Skip to content

Lung adenocarcinoma — Staging

TL;DR — TNM describes anatomic extent, not tumor biology: T captures primary-tumor size and invasion, N regional nodes, and M distant spread. The ninth edition took effect in 2025, retaining most T definitions while revising N and M subdivisions and stage groups using an international database of 124,581 registrations, 76,518 of which informed stage-group analysis (Detterbeck 2024, PMID 38885896; Rami-Porta 2024, PMID 38447919). Stage determines curative local versus systemic treatment intent, but genotype, histologic grade, performance status, and ctDNA add prognosis within every stage. “Oligometastatic” NSCLC is a treatment state rather than a formal replacement for M staging: small randomized phase II trials support local consolidation in selected non-progressing patients, while optimal lesion count, timing, and driver-specific selection remain unresolved (Gomez 2019, PMID 31067138; Iyengar 2018, PMID 28973074).

What staging does—and does not do

TNM provides a common language for prognosis, trial stratification, surgery, radiotherapy, and systemic therapy. It is periodically recalibrated against survival data rather than derived from a biological model (Detterbeck 2016, PMID 27448762). External validation of the eighth edition in the NCDB and independent surgical cohorts confirmed ordered survival separation but also exposed overlap between adjacent groups (Chansky 2017, PMID 28461257; Sui 2017, PMID 28782726).

Layer Question answered Not answered
Clinical TNM (cTNM) What is the apparent extent before definitive treatment? Microscopic nodal disease or final invasive size
Pathologic TNM (pTNM) What did complete resection and nodal evaluation show? Biology of unresected metastatic deposits
Post-neoadjuvant ypTNM What viable disease remains after induction therapy? Pretreatment burden by itself
Molecular/pathologic modifiers Grade, STAS, driver, PD-L1, ctDNA They do not change TNM category unless incorporated formally

T: primary tumor

T category is driven by invasive size, airway/pleural/chest-wall/mediastinal invasion, atelectasis or pneumonitis, and separate tumor nodules. For part-solid adenocarcinoma, pathologic invasive size—not total lepidic span—anchors pT, while clinical solid-component measurement approximates invasion.

T concept Ninth-edition framing Adenocarcinoma-specific pitfall
Tis AIS Requires complete pathologic assessment; biopsy cannot prove AIS
T1mi MIA with ≤5 mm invasion Total lesion may be ≤3 cm while invasive size is much smaller
T1 ≤3 cm, size subcategories retained Measure invasive component in lepidic tumors
T2 >3–5 cm or qualifying local feature Visceral pleural invasion can up-category a small tumor
T3 >5–7 cm, specified local invasion, or same-lobe nodule Distinguish intrapulmonary metastasis from synchronous primary
T4 >7 cm, major mediastinal invasion, or ipsilateral different-lobe nodule Multifocal mucinous disease may spread aerogenously

The ninth-edition overview reports that T descriptors remained comparatively stable while changes concentrated in N, M, and stage grouping (Detterbeck 2024, PMID 38885896; Klug 2024, PMID 39541244). STAS was evaluated in 4,061 pathologic stage-I NSCLCs and recommended as a histologic descriptor, not a determinant of T category, because prognostic association did not justify stage migration (Travis 2024, PMID 38508515).

N: regional lymph nodes

Nodal stage depends on anatomic station and, in the ninth edition, the extent across stations within N2 disease. Accurate staging requires a map-based approach and adequate invasive sampling when results change curative strategy.

