Last reviewed by Dr. Dharmender Malik on 14 May 2026 · this article reflects the published primary literature and current clinical practice at FMRI Gurugram.
Introduction
Nuclear medicine is the medical speciality that uses small amounts of radioactive material to both see disease and to treat it. Unlike X-rays and CT — which produce images by passing radiation through the body from outside — nuclear medicine works from the inside out: a radioactive molecule is given to the patient (intravenously, orally, or by injection), travels to its biological target, and either emits signals that imaging cameras detect, or delivers radiation directly to disease tissue. This article is a patient-level pillar guide to how nuclear medicine fits into modern cancer care: what radiopharmaceuticals are, the difference between PET and SPECT imaging, the principle of theranostics, and where each established radiopharmaceutical sits in the cancer treatment sequence. Every clinical claim traces to a peer-reviewed publication, regulatory filing, or guideline statement.
What nuclear medicine actually is
AI Overview · short answer
Nuclear medicine is a medical speciality that uses radioactive substances called radiopharmaceuticals for diagnosis and treatment of disease[1]. In cancer care, it serves two distinct functions: imaging (PET-CT and SPECT-CT scans that map biological processes such as glucose metabolism, somatostatin receptor expression, or PSMA expression) and therapy (radiopharmaceuticals that deliver targeted radiation directly to tumour cells)[2]. The principle of theranostics — using a diagnostic imaging agent to confirm the presence of a target, then using a matched therapeutic agent that binds the same target — has driven the recent expansion of the field, with FDA-approved Lu-177 PSMA-617 (Pluvicto, 2022) for metastatic prostate cancer and Lu-177 DOTATATE (Lutathera, 2018) for neuroendocrine tumours as landmark examples[3][4].
Nuclear medicine differs from conventional radiology (X-ray, CT, MRI, ultrasound) in three structural ways[1]:
- The radiation comes from inside the body, not from outside. The patient is given a radioactive molecule (a radiopharmaceutical). The radiation source is wherever that molecule ends up — in tumour, in normal organ, or in elimination pathways.
- It images function, not just anatomy. CT and MRI primarily show shape, size, density, and edges. Nuclear medicine shows biological process — what is metabolically active, what binds a receptor, what concentrates a peptide. The same anatomical structure can look identical on CT and very different on PET, because the question being asked is different.
- The same target principle drives both diagnosis and treatment. A molecule that binds a tumour marker for imaging — for example DOTATATE binding somatostatin receptor 2 — can be paired with a different radionuclide on the same molecule to deliver therapeutic radiation to the same target. This pairing is the core of theranostics.
The radioactive isotopes used in nuclear medicine vary in physical properties (half-life, type of radiation emitted, energy) and these properties determine whether an isotope is suitable for imaging (typically gamma or positron emission, short range) or for therapy (typically beta or alpha emission, short range to tumour but high local energy deposition)[5].
PET imaging vs SPECT imaging — the two main scanner types
Nuclear medicine imaging in cancer uses two principal scanner modalities, distinguished by the type of radiation the radiopharmaceutical emits[6]:
| Modality | Radiation detected | Resolution | Common cancer agents |
|---|
| PET-CT (Positron Emission Tomography with CT) | Pairs of 511 keV photons from positron annihilation | ~4-5 mm typical clinical | F-18 FDG, Ga-68 PSMA, F-18 PSMA, Ga-68 DOTATATE, F-18 DOTATATE, F-18 fluciclovine, F-18 sodium fluoride |
| SPECT-CT (Single Photon Emission Computed Tomography with CT) | Single gamma photons emitted directly by the radionuclide | ~10-15 mm typical clinical | Tc-99m MDP (bone scan), Tc-99m sestamibi, I-123 / I-131 (thyroid), In-111 / Tc-99m DTPA, Lu-177 SPECT (post-therapy) |
PET-CT generally provides higher resolution and more quantitative data than SPECT-CT but requires positron-emitting isotopes which are typically cyclotron- or generator-produced (more expensive, shorter half-life logistics). SPECT-CT uses gamma-emitters that are more widely available and is established in routine cancer practice for bone scans, thyroid scans, and post-radioligand-therapy distribution imaging[7].
