for patients with early-stage lung cancer. SBRT is also useful for inoperable tumours and limited metastases. This article provides a brief overview of the use of SBRT in lung cancer treatment at the radiation-oncology department of the Salah Azaiez Institute in Tunisia.

Keywords: Lung cancer; Radiation therapy; Stereotactic radiotherapy; SBRT

Abbreviations: SBRT: Stereotactic Body Radiotherapy; SABR: Stereotactic Ablative Radiotherapy; ISA: Institute Salah Azaiez; NSCLC: Non-Small Cell Lung Cancer; RFA: Radiofrequency Ablation; CRT: Conventional Radiotherapy; CT: Computed Tomography; PET-CT: Positron Emission Tomography Scan; CBCT: Cone-Beam Computed Tomography; ESTRO: Positron Emission Tomography Scan; ACROP: Advisory Committee for Radiation Oncology Practice; BED: Biological Effective Dose; OAR: Organ At Risk; PRV: Planning at Risk Volume; DVH: Dose Volume Histogram; CTCAE: Common Terminology Criteria for Adverse Events


Stereotactic Body Radiotherapy (SBRT) is a precise radiation therapy technique used to deliver highly focused and accurate radiation beams to extracranial target localization in 1-8 fractions. It integrates modern imaging, simulation, treatment planning and delivery technologies in order to achieve a high gradient of dose with high conformality with the target volume [1]. It is also referred to as “Stereotactic Ablative Radiotherapy” (SABR) since the convergence of the different beams result in creating a hotspot with a rapid falloff of dose outside of the target, which creates a lethal ‘ablative’ effect [2]. SBRT is also shown to induce vascular damage and to have an immunological effect, both of which indirectly causing cell death [3].

Since 2018, our patients have started to benefit from this innovative technique in Tunisia at the Salah Azaiez institute (ISA).

The purpose of this document is to present the SBRT procedure for lung lesions, implemented at our radiotherapy department at ISA. We aim to detail the different steps as well as the required equipment for lung SBRT. This procedural document has been elaborated thanks to the tight collaboration between radiotherapists, medical physicists, and technicians.

I. Indications of SBRT in Non-Small Cell Lung Cancer (NSCLC)

Historically, the mainstay in the treatment of early-stage NSCLC has been anatomical surgical resection through lobectomy, segmentectomy or wedge resection [4]. Other treatment options include conventional radiotherapy or Radiofrequency Ablation (RFA). However, during the last decades, there has been a rising interest in SBRT. Compared to surgery, SBRT is a non-invasive, organ preserving, outpatient treatment, which typically lasts 1-2 weeks without requiring anaesthesia and allowing for an immediate return to activities. Furthermore, while segmentectomy offers a good Local Control (LC) for small lesions less than 20mm reaching 98.1%, this outcome is not maintained for larger lesions falling down to 62.9% [5,6]. Compared to wedge resection, there is a trend toward reduced local recurrence with SBRT (4% v 20%; P .07) [7]. SBRT also achieves high rates of LC attaining 97%, regardless of the size of the tumour [8]. As for RFA, it yields a significantly lower 5-year local control rate compared to SBRT (42% vs 86% p<.001) [9]. It is noteworthy to highlight the CHISEL trial results, comparing Conventional Radiotherapy (CRT) with SBRT, and showing increased local failure (31% vs 14%) and decreased survival (median overall survival of 3 years vs 5 years, p=0·027) in the CRT group [10].

1. Primary lung tumour

SBRT is an option for the management of stage I- II (T1-T2a N0) carcinomas, up to 5cm in size, for inoperable patients (major medical comorbidity, severely limited lung function) or patients refusing surgery [11]. It is also indicated for primary lung tumours without histological evidence, especially, those with increasing size on 2 consecutive CT scans (performed in 8-12 weeks interval), hyper-metabolic on the Positron Emission Tomography (PET-CT) and without any other proven aetiology [12]. To note, systematic screening for tuberculosis is needed in our institute to rule it out in case of suspicion.

2. Lung metastases

In light of two randomized phase II trials available, patients with synchronous oligometastatic or oligopersistent cancer can benefit from curative treatment at least once disease has stabilized with initial systemic therapy [13,14]. At our institute, SBRT is indicated for patients presenting with oligometastatic lung disease (1–5 metastatic sites) [15], measuring less than 5cm in size, with slow growth and whose primary tumour is controlled [16].

II. Treatment conditions

Eligibility for SBRT requires a certain set of conditions. A complete and recent radiological workup (= 4 weeks) with a thoracic CT and a PET-CT is required for optimum disease staging. Targeted lesions cannot exceed 5 cm in size [12]. While SBRT is feasible for tumours > 5 cm, low quality of evidence limits its use in this case [17]. Patients need to have a KPS (Karnofsky Performance Score) of at least 70, and with no contraindication to supine position. Special considerations are taken into account in the case of patients with cardiac implantable electronic device [18]. In case of altered pulmonary function or pre-existing pulmonary fibrosis, the decision is made during the RT board meeting for a less hypo-fractionated SBRT and adaptation of dosimetric constraints.

III. Prescription dose and fractionation

There is no single standard scheme for all tumour presentations. Published data generally reflect the experience of individual institutions, which to some extent explains inter-institutional differences in total dose, fractionation schedule, total treatment time, and dose delivery technique. These differences make it difficult to standardize dosing regimens and dosimetry specifications when administering SBRT. However, the recommended fractionation regimens are all equivalent to a minimum BED (Biological effective Dose) of 100 Gy. In fact, local control is significantly improved with a BED >100Gy [19] and BED at the peripheral tumour margin was found to be the strongest predictor of local control [20]. As per the ESTRO and ACROP recommendations [11], we aimed to set up risk-adapted fractionation regimens according to the location of the tumour, with 48h in-between fractions. Four main locations were defined in Table 1. Some tumours might be “too central” to be safely treated with SBRT when applying a BED10 >100 Gy. These are called ‘hyper-central’ tumours and they extend directly to the bronchial tree or critical mediastinal structures. In this case, an 8-fraction regimen results in high risk of grade 3 to 5 toxicities as well as treatment-related death, and thus a more fractionated schedule is recommended [21].