Theranostics

Overview

Theranostics, also called Radiotheranostics, is an advanced area of Nuclear Medicine that combines targeted diagnosis and targeted treatment in one personalised approach. It uses radioactive medicines, known as radiopharmaceuticals, to first identify disease at the molecular level and then treat selected patients using a related therapeutic radiopharmaceutical.

Theranostics is most commonly used in certain cancers, such as neuroendocrine tumours and advanced prostate cancer. It helps doctors choose patients who are more likely to benefit from treatment, deliver radiation more precisely to diseased cells, and monitor response over time.

What Is Theranostics?

Theranostics combines two steps: diagnostic imaging and therapy. In the diagnostic step, a small amount of radiotracer is used, usually with PET/CT or SPECT/CT imaging, to show whether cancer cells carry a specific target. If the scan confirms that the target is present, a similar therapeutic radiopharmaceutical may be used to deliver radiation directly to those cells.

Common examples include:

• PSMA PET imaging and PSMA-targeted therapy for prostate cancer

• Somatostatin receptor imaging and peptide receptor radionuclide therapy, also called PRRT, for neuroendocrine tumours

• Radioiodine imaging and therapy for selected thyroid diseases

• Bone-targeted radiopharmaceutical therapy in selected metastatic bone disease

• Emerging theranostic approaches for other cancers in specialised centres

The goal is to match the right treatment to the right patient based on the biology of the disease.

Causes and Risk Factors

Theranostics may be considered when a disease has a specific molecular target that can be detected by nuclear medicine imaging and treated with a related radiopharmaceutical.

Patients may be evaluated for theranostics in conditions such as:

• Metastatic prostate cancer

• Neuroendocrine tumours

• Differentiated thyroid cancer

• Selected bone metastases

• Recurrent or advanced cancers where standard treatment options are limited

• Cancers requiring molecular imaging for staging or treatment planning

• Disease that shows suitable uptake on diagnostic PET/CT or SPECT/CT scans

Suitability depends on cancer type, disease stage, previous treatments, organ function, blood counts, scan findings, and overall health.

Symptoms

Theranostics is not usually recommended based on symptoms alone. It is considered after a confirmed diagnosis and specialist evaluation. Symptoms depend on the underlying cancer or disease being treated.

Patients being evaluated may have:

• Known cancer with suspected spread or recurrence

• Rising tumour markers despite treatment

• Bone pain from metastatic disease

• Unexplained weight loss or fatigue

• Hormonal symptoms in neuroendocrine tumours, such as flushing or diarrhoea

• Symptoms related to prostate, thyroid, or other cancer progression

• Imaging findings that need molecular characterisation

Urgent medical care is needed for severe pain, spinal cord compression symptoms, difficulty breathing, confusion, severe dehydration, uncontrolled vomiting, or sudden neurological weakness.

Diagnosis

Diagnosis and treatment planning require close coordination between nuclear medicine physicians, oncologists, radiologists, medical physicists, and other specialists.

Common diagnostic steps include:

• Review of cancer diagnosis, stage, and previous treatment

• PET/CT or SPECT/CT using a target-specific radiotracer

• Blood tests for kidney function, liver function, blood counts, and relevant tumour markers

• Assessment of bone marrow reserve and organ function

• Review of CT, MRI, biopsy, or pathology reports

• Evaluation of treatment eligibility and expected benefit

• Radiation safety counselling before therapy

• Dosimetry planning in selected cases to estimate radiation dose to tumour and normal organs

The diagnostic scan is important because it helps confirm whether the disease is likely to respond to the matching therapy.

Treatment Options

Treatment depends on the type of disease, radiotracer uptake, prior therapies, and patient fitness.

Theranostic treatment may include:

• Radioligand therapy for selected prostate cancer patients

• PRRT for selected neuroendocrine tumour patients

• Radioiodine therapy for selected thyroid conditions

• Bone-seeking radiopharmaceutical therapy for selected painful bone metastases

• Combination treatment with oncology therapies when appropriate

• Symptom management and supportive care

• Monitoring scans and blood tests after treatment

• Repeat treatment cycles based on response and safety

Therapy is usually given through an IV injection or oral radioactive iodine, depending on the treatment type. After treatment, patients receive radiation safety instructions to protect family members, caregivers, and the public.

Prevention and Outlook

Theranostics does not prevent cancer, but it can help personalise treatment and avoid ineffective therapy in patients whose scans do not show the required target. It also allows doctors to monitor treatment response and adjust care more precisely.

The outlook depends on cancer type, tumour burden, radiotracer uptake, organ function, previous treatments, and response to therapy. In suitable patients, theranostics can improve disease control, reduce symptoms, and support a more personalised cancer treatment pathway. It should be offered in centres with trained nuclear medicine teams, radiation safety systems, and multidisciplinary oncology support.

Frequently Asked Questions

1. What does theranostics mean?
   Theranostics combines “therapy” and “diagnostics.” It uses one targeted radiopharmaceutical for imaging and a related one for treatment.

2. Is theranostics the same as chemotherapy?
   No. Chemotherapy uses medicines that affect rapidly dividing cells throughout the body. Theranostics uses targeted radioactive medicines designed to bind to specific disease cells.

3. Which cancers are commonly treated with theranostics?
   It is commonly used for selected neuroendocrine tumours, advanced prostate cancer, thyroid cancer, and certain cases of metastatic bone disease.

4. Is radiotheranostics safe?
   It is generally safe when patients are carefully selected and treated by trained specialists. Side effects depend on the treatment and may include fatigue, nausea, dry mouth, low blood counts, or kidney-related concerns in selected cases.

5. Why is a PET/CT scan needed before therapy?
   The scan checks whether the cancer cells have the target needed for the treatment to work. If uptake is low or absent, the therapy may not be suitable.

6. Will I be radioactive after treatment?
   For a short time, yes. The care team will give specific instructions about distance, hygiene, travel, contact with children or pregnant people, and follow-up based on the radiopharmaceutical used.