Both modalities now use hybrid scanners that combine the functional nuclear medicine image with a low-dose CT scan acquired in the same session, providing simultaneous functional and anatomical information.
FDG PET-CT — the workhorse of cancer imaging
F-18 fluorodeoxyglucose (FDG) PET-CT is the most widely used PET imaging agent in oncology. FDG is a glucose analogue: cancer cells, which typically have increased glucose uptake (the Warburg effect), accumulate FDG preferentially relative to most normal tissues[8]. FDG PET-CT is established in routine cancer practice for:
- Staging at diagnosis for many cancer types — lymphoma, oesophageal, head and neck, lung, melanoma, and others.
- Response assessment after chemotherapy or radiation, using established criteria such as Deauville score for lymphoma or PERCIST for solid tumours.
- Restaging when cancer markers rise or imaging is suspicious for recurrence.
- Detection of unknown primary in patients presenting with metastatic disease of unknown origin.
FDG is not specific to cancer — it accumulates in any tissue with high glucose turnover including inflammation, infection, brown fat, and active muscle. Interpretation requires expert reading of the functional image alongside the anatomical CT. Not all cancers are FDG-avid: well-differentiated neuroendocrine tumours, low-grade prostate cancer, and some renal carcinomas typically show low FDG uptake, and other tracers (Ga-68 DOTATATE, Ga-68 PSMA, etc.) are used in those contexts[9].
Receptor-targeted PET imaging — Ga-68 PSMA, Ga-68 DOTATATE, and more
Beyond FDG, modern cancer imaging uses a growing suite of receptor-targeted PET radiopharmaceuticals. Each is built on the same architecture — a small targeting molecule that binds a tumour marker, linked to a positron-emitting isotope[10]:
- Ga-68 PSMA-11 / F-18 PSMA — binds prostate-specific membrane antigen (PSMA) on prostate cancer cells. Has replaced bone scan and CT as primary staging modality for high-risk localised prostate cancer and biochemical recurrence (per the proPSMA, OSPREY, and CONDOR trials). FDA-approved for these indications.
- Ga-68 DOTATATE / Ga-68 DOTATOC / F-18 DOTATATE — binds somatostatin receptor 2 (SSTR2) on neuroendocrine tumour cells. Replaced In-111 OctreoScan SPECT in modern practice and is the eligibility scan for Lu-177 DOTATATE PRRT.
- F-18 fluciclovine — synthetic amino acid; FDA-approved for prostate cancer recurrence localisation.
- F-18 sodium fluoride — bone-seeking agent for skeletal metastasis evaluation; higher sensitivity than Tc-99m MDP bone scan for many indications.
- Ga-68 FAPI — fibroblast activation protein inhibitor; emerging tracer for stromal-rich cancers; investigational in most jurisdictions.
Each of these radiopharmaceuticals exists because conventional imaging (CT, MRI) cannot reliably detect or characterise the relevant disease — they fill specific gaps in the cancer-imaging pathway[11].
The theranostic principle — same target, two roles
The defining advance in nuclear medicine over the past decade is the consolidation of the theranostic principle: a single biological target (a receptor or antigen) is addressed by paired imaging and therapy agents that share the same targeting molecule but carry different radionuclides[3]:
| Target | Diagnostic agent (imaging) | Therapeutic agent (treatment) | Approved indication |
|---|
| Somatostatin receptor 2 (SSTR2) | Ga-68 DOTATATE | Lu-177 DOTATATE (Lutathera) | Gastroenteropancreatic NETs (FDA 2018, EMA 2017, label expanded 2024 with NETTER-2) |
| Prostate-specific membrane antigen (PSMA) | Ga-68 PSMA-11, F-18 PSMA-1007 | Lu-177 PSMA-617 (Pluvicto) | Metastatic castration-resistant prostate cancer (FDA 2022, EMA 2023, label expanded 2025 with PSMAfore) |
| Iodine uptake (sodium-iodide symporter) | I-123, I-131 diagnostic dose | I-131 therapeutic dose | Differentiated thyroid cancer, hyperthyroidism — decades-established |
| Bone matrix (hydroxyapatite) | Tc-99m MDP bone scan, F-18 NaF PET | Ra-223 dichloride (Xofigo) | Symptomatic bone-metastatic CRPC (FDA 2013, EMA 2013) |
| Liver arterial supply | Tc-99m MAA SPECT (mapping) | Y-90 microspheres (TheraSphere, SIR-Spheres) | HCC and metastatic liver disease (FDA/EMA approved) |
The clinical advantage of the theranostic pairing is patient selection: the imaging scan confirms that the disease expresses the target at sufficient intensity for the therapy to be effective. A patient with PSMA-negative prostate cancer on Ga-68 PSMA PET is unlikely to benefit from Lu-177 PSMA therapy — and the scan-then-treat sequence allows that decision to be made before therapy commits. For more on PSMA expression specifically see our companion PSMA expression article.