N category Anatomic concept Ninth-edition nuance
N0 No regional nodal metastasis Imaging-negative nodes can still harbour micrometastasis
N1 Ipsilateral peribronchial/hilar/intrapulmonary nodes Single vs multiple stations affects prognosis but core category persists
N2a Single ipsilateral mediastinal/subcarinal station Better prognosis than multistation N2
N2b Multiple ipsilateral mediastinal/subcarinal stations Newly emphasized subdivision
N3 Contralateral mediastinal/hilar or supraclavicular/scalene nodes Usually precludes upfront surgery

PET/CT is a probability tool, not histology: inflammatory nodes can be avid and small metastatic nodes non-avid. EBUS/EUS needle staging and mediastinoscopy are selected according to tumor location, imaging, and the consequence of error. Stage labels should state whether nodes were radiographic, cytologic, or surgically confirmed.

M: distant disease

M category Concept Ninth-edition rationale
M1a Contralateral lung nodule, pleural/pericardial nodules or malignant effusion Intrathoracic metastatic compartment retained
M1b Single extrathoracic metastasis Separates potentially locally consolidatable burden
M1c1 Multiple extrathoracic metastases in one organ system New separation from multi-organ disease
M1c2 Multiple extrathoracic metastases across organ systems Worst anatomic metastatic extent

The ninth-edition M analysis included 14,937 stage IVA–IVB NSCLCs and supported splitting multiple extrathoracic metastases by single versus multiple organ systems (Fong 2024, PMID 38320664). Population studies show that bone, brain, liver, and adrenal patterns differ in frequency and prognosis, but registry ascertainment and treatment selection prevent these from replacing TNM (Riihimäki 2014, PMID 25130083; Wang 2023, PMID 36896839).

Adenocarcinoma is enriched among NSCLC with brain metastases, especially in EGFR- and ALK-driven disease. Baseline brain MRI is therefore important in stage II–IV evaluation and when neurologic symptoms occur, even if extracranial burden seems limited.

Ninth-edition stage groups

The ninth-edition stage-group proposal used 58,193 clinical-stage, 39,192 pathologic-stage, and 62,611 best-stage cases after exclusions. Changes were chosen to improve prognostic separation and clinical coherence, not to make every adjacent survival curve non-overlapping (Rami-Porta 2024, PMID 38447919).

Broad stage Anatomic frame Typical intent
0 AIS Local cure
I Localized, node-negative Surgery or definitive radiotherapy; biomarker-defined adjuvant options in selected cases
II Larger/local invasion and/or limited ipsilateral nodes Multimodality curative intent
III Locoregionally advanced, mediastinal nodes and/or major invasion Heterogeneous; surgery in selected configurations, otherwise definitive chemoradiation/systemic integration
IVA M1a or M1b Systemic therapy; selected local consolidation
IVB Multiple extrathoracic metastases Systemic treatment is the anchor

Institutional validation of the eighth edition showed meaningful but imperfect discrimination, reminding users that stage migration can result from better imaging rather than biological improvement (Hwang 2019, PMID 31863848). Comparisons across eras must specify TNM edition and whether old cases were reclassified.

Staging work-up

Modality Main staging role Limitation
Contrast CT chest/upper abdomen Primary tumor, nodes, liver/adrenal overview Size criteria miss microscopic nodes
FDG PET/CT Extracranial nodal and metastatic survey Inflammation false positives; low-avid lepidic/mucinous tumors
Brain MRI Detect CNS metastases Incidental lesions; access variation
EBUS/EUS Minimally invasive mediastinal/hilar confirmation Operator and station access dependence
Mediastinoscopy/surgical sampling Higher-volume tissue and nodal confirmation Invasive; selective use after needle staging
Biopsy of distant lesion Confirms M disease and obtains molecular tissue Choose safest site without exhausting diagnostic material

Biopsy strategy should answer the highest-impact uncertainty. Confirming a suspected solitary metastasis can change a case from curative stage III to stage IV; confirming mediastinal nodes can prevent futile thoracotomy. When tissue is scarce, pathology, staging, and molecular teams should coordinate the sampling plan.

