TARGETED RADIOLIGAND THERAPY:
SEE IT. TREAT IT. GLOBALLY.

Radioligand therapy attaches radioactive atoms to molecular targeting ligands that seek out cancer-specific surface receptors — delivering lethal radiation directly to every cancer cell expressing the target, wherever it is in the body, while sparing normal tissue.

“Theranostics converts the diagnostic scan into the treatment plan: what you see on the PET scan is exactly where the therapeutic radioligand will go.”

• The Radioligand: Radio + Ligand

  Two components in one molecule: a targeting ligand (peptide, small molecule, or antibody) that binds with high affinity to a cancer-specific receptor, and a radionuclide that emits radiation locally at the cancer cell. Radiation range: 1–2mm for beta emitters (Lu-177); <100µm for alpha emitters (Ac-225).

• Theranostics: See It, Treat It

  Same targeting molecule attached to a diagnostic isotope (Ga-68) for PET imaging, then to a therapeutic isotope (Lu-177) for treatment. The pre-treatment PET scan confirms target expression, maps all disease sites, and predicts where the therapeutic agent will go — creating a patient-specific biodistribution map.

• vs External Beam Radiation

  External beam radiation travels through normal tissue to reach the tumour. Radioligand therapy circulates in the bloodstream, binds selectively to cancer cells at every site simultaneously — bone mets, lymph nodes, liver, lung — and delivers radiation locally without a beam path through normal tissue.

• Dosimetry: Personalised Dose Optimisation

  Advanced theranostics centres use serial post-therapy imaging to calculate actual radiation dose per tumour and organ-at-risk for each patient — enabling activity adjustment to maximise tumour dose while respecting organ tolerance. More individualised than fixed-activity protocols.

The choice of radionuclide determines therapeutic potency, radiation range in tissue, half-life, and safety profile. Beta emitters (Lu-177) are the current standard; alpha emitters (Ac-225) offer higher potency for resistant disease.

Two Phase III trials have established radioligand therapy as standard of care — one for neuroendocrine tumours, one for prostate cancer — with practice-changing survival data.

• Lu-177 DOTATATE (Lutathera) — NETs

  NETTER-1 Phase III trial: PFS 28.4 months vs 8.5 months with high-dose octreotide (HR 0.21 — 79% reduction in progression risk). FDA approved 2018, EMA 2017. Standard second-line treatment for progressive, SSTR-positive, well-differentiated gastroenteropancreatic NETs. Four cycles of 7.4 GBq each, 8 weeks apart.

• Lu-177 PSMA-617 (Pluvicto) — Prostate Cancer

  VISION Phase III trial (831 patients): OS 15.3 vs 11.3 months (38% reduction in death risk); rPFS 8.7 vs 3.4 months. FDA approved March 2022, EMA December 2022. Indicated for PSMA-positive mCRPC post-ARPI and taxane. PSMAfore trial supports earlier pre-taxane use — regulatory expansion ongoing.

• Ac-225 PSMA-617 — Alpha Therapy (Investigational)

  Same targeting molecule as Pluvicto but with alpha-emitting Ac-225 replacing Lu-177. Higher linear energy transfer causes more complex, less repairable DNA damage — meaningful responses in patients who progressed after Lu-177 PSMA. Phase III trials underway. Access currently via compassionate use at specialist centres. Limited by global Ac-225 production capacity.

• Ra-223 Dichloride (Xofigo) — Bone Mets

  Not a radioligand in the classical sense — a calcium mimetic that selectively incorporates into osteoblastic bone metastases. Alpha emitter; <100µm range. ALSYMPCA Phase III: OS benefit in mCRPC with bone mets. FDA/EMA approved. Only approved alpha-particle therapy globally; important component of bone metastasis toolkit in advanced prostate cancer.

Two Phase III randomised controlled trials have established radioligand therapy as the highest standard of evidence in its respective cancer types.

The success of Lutathera and Pluvicto has catalysed one of the most active oncology pipelines globally. FAPI, HER2, and alpha-particle programmes are the most advanced — with the potential to address cancers not accessible to current approved agents.

Radioligand therapy only benefits patients whose tumours express the relevant target. PET imaging confirmation of target expression is a mandatory prerequisite — not optional — before treatment.

1. 1

   Confirm Target Expression by PET Imaging

   Ga-68 DOTATATE PET/CT for NETs (Krenning score ≥3 required). Ga-68 PSMA-11 or F-18 DCFPyL PET/CT for prostate cancer (VISION criteria: ≥1 PSMA-positive lesion; no PSMA-negative lesions visible on conventional imaging).

2. 2

   Assess Bone Marrow Reserve

   CBC with differential: minimum thresholds for neutrophil count, haemoglobin, and platelets required before each cycle. Grade 3–4 haematological toxicity affects ~10–15% of patients; pre-treatment counts determine tolerability.