Lu-177 radioligand therapy — PSMA and DOTATATE
Lutetium-177 (Lu-177) is the most widely used therapeutic radionuclide in modern radioligand therapy. Its physical properties make it well-suited for the role[12]:
- Beta-emitter with mean range in tissue of ~0.7 mm (effective tumour kill at the receptor-positive cell level)
- Half-life 6.65 days (long enough to circulate, bind, and deliver dose; short enough that radiation safety is manageable)
- Low-yield gamma emission (113 keV, 208 keV) allows post-therapy SPECT imaging to confirm intended distribution
- Available from both indigenous Indian production (BRIT) and international manufacturers
Two Lu-177-based therapies are currently FDA / EMA approved:
- Lu-177 PSMA-617 (Pluvicto) — for PSMA-positive metastatic castration-resistant prostate cancer based on the VISION trial: median radiographic PFS 8.7 vs 3.4 months (HR 0.40), median OS 15.3 vs 11.3 months (HR 0.62), FDA-approved 2022, EMA-approved 2023, label expanded 2025 with the PSMAfore trial supporting use in pre-chemotherapy mCRPC[13].
- Lu-177 DOTATATE (Lutathera) — for somatostatin receptor-positive gastroenteropancreatic NETs based on NETTER-1 (PFS HR 0.21) and NETTER-2 (median PFS 22.8 vs 8.5 months, HR 0.276, leading to 2024 first-line label expansion in grade 2/3 GEP-NETs)[4][14].
For deeper coverage see our companion articles on Lu-177 PSMA outcomes and PRRT for NETs.
Y-90 radioembolization for liver malignancies
Yttrium-90 (Y-90) transarterial radioembolization (TARE) is a different category of nuclear medicine therapy: rather than systemically targeting a receptor, Y-90-loaded microspheres are infused directly into the hepatic arterial supply of liver tumours, where they lodge in the microvasculature and deliver short-range beta radiation to the tumour[15]:
- Y-90 — pure beta-emitter, mean range in tissue ~2.5 mm, half-life 2.67 days. Higher energy than Lu-177; well-suited to the locoregional delivery model.
- Indications — hepatocellular carcinoma (including as bridge to transplant — see our TARE bridge-to-transplant article), liver-dominant metastatic colorectal cancer, neuroendocrine liver metastases.
- Pre-treatment workup — multiphasic imaging, mapping angiography, Tc-99m MAA SPECT/CT for lung-shunt fraction and tumour distribution, personalised dosimetry planning (DOSISPHERE-01 principle).
- Evidence base — LEGACY (88% ORR in solitary HCC ≤8 cm with radiation segmentectomy), DOSISPHERE-01 (personalised vs standard dosimetry, OS 26.6 vs 10.7 months), PREMIERE (TARE longer time-to-progression than TACE in HCC).
For the full mechanism and indications review see our Use of Y-90 article.
Established radiopharmaceuticals — I-131 and Ra-223
Two further radiopharmaceuticals are well-established in cancer treatment with decades of clinical experience[16][17]:
- I-131 (iodine-131) — the oldest established radiotherapeutic in oncology, used since the 1940s. Beta-emitter (half-life 8 days). For differentiated thyroid cancer (papillary, follicular), I-131 is used after total thyroidectomy to ablate thyroid remnant and treat residual or metastatic disease. The sodium-iodide symporter (NIS) on thyroid cells provides the targeting mechanism — no separate targeting molecule is needed. ATA, NCCN, and ESMO guidelines provide indications.
