Question 1

What are the complications of stereotactic radiotherapy (SRT/SRS), and what is the prognosis?

Dr. Garima Singh · Accepted Answer

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.

Question 2

What has been your experience treating pediatric cancer patients?

Dr. Garima Singh · Accepted Answer

I have treated around ten pediatric patients from Ethiopia specifically, as part of a broader pediatric caseload. Pediatric malignancy needs to be treated very carefully. In medulloblastoma, for example, craniospinal irradiation planning has to be extremely precise to prevent radiation-related toxicity. Because survival in cancers like ependymoma and medulloblastoma is often good, the most important concern becomes preventing secondary malignancy later in life, which means paying close attention to low-dose spillage, or integral dose, across the whole treatment field. For pediatric cases needing long treatment fields, we generally use tomotherapy, and we get very good outcomes.

Question 3

When is radiotherapy a viable treatment option for a patient, and when is it not?

Dr. Garima Singh · Accepted Answer

It depends on the site and the stage. In early-stage head and neck cancer, surgery alone can be sufficient, but high-risk features can still call for adjuvant radiotherapy. In locally advanced disease, radiotherapy is needed. In stage IV disease, the role of radiotherapy is palliative: relieving symptoms such as pain, bleeding, cord compression or hemoptysis, to improve quality of life. More than 50 to 60 percent of patients need radiotherapy at some point, whether as radical treatment, adjuvant therapy or palliation, and we rely on a multidisciplinary tumour board to decide the exact timing for each patient.

Question 4

What is the guiding principle for when to integrate chemotherapy with radiotherapy, versus using either alone?

Dr. Garima Singh · Accepted Answer

We follow international guidelines. Using cervical cancer as an example: stage IA, IB1, IB2 and IIA1 disease is treated with surgery first. Adjuvant treatment then depends on the Peters and Sedlis criteria: positive margins, positive nodes or parametrial involvement call for concurrent chemoradiation; intermediate-risk combinations of deep stromal invasion, tumour size and lymphovascular space invasion, such as lymphovascular invasion with deep stromal invasion, or a tumour over 4 centimetres with deep stromal invasion, call for radiation alone; if those criteria are not met, no adjuvant treatment is needed and the patient goes to follow-up. Locally advanced disease, stage IB3 to IVA, needs concurrent chemoradiation, and a bulky tumour or high nodal burden may call for six weeks of induction chemotherapy before it. Stage IVB generally starts with chemotherapy. Every site, endometrium, lung, breast, has its own guideline, and we make these calls through tumour board discussion.

Question 5

Does imaging or histopathological cell type weigh more heavily in this decision?

Dr. Garima Singh · Accepted Answer

Staging starts with clinical examination. If the tumour is localised to the cervix, with no fornix or parametrial involvement and a size under 4 centimetres, it can be operated on. MRI is then needed to check for parametrial invasion; if MRI shows no parametrial involvement and a free vagina, the patient can be operated on. This is a clinico-radiological diagnosis, and it guides the proper optimisation of treatment. The stepwise approach matters because it decreases toxicity: if a bulky tumour, such as stage IB3, is operated on upfront, it is difficult to remove with negative margins, and there is a risk of high-risk features such as a positive margin after surgery.

Question 6

Is there a role for radioactive bead implantation in this therapy, for example in cervical cancer?

Dr. Garima Singh · Accepted Answer

That is brachytherapy, which I covered in the lecture. When brachytherapy was first developed for carcinoma cervix, it used preloaded sources: the source had to be implanted inside the tumour. The technology has since evolved to after-loading. We apply the Fletcher-Suit applicator, and the machine then transfers the radioactive source into the tandem. We now practise after-loading brachytherapy.

Question 7

What are the current dose constraints for organs at risk in head and neck cancer?

Dr. Garima Singh · Accepted Answer

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.

Question 8

What is the role of SBRT in early-stage lung and prostate cancer?

Dr. Garima Singh · Accepted Answer

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.

Live Discussion with Dr. Garima Singh