3. 3

   Assess Renal Function

   eGFR and kidney dimensions assessed before PRRT. Cumulative renal dose from multiple PRRT cycles requires careful baseline evaluation. Single functioning kidney or pre-existing renal impairment requires individualised risk-benefit assessment.

4. 4

   Confirm Prior Treatment History (Prostate Cancer)

   VISION trial approval requires prior ARPI (enzalutamide/abiraterone) and taxane chemotherapy. PSMAfore trial data may support pre-taxane access — regulatory expansion ongoing. Clinical trial enrolment can provide earlier access.

5. 5

   Multidisciplinary Review and Treatment Planning

   Nuclear medicine oncologist, treating oncologist, and radiation physicist review imaging, organ function, and prior therapy history to confirm eligibility, plan treatment activity, and establish renal protection protocol.

Radioligand therapy requires a specialist nuclear medicine facility with radionuclide handling infrastructure, radiation safety licensing, and trained nuclear medicine staff. Treatment is outpatient or short inpatient in most cases.

• Treatment Day: Amino Acid Infusion (PRRT Only)

  For DOTATATE therapy: renal protective lysine-arginine amino acid infusion started 30 minutes before and continued 3–4 hours after radionuclide administration. Significantly reduces tubular reabsorption and renal radiation dose. Anti-emetic premedication is standard.

• Radioligand Administration

  Intravenous infusion over 20–30 minutes via lead-shielded administration system. Patient monitored for allergic or infusion reactions. Most patients experience minimal acute symptoms — mild nausea or fatigue. Severe acute reactions are uncommon.

• Post-Therapy SPECT/CT Imaging (24–48 Hours)

  Lu-177 emits gamma rays alongside therapeutic beta particles, enabling SPECT/CT imaging 24–48 hours post-infusion. Confirms tumour uptake, identifies unexpected biodistribution, and provides organ dosimetry data. Standard practice at all accredited centres.

• Radiation Precautions at Home (Lu-177: 2–7 Days)

  Avoid prolonged close contact with children or pregnant women for 2–7 days. Flush toilet twice, wash hands frequently, launder clothes separately, sleep separately from partner if preferred. Written centre-specific instructions provided. Most patients return home same day or next day.

• Treatment Schedule

  Lu-177 DOTATATE: 4 cycles × 7.4 GBq, 8 weeks apart (total course ~24–32 weeks). Lu-177 PSMA (VISION protocol): up to 6 cycles every 6 weeks. Response assessed by tumour markers and repeat PET imaging after the treatment course.

Radioligand therapy with Lu-177 agents has a generally manageable safety profile compared with cytotoxic chemotherapy. Primary risks are haematological and renal — both monitored before each cycle.

Access is geographically unequal — concentrated at specialist nuclear medicine centres in high-income countries. India currently offers the most cost-effective commercially available PRRT for international patients from South Asia and the Middle East.

Cost per cycle varies 10–20 fold between countries. India provides the most cost-accessible commercially available PRRT globally, with equivalent nuclear medicine expertise at accredited centres.

Radioligand therapy is increasingly studied in combination with PARP inhibitors and checkpoint inhibitors — exploiting DNA repair and immune synergy to improve response rates and expand eligible populations.

• RLT + PARP Inhibitors

  Radiation-induced DNA damage activates PARP-mediated repair. PARP inhibitors block this, amplifying RLT lethality — particularly in BRCA-mutated or HRR-deficient tumours. UpFrontPSMA trial evaluates Lu-177 PSMA + olaparib in mCRPC. Synthetic lethality mechanism most relevant in HRD-positive disease.

• RLT + Checkpoint Inhibitors

  Radioligand therapy induces immunogenic cell death — releasing tumour antigens that may sensitise tumours to PD-1/PD-L1 inhibition. Trials evaluating Lu-177 DOTATATE + PD-1 inhibitors in NETs, and Lu-177 PSMA + pembrolizumab in prostate cancer, test whether RLT creates an immunologically responsive tumour microenvironment.

• RLT Sequencing with Hormonal Therapy

  TheraP trial (Lu-177 PSMA vs cabazitaxel): 66% vs 37% PSA50 response — supporting RLT as a chemotherapy alternative. Optimal sequencing of PSMA therapy with ARPI and taxane chemotherapy in prostate cancer is an active investigation. Earlier-line use (PSMAfore) may shift the paradigm.

• Alpha Escalation: Lu-177 → Ac-225

  For patients progressing after Lu-177 PSMA, Ac-225 PSMA offers a higher-potency alpha particle approach. Alpha radiation's oxygen-independent cell killing may also overcome the radioresistance of hypoxic tumour cells. Phase III trials underway; limited by global Ac-225 production capacity.

Frequently Asked Questions