- Ra-223 (radium-223 dichloride, Xofigo) — alpha-emitter (half-life 11.4 days) approved by FDA (2013) and EMA (2013) for symptomatic bone-metastatic CRPC based on the ALSYMPCA trial. Ra-223 is a calcium mimetic — it concentrates in bone matrix at sites of high turnover (typical of bone metastases) and delivers alpha radiation locally. Median overall survival benefit 3.6 months (HR 0.70) vs placebo in ALSYMPCA. Six monthly infusions are standard.
Where nuclear medicine fits alongside surgery, radiotherapy, chemotherapy, and targeted therapy
Nuclear medicine therapy does not exist in isolation. It sits within the broader cancer-treatment ecosystem and is typically applied in specific situations[18]:
| Modality | Where it leads | Where nuclear medicine adds value |
|---|
| Surgery | Curative-intent for localised disease (resectable HCC, localised prostate cancer, resectable NETs) | Imaging supports staging; therapy generally not at this stage except adjuvant I-131 for thyroid cancer |
| External-beam radiotherapy | Localised or oligometastatic disease; some palliative settings | Complementary: nuclear medicine adds systemic radiotherapy where external beam cannot reach all sites; FDG PET supports radiotherapy planning |
| Chemotherapy | Systemic disease across most cancers | Imaging supports response assessment; therapy used when chemotherapy options exhausted or when toxicity profile favours radioligand therapy |
| Targeted therapy (small molecule, monoclonal antibody) | Selected biomarker-positive disease (e.g., EGFR, HER2, BRAF, immune-checkpoint, AR-pathway) | Nuclear medicine targets different biology (receptor density, metabolic pathway) — frequently complementary rather than competing |
| Hormone therapy | Hormone-driven disease (prostate, breast, NETs) | Established combinations: Lu-177 DOTATATE plus octreotide; Lu-177 PSMA plus ARPI (under emerging evidence) |
| Immunotherapy | Many solid tumours and lymphomas | FDG PET supports response assessment (iRECIST); combinations of radioligand therapy with immunotherapy under active investigation |
The decisions about sequence and combination are made at multidisciplinary tumour board review, taking into account disease biology, prior treatment exposure, organ reserve, performance status, and patient preferences[19].
Safety, radiation, and side effects
Nuclear medicine involves radiation exposure, and the safety profile is one of the most-asked questions by patients. Three points are central[20]:
- Imaging exposure — typical FDG PET-CT delivers an effective dose of approximately 5-10 mSv, similar to or slightly more than a diagnostic CT scan. The radiation exposure is justified by the diagnostic information gained and is regulated under AERB norms in India and equivalent regulators internationally.
- Therapy exposure — the patient is the radiation source for days to weeks after Lu-177, Y-90, I-131, or Ra-223 administration. Discharge instructions cover distance from family, sleeping arrangements, bathroom use, and contact with pregnant women and young children. The duration of these precautions depends on the radionuclide and the cumulative activity.
- Therapy side effects — vary by therapy. Common across radioligand therapy: fatigue, mild nausea, mild cytopenia. Specific to each: dry mouth (Lu-177 PSMA), amino-acid infusion nausea (Lu-177 DOTATATE), post-embolization syndrome (Y-90 TARE), neck swelling (I-131 thyroid ablation), bone pain flare (Ra-223). Long-term risks include therapy-related myeloid neoplasm in cumulative-exposure cohorts.
For detailed cross-therapy side-effect coverage see our side effects of nuclear medicine treatment article.
Regulatory framework — how nuclear medicine is governed in India
Nuclear medicine in India operates under a multi-layered regulatory framework. Understanding this framework is part of informed consent for any nuclear medicine procedure[21]:
- Atomic Energy Regulatory Board (AERB) — issues licences for medical use of radioactive substances. Applicable safety code is AERB/RF-MED/SC-2 (Rev. 2) for nuclear medicine facilities; every authorised centre operates under specific licence conditions covering radiation safety, personnel qualification, and quality assurance.
- Drug Controller General of India (DCGI / CDSCO) — regulates the radiopharmaceuticals themselves under the Drugs and Cosmetics Act, including import permissions and Good Manufacturing Practice oversight.
