In the dynamic world of oncology, where every advancement brings us a step closer to defeating cancer, Nuclear Medicine and Theranostics stand as beacons of transformative change. These fields are not only redefining diagnostic accuracy but are also tailoring therapies for patients with unmatched precision. From early detection to advanced treatment, nuclear medicine is playing a pivotal role in reshaping modern cancer care.

The Rise of Nuclear Medicine in Oncology

Nuclear medicine utilises small amounts of radioactive materials known as radiopharmaceuticals to diagnose and treat diseases. Unlike conventional imaging, which often captures structural changes, nuclear medicine imaging evaluates physiological and molecular functions, often revealing disease much earlier.

One of the biggest milestones in oncology was the introduction of PET/CT, particularly with fluorodeoxyglucose (FDG). FDG PET/CT has revolutionised cancer imaging by detecting increased glucose metabolism typical of malignancies. This modality plays a critical role as a single-stop imaging solution, all along the journey of a patient’s treatment of cancer and subsequent follow-up. State-of-the-art modern-day oncology cannot be envisaged without access to Nuclear Medicine services, especially PET/CT services.

The major indications for PET/CT in oncology are:

• Lesion characterisation and guiding biopsy – In a case of a mass lesion with suspected malignant aetiology, before biopsy, FDG PET/CT may be done to know the nature of the lesion (benign vs. malignant) and to identify the most accessible site to biopsy. For example, a brain lesion might be a metastasis from an occult breast or lung primary or could be a primary brain tumour. FDG PET/CT in this setting helps to understand if it’s a primary brain lesion or it’s a brain metastasis from a primary elsewhere in the body and thus guides the most accessible and representative site for biopsy.

• Initial staging - In a newly diagnosed case of cancer, FDG PET/CT is done to know if the cancer is restricted to the primary site or has spread to other parts of the body. This is very important, as one of the most important factors that determine the treatment and outcomes of the treatment is the initial stage of the cancer.

• Restaging - Primary surgery has been done for a mass (for example: in the breast) and the final biopsy comes out as cancer. In this situation, FDG PET/CT is again important to assess if the cancer has already spread to other parts of the body or not, as further management depends on it.

• Assessment of response to treatment - A patient undergoing cancer treatment (chemotherapy / immunotherapy / molecular therapies) needs to know how he/she is responding to the ongoing treatment, which is objectively depicted with a response evaluation FDG PET/CT scan. The presence of a baseline FDG PET/CT scan in this setting enhances the effectiveness of a response assessment PET/CT scan.

• RT Planning - FDG PET/CT enhances the effectiveness of accurate radiotherapy planning compared to conventional imaging.

• Recurrence / Suspected Recurrence Evaluation - A treated case of cancer on follow-up, showing either clinical or biochemical (rising tumour markers) suspicion of recurrence, FDG PET/CT solves this clinical dilemma with its ability to find out if there is any true disease recurrence as such and if so which all parts of the body /organs which are involved in the disease recurrence. Further treatment would be tailored accordingly.

Nuclear medicine has also expanded into targeted diagnostics using radio-labelled peptides and antibodies. A significant example is the use of Gallium-68 (68Ga) DOTATATE PET/CT for neuroendocrine tumours, providing both sensitivity and specificity that far surpass conventional scans. Other radiopharmaceuticals of importance in routine oncology practice include 68Ga PSMA PET/CT for prostate cancer imaging, 68Ga Exendin IV PET/CT for imaging Insulinomas, 18F-FDOPA and 18F-FET PET/CT for brain tumour imaging, etc.

Theranostics: The Fusion of Diagnosis and Therapy

Theranostics - the convergence of therapy and diagnostics - embodies the core philosophy of personalised medicine. It involves using the same molecular target for both imaging and treatment. This ensures that only those patients likely to benefit from therapy are selected, minimising toxicity and maximising the effectiveness of the therapy.

A prime example is Lutetium-177 (177Lu) DOTATATE therapy for neuroendocrine tumours. Patients undergo imaging with 68Ga DOTATATE to assess receptor expression. If positive, they are treated with Lutetium-177 (177Lu) DOTATATE, which binds to the same receptors and delivers targeted beta radiation to tumour cells.

