Stereotactic Radiosurgery and SBRT: High-Precision Treatment for Brain and Body

They are complementary, not competing. Staging starts with clinical examination: if the tumour looks confined to the cervix, with no fornix or parametrial involvement and a size under 4 centimetres, surgery looks feasible on clinical grounds. MRI is then used specifically to confirm there is no parametrial invasion, which gives us a clinico-radiological diagnosis. Only after surgery does histopathology decide whether adjuvant treatment is needed. This stepwise approach, clinical exam, then imaging, then surgery, then histopathology, is important because operating on an advanced or bulky tumour without confirming operability first raises the risk of a positive margin, which then commits the patient to more aggressive treatment than necessary.

Yes, that is brachytherapy. Historically, cervical cancer brachytherapy used preloaded sources, meaning the source had to be implanted directly. Technology has evolved to after-loading systems: the applicator, such as the Fletcher-Suit system, is placed first, and the radioactive source is then transferred into the tandem remotely through the treatment machine. That shift from preloading to after-loading has improved safety for patients and staff.

It depends on the treatment area. For oral cavity cancers such as carcinoma of the tongue, the parotid and submandibular glands, buccal mucosa and dysphagia-related structures are the relevant organs at risk. We keep parotid gland mean dose below 26 Gy, and esophagus and trachea mean dose below 45 Gy. Buccal mucosa constraints are not as robustly established in the literature, but our institute's practice is to keep dose there within about 32 to 35 Gy without compromising target coverage, and to keep overall oral cavity dose below 45 Gy. We follow RTOG, QUANTEC, Timmerman, and more recently HyTEC and PENTEC guidelines for these constraints.

For lung cancer, if the patient is operable, surgery is the treatment of choice. If a patient is medically inoperable due to comorbidity, we give SBRT, whether it is a primary early-stage lung cancer or a lung metastasis from elsewhere, such as breast cancer. Dose depends on tumour location: ultracentral tumours, close to the heart or mediastinum, get a more cautious regimen of around 60 to 70 Gy in 7 to 10 fractions; peripheral tumours can get 50 Gy in 5 fractions, or sometimes 55 Gy in 5 fractions. We follow established SBRT dose-constraint guidelines for all of this.

It depends heavily on where the tumour sits. In fractionated radiosurgery for brain tumours, the incidence of radiation necrosis runs below 10 percent, and brain edema is another recognised complication. Risk rises when the target is near a critical structure such as the motor cortex or brainstem; robust dosing data for the motor cortex are limited, but the working figure for a single SRS session is around 15 Gy to that structure. With fractionated SRT or SRS, clinicians have to be especially vigilant about the proximity of organs at risk during planning. Done with that vigilance, SRS can be delivered safely to metastatic brain lesions with minimal complications, though it demands real expertise and careful dose painting.

SRS is defined by a specific dosing logic: a very high dose per fraction, greater than 5 Gy, delivered in fewer than five sessions.

SRS is also used for benign tumors such as meningioma, pituitary tumors and acoustic neuroma, recurrent gliomas, vascular malformations such as arteriovenous malformations, and trigeminal neuralgia, with selected use in epilepsy and ocular malignancies such as uveal melanoma.

Both can be delivered on a range of platforms, including conventional linear accelerators, tomotherapy systems, Gamma Knife, CyberKnife and proton therapy systems.

In one case, SRS delivered over three sessions produced complete radiological resolution of a metastatic brain lesion at follow-up.

Prostate cancer's low alpha-beta ratio makes it particularly responsive to hypofractionated, high-dose-per-fraction schedules, though careful patient selection and strict adherence to dose constraints are what make the approach safe.