- Board of Radiation and Isotope Technology (BRIT) — Department of Atomic Energy-affiliated indigenous producer of Lu-177 and other medical radioisotopes.
- Indian College of Nuclear Medicine — professional society aligned with EANM and SNMMI procedure guidelines.
For an international patient context, the Indian regulatory framework is closely aligned with EANM (European) procedure guidelines and FDA-aligned (US) clinical standards. Most established centres including FMRI also hold NABH and (where applicable) JCI accreditation.
The bottom line
- Nuclear medicine uses radioactive molecules (radiopharmaceuticals) for both imaging (PET-CT, SPECT-CT) and treatment of disease; in cancer care it images biological process (glucose metabolism, receptor expression) and delivers targeted radiation through the same biological targeting[1].
- The theranostic principle pairs a diagnostic imaging agent (e.g., Ga-68 PSMA, Ga-68 DOTATATE) with a matched therapy (Lu-177 PSMA-617, Lu-177 DOTATATE) sharing the same molecular target — the scan confirms eligibility, the therapy treats[3].
- Lu-177 PSMA-617 (Pluvicto, FDA 2022, EMA 2023) is approved for PSMA-positive mCRPC based on VISION (rPFS HR 0.40, OS HR 0.62)[13].
- Lu-177 DOTATATE (Lutathera, FDA 2018, EMA 2017, label expanded 2024) is approved for SSTR-positive GEP-NETs based on NETTER-1 and NETTER-2[4][14].
- Y-90 TARE delivers locoregional radioembolization for liver malignancies; LEGACY and DOSISPHERE-01 underpin its clinical use including as bridge-to-transplant in HCC[15].
- I-131 (decades-established for differentiated thyroid cancer) and Ra-223 (FDA/EMA 2013 for symptomatic bone-metastatic CRPC) are further established nuclear medicine therapies with mature evidence bases[16][17].
- Indian nuclear medicine practice operates under AERB Safety Code SC-2, DCGI / CDSCO regulation, and BRIT supply, with most established centres NABH-accredited and aligned with EANM and SNMMI procedure guidelines[21].
Important
This article is a patient-level pillar guide to nuclear medicine in cancer diagnosis and treatment. Individual treatment decisions require formal multidisciplinary review and depend on cancer type, stage, prior treatment, organ reserve, and patient values. The article is not a substitute for clinical consultation.
"Nuclear medicine is not a single technology — it is a discipline that uses radioactive molecules to see and to treat disease, often using the same molecular target twice. The diagnostic scan confirms the target is there; the matched therapy delivers radiation to it. The theranostic principle is what has transformed the field in the past decade."
Dr. Ishita B. Sen, MD · Director & Chief, Nuclear Medicine, FMRI
Nuclear medicine consultation · FMRI
At FMRI Gurugram, nuclear medicine consultation covers eligibility review for Lu-177 PSMA, Lu-177 DOTATATE PRRT, Y-90 TARE, I-131 thyroid ablation, and Ra-223 bone-metastatic CRPC therapy. Imaging eligibility includes Ga-68 PSMA PET, Ga-68 DOTATATE PET, FDG PET, and Tc-99m bone scan. All procedures follow AERB Safety Code SC-2 and EANM-aligned procedure guidelines.
Request consultation · WhatsApp +91 8800 988936
For patients & referring clinicians
Frequently asked questions
Q01
What is nuclear medicine?
Nuclear medicine is the medical speciality that uses small amounts of radioactive material (radiopharmaceuticals) to diagnose and treat disease. Unlike X-ray and CT, which pass radiation through the body from outside, nuclear medicine works from the inside: a radioactive molecule is given to the patient (intravenously, orally, or by injection), travels to its biological target, and either emits signals that imaging cameras detect or delivers radiation directly to disease tissue. In cancer it is used for imaging (PET-CT, SPECT-CT) and for therapy (Lu-177 PSMA, Lu-177 DOTATATE PRRT, Y-90 TARE, I-131, Ra-223) [1].
Q02
How does nuclear medicine work?
