# Ata Rai Decision

> ATA RAI Remnant Ablation / Adjuvant Therapy Decision Tool

- Skill: `dromlakhani/ata-rai-decision` (Agent Skill)
- Install (CLI): `npx skillmds add dromlakhani/ata-rai-decision`
- Raw SKILL.md: https://api.skillmd.com/api/skills/dromlakhani/ata-rai-decision/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: dromlakhani (https://skillmd.com/u/dromlakhani)
- Updated: 2026-08-19
- Page: https://skillmd.com/skills/dromlakhani/ata-rai-decision

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# ATA RAI Remnant Ablation / Adjuvant Therapy Decision Tool
**Source:** 2015 ATA Management Guidelines — Recommendations 51–55 and Table 14.  
Haugen et al. Thyroid 2016;26(1). DOI: 10.1089/thy.2015.0020

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## PREREQUISITE

Before making a RAI decision:
1. Assign the **ATA Initial Risk Tier** (Low / Intermediate / High) → use the ATA DTC Risk Stratification skill
2. Confirm surgery: near-total or total thyroidectomy (RAI decision is only relevant after total/near-total thyroidectomy)
3. Confirm no contraindications: pregnancy, lactation, iodine overload (recent CT contrast)

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## STEP 1 — Understand the Three Indications for RAI

| RAI Goal | Definition | When Used |
|---|---|---|
| **Remnant ablation** | Destroy residual normal thyroid tissue to improve Tg monitoring sensitivity | Low–intermediate risk with no known residual disease |
| **Adjuvant therapy** | Treat likely but unproven microscopic residual disease | Intermediate risk with high-risk pathologic features |
| **Treatment** | Known residual or metastatic disease (structural/functional) | High risk, incomplete resection, distant mets |

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## STEP 2 — Apply the Risk-Stratified Decision Framework

### ❌ ATA LOW Risk — RAI NOT Routinely Recommended

**Applies to:**
- Unifocal PTC ≤1 cm (T1a) — intrathyroidal, no ETE, no LN involvement
- Intrathyroidal PTC T1b–T2 (1–4 cm), N0, no aggressive histology, no vascular invasion
- Intrathyroidal FTC with capsular invasion only or minimal vascular invasion (≤3 foci)
- Intrathyroidal multifocal PTMC (all foci <1 cm) without other risk factors

**Rationale:** RAI remnant ablation has not been shown to reduce recurrence or mortality in these patients. Surveillance with Tg and neck US is sufficient.

**Exception — consider RAI even in Low Risk if:**
- Aggressive histologic subtype (tall cell, hobnail, columnar)
- Vascular invasion present
- Patient/clinician preference for complete ablation to facilitate surveillance

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### 🔄 ATA LOW–INTERMEDIATE Risk (T3 N0 or pN1a) — CONSIDER RAI

**Applies to:**
- Microscopic ETE (pT3a) into perithyroidal soft tissue, N0
- pN1a (central neck nodes positive) — ≤5 nodes, all <3 cm
- T1–T2 with 1–4 positive central nodes <0.2 cm (low-volume)

**Decision:** Individualise based on:
- Number and size of positive nodes
- Presence of vascular invasion
- Aggressive histologic features
- Patient age and comorbidities
- Post-surgical Tg level

→ If nodes are ≤5 micrometastases all <0.2 cm → may not require RAI  
→ If >5 positive nodes or any node >0.2 cm but <3 cm → RAI generally favored

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### ✅ ATA INTERMEDIATE Risk (pN1a or pN1b, aggressive features) — RAI GENERALLY RECOMMENDED

**Applies to:**
- Microscopic ETE with RAI-avid neck uptake on first scan
- Aggressive histologic subtype
- PTC with vascular invasion
- pN1 (central or lateral) with >5 nodes, all <3 cm
- Multifocal PTMC with ETE + BRAF mutation

**Rationale:** Adjuvant RAI reduces recurrence risk in this group; evidence supports benefit even without distant metastases.