Multiple lung lesions

Separate nodules may represent synchronous primaries, intrapulmonary metastases, multifocal ground-glass/lepidic tumors, or pneumonic-type mucinous spread. Classification integrates imaging, histology, nodal pattern, temporal behaviour, and—when available—comparative genomics. One simplistic rule (same mutation means metastasis; different mutation means separate primary) fails because common drivers can recur independently and tumors are heterogeneous.

Oligometastatic disease

Oligometastatic NSCLC denotes limited metastatic burden potentially amenable to ablation of all visible sites. It is biologically and temporally heterogeneous: synchronous versus metachronous, induced after systemic response, driver-positive versus driver-negative, and nodal versus organ disease.

Trial Selection Intervention Result
Gomez phase II ≤3 metastases, no progression after first-line systemic therapy Local consolidative therapy (LCT) to all sites vs maintenance/observation Long-term follow-up: median PFS 14.2 vs 4.4 mo; median OS 41.2 vs 17.0 mo (Gomez 2019, PMID 31067138)
Iyengar phase II Limited metastatic NSCLC after induction chemotherapy SABR to gross disease plus maintenance vs maintenance alone Median PFS 9.7 vs 3.5 mo; trial stopped early for efficacy (Iyengar 2018, PMID 28973074)
SABR-COMET Mixed primary cancers with 1–5 metastases Standard care ± SABR Longer-term OS benefit, but NSCLC subset small and mixed (Palma 2020, PMID 32484754)

These trials establish a selection-dependent signal, not a universal mandate to ablate every low-count metastasis. Small samples, early stopping, older systemic regimens, and survivor selection after induction limit transfer to current targeted and immune therapy. Modern trials must test whether local therapy adds benefit beyond highly effective CNS-active TKIs and chemo-immunotherapy.

Response and restaging

TNM stage is assigned at diagnosis and is not erased by response. After neoadjuvant therapy, ypTNM records residual viable disease; pathologic complete response and major pathologic response add prognostic information but do not rewrite pretreatment cTNM. In metastatic disease, RECIST response, CNS response, metabolic response, and ctDNA response describe different dimensions.

Open questions

  • Do ninth-edition N2a/N2b and M1c1/M1c2 subdivisions improve treatment selection, or only prognosis (Rami-Porta 2024, PMID 38447919; Fong 2024, PMID 38320664)?
  • Which patients with oncogene-driven oligometastatic disease benefit from local consolidation beyond a CNS-active TKI (Gomez 2019, PMID 31067138)?
  • Can ctDNA identify occult systemic disease among radiographically stage I–III adenocarcinomas and safely intensify or de-intensify therapy?
  • How should multifocal ground-glass adenocarcinomas be staged when lesions are clonally unrelated but numerous?
  • Should STAS remain a descriptor or enter future T/grading systems after prospective validation (Travis 2024, PMID 38508515)?