Nuclear medicine works by attaching a radioactive isotope to a targeting molecule. The targeting molecule (often a small peptide or antibody) binds a specific marker on tumour cells; the radioactive isotope either emits signals that imaging cameras detect (for diagnostic scans) or emits radiation that damages tumour cells (for therapy). The targeting and the radiation come together as a single molecule that locates disease tissue and acts on it preferentially over normal tissue. The same target principle can drive both imaging and therapy — the theranostic approach [1][3].
Q03
What does nuclear medicine do in cancer?
In cancer, nuclear medicine does two things: (1) it images the disease — FDG PET-CT for metabolic activity, Ga-68 PSMA PET for prostate cancer, Ga-68 DOTATATE PET for neuroendocrine tumours, Tc-99m bone scan for skeletal metastasis, etc.; and (2) it treats the disease — Lu-177 PSMA-617 for PSMA-positive mCRPC, Lu-177 DOTATATE for somatostatin-receptor-positive NETs, Y-90 microspheres for liver malignancies, I-131 for differentiated thyroid cancer, Ra-223 for symptomatic bone-metastatic CRPC. Each application uses a specific radiopharmaceutical and has specific eligibility, evidence base, and indications [2].
Q04
What is the difference between nuclear medicine and radiology?
Conventional radiology (X-ray, CT, MRI, ultrasound) images anatomy: shape, size, density, edges. The radiation in X-ray and CT comes from outside the body and passes through. Nuclear medicine images biological function — what is metabolically active, what binds a receptor, what concentrates a peptide — and the radiation comes from inside the body, from a radiopharmaceutical the patient receives. The same anatomical structure can look identical on CT and very different on PET because the question being asked is different. Modern hybrid scanners (PET-CT, SPECT-CT) combine the two for simultaneous functional and anatomical imaging [1].
Q05
What is theranostics?
Theranostics is the principle of using the same biological target for both diagnosis and therapy — a diagnostic imaging agent and a therapeutic agent share the same targeting molecule but carry different radionuclides. The classic example: Ga-68 DOTATATE PET-CT confirms somatostatin receptor 2 expression in neuroendocrine tumours; Lu-177 DOTATATE then delivers therapy to the same receptor. Or: Ga-68 PSMA PET-CT confirms PSMA expression; Lu-177 PSMA-617 delivers therapy. The advantage is patient selection — the imaging scan confirms the disease expresses the target before therapy is committed [3].
Q06
What is PET imaging and what is SPECT imaging?
PET (Positron Emission Tomography) detects pairs of 511 keV photons emitted when a positron from the radiopharmaceutical annihilates with an electron in tissue. Modern clinical PET-CT achieves spatial resolution of about 4-5 mm. Common cancer PET tracers: F-18 FDG, Ga-68 PSMA, F-18 PSMA, Ga-68 DOTATATE. SPECT (Single Photon Emission Computed Tomography) detects single gamma photons emitted directly by the radionuclide. Spatial resolution typically 10-15 mm. Common cancer SPECT tracers: Tc-99m MDP (bone scan), I-123/I-131 (thyroid), Lu-177 SPECT for post-therapy distribution imaging. Both modalities now combine with a low-dose CT (PET-CT, SPECT-CT) for simultaneous anatomical and functional imaging [6][7].
Q07
What is FDG PET-CT used for?
F-18 fluorodeoxyglucose (FDG) PET-CT is the most widely used PET imaging agent in oncology. FDG is a glucose analogue: cancer cells with increased glucose uptake (the Warburg effect) accumulate FDG preferentially relative to most normal tissues. FDG PET-CT is established for staging at diagnosis (lymphoma, oesophageal, head and neck, lung, melanoma, and others), response assessment after chemotherapy or radiation (Deauville score for lymphoma, PERCIST for solid tumours), restaging when markers rise, and detection of unknown primary in patients with metastatic disease of unknown origin. FDG is not cancer-specific — it accumulates in inflammation, infection, and active muscle — requiring expert interpretation [8].
Q08
What is Lu-177 used for?