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### ✅✅ ATA HIGH Risk — RAI ROUTINELY RECOMMENDED

**Applies to:**
- Gross extrathyroidal extension (macroscopic pT4)
- Incomplete surgical resection (R1 or R2)
- Distant metastases (M1)
- Postoperative Tg suggesting distant disease
- pN1 with any single node ≥3 cm
- FTC with extensive vascular invasion (≥4 foci)

**Rationale:** RAI is a primary therapeutic agent. Dosing should be tailored to disease burden.

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## STEP 3 — RAI Administration Practicalities

### Preparation
- **Thyroid hormone withdrawal** (preferred for high-risk and treatment doses): stop levothyroxine 3–4 weeks before; switch to T3 for 2 weeks, then stop T3 2 weeks before RAI
- **Recombinant human TSH (rhTSH / Thyrogen):** Acceptable alternative for remnant ablation (2 IM injections on Days 1 and 2; RAI on Day 3) — avoids hypothyroid morbidity; equivalent efficacy for ablation in low–intermediate risk
- **Low-iodine diet:** 1–2 weeks before RAI (restrict iodine intake to <50 mcg/day)
- **Hold iodine-containing agents:** Recent IV contrast → delay RAI 6–8 weeks; amiodarone → prolonged delay

### Administered Activity

| Indication | Typical Activity |
|---|---|
| Remnant ablation (low risk, limited remnant) | 1.1 GBq (30 mCi) — equivalent to high-dose empirically |
| Remnant ablation (intermediate risk) | 3.7 GBq (100 mCi) |
| Known residual disease / high-risk adjuvant | 3.7–7.4 GBq (100–200 mCi) |
| Distant metastases (lung/bone) | 5.5–7.4 GBq (150–200 mCi); dosimetry in selected cases |

> Note: 30 mCi has been shown equivalent to 100 mCi for remnant ablation in ESTIMABL and HiLo trials — use lower dose for remnant ablation in low-risk patients to minimise adverse effects.

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## STEP 4 — Post-RAI Assessment

- **Post-treatment whole body scan (Rx-WBS):** Perform 5–8 days after RAI administration
  - Identifies previously unknown metastatic foci
  - Positive neck uptake in the thyroid bed is expected; uptake elsewhere changes staging and management
- **Serum Tg + anti-Tg antibodies:** Measure at time of RAI preparation (TSH-stimulated)
  - Document baseline for future comparisons
- **Follow-up:** 6–12 months → thyroid neck US + TSH-stimulated or suppressed Tg → reclassify using dynamic risk stratification

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## CLINICAL GUARDRAILS

- **Don't give RAI reflexively** — ATA Low-risk unifocal T1a PTC has no proven benefit from RAI; avoid unnecessary treatment
- **rhTSH vs. withdrawal is not equivalent for all patients** — rhTSH is acceptable for remnant ablation in low–intermediate risk; for known distant disease, withdrawal may be preferred (higher TSH levels may improve RAI uptake)
- **30 mCi is enough for remnant ablation** — do not dose-escalate to 100 mCi for pure remnant ablation in low–intermediate risk patients
- **Iodine load is a contraindication** — check for recent CT contrast before scheduling RAI; a 6–8 week delay is required after IV iodinated contrast
- **Anti-Tg antibodies interfere with Tg assays** — if anti-Tg is positive, Tg cannot be reliably interpreted; document and track anti-Tg trend instead
- **Whole body scan for staging, not routine screening** — do not perform diagnostic WBS routinely before RAI in low-risk patients; it adds radiation exposure without management benefit
- **Breastfeeding must be stopped ≥6 weeks before RAI** — and is contraindicated for 4–8 weeks after RAI
- **Pregnancy is an absolute contraindication** — confirm β-hCG negative before RAI in women of childbearing potential