In prostate cancer, PSMA-based theranostics have reshaped the landscape. Gallium-68 PSMA PET/CT enables high-resolution imaging of metastatic disease, and Lutetium-177 PSMA therapy provides effective treatment even in castration-resistant stages. This approach offers improved survival and quality of life for many patients.

Changing the Way Modern Oncology is Practised

Nuclear medicine and theranostics have significantly influenced cancer care in the following ways:

• Earlier Detection - Nuclear medicine imaging often detects tumours before anatomical imaging, allowing early diagnosis and potentially curative interventions.

• Treatment Personalisation - Theranostics enables a “see and treat” strategy, ensuring the treatment is suited to the molecular profile of the tumour.

• Non-Invasive Disease Monitoring - PET/CT allows real-time tracking of disease progression or regression, eliminating the need for repeated biopsies.

• Better Outcomes with Fewer Side Effects - Targeted radiotherapy reduces damage to healthy tissues, resulting in fewer systemic side effects compared to chemotherapy.

• Cost-Efficiency in the Long Term - While nuclear medicine may appear expensive when considering the cost of the scan alone, it is in fact the most cost-effective single-stop imaging solution in oncology, as it reduces the need for ineffective therapies and prolonged hospitalisations.

The Road Ahead: What the Future Holds

As science and technology evolve, the future of nuclear medicine and theranostics looks more promising than ever.

Alpha-Emitter Therapies: "The nuclear bomb" inside the cell

Alpha particles deliver high-energy radiation over short distances, causing lethal double-strand DNA breaks in cancer cells. This also gives an inherent advantage of not affecting innocent nearby non-malignant cells, thereby reducing adverse effects to adjoining normal tissues. Agents like Actinium-225 PSMA are showing exceptional promise in resistant prostate cancer with fewer side effects.

New Molecular Targets

Theranostic agents are being developed for other cancers such as breast (HER2-targeted), pancreatic (CA19-9), glioblastoma (EGFR), and haematologic malignancies. These advancements will broaden the application of theranostics beyond neuroendocrine and prostate cancers.

Integration with Immunotherapy

Radiation from theranostic agents can trigger immunogenic cell death, making cancer cells more visible to the immune system. Combining theranostics with checkpoint inhibitors is being explored in clinical trials.

Role of Artificial Intelligence

AI is being used to interpret complex imaging data, detect subtle lesions, predict patient outcomes, and even guide radiopharmaceutical dosing.

Paediatric Applications

Radio-Theranostics are being cautiously explored in children with cancers like neuroblastoma and medulloblastoma, aiming for high efficacy with minimal long-term toxicity.

Overcoming Challenges

While the outlook is optimistic, several challenges must be addressed to achieve widespread adoption:

• High Costs and Infrastructure Needs: Setting up cyclotrons, PET/CT centres, and radio-pharmacies requires significant investment. It may not be a cost-effective or viable option for all hospitals or cancer treatment facilities to set up their own nuclear medicine facility. The most cost-effective option is to utilise the services of stand-alone Nuclear Medicine centres by effectively collaborating with them.

  
  

• Regulatory Barriers: Radiopharmaceuticals must undergo rigorous safety and efficacy evaluations.

  
  

• Training and Awareness: Nuclear medicine professionals, oncologists, and primary care providers must work collaboratively and remain updated.

  
  

• Access in Low-Resource Settings: International cooperation and government funding are essential to make these technologies accessible to all.

Conclusion

Nuclear medicine and theranostics are no longer futuristic ideas—they are today's reality and tomorrow's standard of care. They embody the transition from generalised treatments to precision oncology, where treatments are tailored, effective, and kinder to patients.

The journey ahead involves innovation, collaboration, and education. As we invest in infrastructure, train specialists, and support research, we bring ourselves closer to a future where cancer is not feared—but managed, treated, and eventually cured with accuracy and compassion.

Let us embrace this nuclear revolution in cancer care and drive it forward—for our patients, our healthcare systems, and the future of medicine.