Lutetium-177 (Lu-177) is the most widely used therapeutic radionuclide in modern radioligand therapy. Two Lu-177-based therapies are currently FDA / EMA approved: Lu-177 PSMA-617 (Pluvicto) for PSMA-positive mCRPC (FDA 2022, EMA 2023, label expanded 2025) based on the VISION and PSMAfore trials; and Lu-177 DOTATATE (Lutathera) for somatostatin-receptor-positive gastroenteropancreatic NETs (FDA 2018, EMA 2017, label expanded 2024) based on NETTER-1 and NETTER-2. Lu-177 is a beta-emitter with half-life 6.65 days, mean range in tissue ~0.7 mm, and low-yield gamma emission allowing post-therapy SPECT imaging [12][13][14].
Q09
What is Y-90 used for?
Yttrium-90 (Y-90) is used for transarterial radioembolization (TARE) of liver malignancies. Y-90-loaded microspheres are infused directly into the hepatic arterial supply where they lodge in the microvasculature and deliver short-range beta radiation. Approved indications include hepatocellular carcinoma (including as bridge to transplant), liver-dominant metastatic colorectal cancer, and neuroendocrine liver metastases. Evidence base includes LEGACY (88% ORR in solitary HCC ≤8 cm with radiation segmentectomy), DOSISPHERE-01 (personalised vs standard dosimetry, OS 26.6 vs 10.7 months), and PREMIERE (TARE longer time-to-progression than TACE in HCC). Y-90 is a pure beta-emitter, mean range in tissue ~2.5 mm, half-life 2.67 days [15].
Q10
What is I-131 used for?
Iodine-131 (I-131) is the oldest established radiotherapeutic in oncology, used since the 1940s. It is a beta-emitter with half-life 8 days. For differentiated thyroid cancer (papillary, follicular), I-131 is used after total thyroidectomy to ablate thyroid remnant and treat residual or metastatic disease. The sodium-iodide symporter (NIS) on thyroid cells provides the targeting mechanism — no separate targeting molecule is needed. I-131 is also used for hyperthyroidism (lower doses than for cancer). ATA, NCCN, and ESMO guidelines provide established indications and dosing [16].
Q11
How safe is nuclear medicine?
Nuclear medicine involves radiation exposure that is justified by the diagnostic information gained (for imaging) or therapeutic benefit (for therapy). A typical FDG PET-CT delivers approximately 5-10 mSv effective dose, similar to or slightly more than a diagnostic CT scan. Therapy exposure makes the patient the radiation source for days to weeks; discharge instructions cover distance from family, sleeping arrangements, and contact with pregnant women and young children. Specific side effects vary by therapy (see our cross-therapy side-effects article). Nuclear medicine practice operates under strict regulatory oversight — AERB in India, FDA in the US, EMA in Europe — and within EANM and SNMMI procedure guidelines [20][21].
Q12
How do I find out if nuclear medicine is right for my cancer?
At FMRI Gurugram, nuclear medicine consultation covers eligibility review for Lu-177 PSMA, Lu-177 DOTATATE PRRT, Y-90 TARE, I-131 thyroid ablation, and Ra-223 bone-metastatic CRPC therapy. Imaging eligibility covers Ga-68 PSMA PET, Ga-68 DOTATATE PET, FDG PET, and Tc-99m bone scan. The consultation includes multidisciplinary tumour board review and explicit discussion of available alternatives. All procedures follow AERB Safety Code SC-2 and EANM-aligned procedure guidelines. WhatsApp +91 8800 988936 to begin a confidential review.
Citations & references
All clinical numbers above are sourced from the primary literature listed below. Every reference links to the open journal page or the regulatory archive — open in a new tab to verify.
[1] National Institute of Biomedical Imaging and Bioengineering (NIBIB), NIH. Nuclear Medicine — what it is and how it is used.
View source ↗[2] Society of Nuclear Medicine and Molecular Imaging (SNMMI). What is Nuclear Medicine and Molecular Imaging?
View source ↗[3] Sgouros G, Bodei L, McDevitt MR, Nedrow JR. Radiopharmaceutical therapy in cancer: clinical advances and challenges.
Nat Rev Drug Discov. 2020;19(9):589-608.
View source ↗[4] Hennrich U, Kopka K. Lutathera®: The First FDA- and EMA-Approved Radiopharmaceutical for PRRT.
Pharmaceuticals (Basel). 2019;12(3):114.
View source ↗[5] Notni J, Wester HJ. A practical guide to selectivity, sensitivity and specificity of radiolabelled molecular probes.
Eur J Nucl Med Mol Imaging. 2018.
View source ↗[6] Townsend DW. Physical principles and technology of clinical PET imaging.
Ann Acad Med Singapore. 2004;33(2):133-145.
View source ↗[7] Wernick MN, Aarsvold JN. Emission Tomography: The Fundamentals of PET and SPECT.
Academic Press; 2004.
View source ↗[8] Boellaard R, Delgado-Bolton R, Oyen WJG, et al. FDG PET/CT: EANM procedure guidelines for tumour imaging: version 2.0.
Eur J Nucl Med Mol Imaging. 2015;42(2):328-354.
View source ↗[9] Vali R, Loidl W, Pirich C, et al. Imaging of prostate cancer with PET/CT using
18F-fluorocholine.
Am J Nucl Med Mol Imaging. 2015;5(2):96-108.
View source ↗[10] Bouvet V, Wuest M, Tam PH, et al. Targeting radionuclide imaging of cancer.
Curr Drug Targets. 2018.
View source ↗[11] Hofman MS, Lawrentschuk N, Francis RJ, et al. Prostate-specific membrane antigen PET-CT in patients with high-risk prostate cancer before curative-intent surgery or radiotherapy (proPSMA).
Lancet. 2020;395(10231):1208-1216.
View source ↗[12] Kratochwil C, Fendler WP, Eiber M, et al. EANM procedure guidelines for radionuclide therapy with
177Lu-labelled PSMA-ligands.
Eur J Nucl Med Mol Imaging. 2019;46(12):2536-2544.
View source ↗[13] Sartor O, de Bono J, Chi KN, et al. Lutetium-177-PSMA-617 for Metastatic Castration-Resistant Prostate Cancer (VISION).
N Engl J Med. 2021;385(12):1091-1103.
View source ↗[14] Singh S, Halperin D, Myrehaug S, et al. [
177Lu]Lu-DOTA-TATE plus long-acting octreotide versus high-dose long-acting octreotide for the treatment of newly diagnosed, advanced grade 2-3, well-differentiated, gastroenteropancreatic neuroendocrine tumours (NETTER-2).
Lancet. 2024;403(10446):2807-2817.
View source ↗[15] Salem R, Johnson GE, Kim E, et al. Yttrium-90 Radioembolization for the Treatment of Solitary, Unresectable HCC: The LEGACY Study.
Hepatology. 2021;74(5):2342-2352.
View source ↗[16] Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer.
Thyroid. 2016;26(1):1-133.
View source ↗[17] Parker C, Nilsson S, Heinrich D, et al. Alpha emitter radium-223 and survival in metastatic prostate cancer (ALSYMPCA).
N Engl J Med. 2013;369(3):213-223.
View source ↗[18] Strosberg J, El-Haddad G, Wolin E, et al. Phase 3 Trial of
177Lu-Dotatate for Midgut Neuroendocrine Tumors (NETTER-1).
N Engl J Med. 2017;376(2):125-135.
View source ↗[19] NCCN Clinical Practice Guidelines in Oncology. National Comprehensive Cancer Network.
View source ↗[20] International Commission on Radiological Protection (ICRP). Recommendations of the ICRP. ICRP Publication 103.
View source ↗[21] Atomic Energy Regulatory Board (Government of India). Safety Code for Nuclear Medicine Facilities. AERB/RF-MED/SC-2 (Rev. 2).
View source ↗[22] Bozkurt MF, Virgolini I, Balogova S, et al. Guideline for PET/CT imaging of neuroendocrine neoplasms with
68Ga-DOTA-conjugated somatostatin receptor targeting peptides.
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About the Author
Dr. Ishita B. Sen
MBBS · MD (Nuclear Medicine) · DNB · Post-doctoral Fellowship, Memorial Sloan Kettering Cancer Center, New York
Director and Chief of Nuclear Medicine at Fortis Memorial Research Institute. Co-founder of Theranostic Physicians Private Limited (TPPL). Two decades of clinical practice in PSMA imaging and PSMA-directed radioligand therapy, with one of the largest Indian institutional experiences in Lu-PSMA.