References

  1. Detterbeck FC, et al. The Proposed Ninth Edition TNM Classification of Lung Cancer. Chest. 2024. PMID 38885896
  2. Rami-Porta R, et al. The International Association for the Study of Lung Cancer Lung Cancer Staging Project: Proposals for Revision of the TNM Stage Groups in the Forthcoming (Ninth) Edition of the TNM Classification for Lung Cancer. J Thorac Oncol. 2024. PMID 38447919
  3. Klug M, et al. Proposed Ninth Edition TNM Staging System for Lung Cancer: Guide for Radiologists. Radiographics. 2024. PMID 39541244
  4. Travis WD, et al. The International Association for the Study of Lung Cancer (IASLC) Staging Project for Lung Cancer: Recommendation to Introduce Spread Through Air Spaces as a Histologic Descriptor in the Ninth Edition of the TNM Classification of Lung Cancer. Analysis of 4061 Pathologic Stage I NSCLC. J Thorac Oncol. 2024. PMID 38508515
  5. Asamura H, et al. IASLC Lung Cancer Staging Project: The New Database to Inform Revisions in the Ninth Edition of the TNM Classification of Lung Cancer. J Thorac Oncol. 2023. PMID 36773775
  6. Fong KM, et al. The International Association for the Study of Lung Cancer Staging Project for Lung Cancer: Proposals for the Revision of the M Descriptors in the Forthcoming Ninth Edition of the TNM Classification for Lung Cancer. J Thorac Oncol. 2024. PMID 38320664
  7. Hwang JK, et al. Validation of the Eighth Edition TNM Lung Cancer Staging System. J Thorac Oncol. 2020. PMID 31863848
  8. Sui X, et al. Validation of the Stage Groupings in the Eighth Edition of the TNM Classification for Lung Cancer. J Thorac Oncol. 2017. PMID 28782726
  9. Chansky K, et al. The IASLC Lung Cancer Staging Project: External Validation of the Revision of the TNM Stage Groupings in the Eighth Edition of the TNM Classification of Lung Cancer. J Thorac Oncol. 2017. PMID 28461257
  10. Detterbeck FC, et al. The IASLC Lung Cancer Staging Project: Methodology and Validation Used in the Development of Proposals for Revision of the Stage Classification of NSCLC in the Forthcoming (Eighth) Edition of the TNM Classification of Lung Cancer. J Thorac Oncol. 2016. PMID 27448762
  11. Riihimäki M, et al. Metastatic sites and survival in lung cancer. Lung Cancer. 2014. PMID 25130083
  12. Wang H, et al. Occurrence and prognosis of lung cancer metastasis to major organs: a population-based study. Eur J Cancer Prev. 2023. PMID 36896839
  13. Gomez DR, et al. Local Consolidative Therapy Vs. Maintenance Therapy or Observation for Patients With Oligometastatic Non-Small-Cell Lung Cancer: Long-Term Results of a Multi-Institutional, Phase II, Randomized Study. J Clin Oncol. 2019. PMID 31067138
  14. Gomez DR, et al. Local consolidative therapy versus maintenance therapy or observation for patients with oligometastatic non-small-cell lung cancer without progression after first-line systemic therapy: a multicentre, randomised, controlled, phase 2 study. Lancet Oncol. 2016. PMID 27789196
  15. Iyengar P, et al. Consolidative Radiotherapy for Limited Metastatic Non-Small-Cell Lung Cancer: A Phase 2 Randomized Clinical Trial. JAMA Oncol. 2018. PMID 28973074
  16. Palma DA, et al. Stereotactic Ablative Radiotherapy for the Comprehensive Treatment of Oligometastatic Cancers: Long-Term Results of the SABR-COMET Phase II Randomized Trial. J Clin Oncol. 2020. PMID 32484754
  17. Palma DA, et al. Stereotactic ablative radiotherapy versus standard of care palliative treatment in patients with oligometastatic cancers (SABR-COMET): a randomised, phase 2, open-label trial. Lancet. 2019. PMID 30982687
  18. Frankell AM, et al. The evolution of lung cancer and impact of subclonal selection in TRACERx. Nature. 2023. PMID 37046096
  19. Yotsukura M, et al. Long-Term Prognosis of Patients With Resected Adenocarcinoma In Situ and Minimally Invasive Adenocarcinoma of the Lung. J Thorac Oncol. 2021. PMID 33915249
  20. Chen D, et al. Tumor Spread Through Air Spaces in Non-Small Cell Lung Cancer: A Systematic Review and Meta-Analysis. Ann Thorac Surg. 2019. PMID 30914285
  21. Behera M, et al. Lung Adenocarcinoma Staging Using the 2011 IASLC/ATS/ERS Classification: A Pooled Analysis of Adenocarcinoma In Situ and Minimally Invasive Adenocarcinoma. Clin Lung Cancer. 2016. PMID 27137345
  22. de Koning HJ, et al. Reduced Lung-Cancer Mortality with Volume CT Screening in a Randomized Trial. N Engl J Med. 2020. PMID 31995683
  23. Forde PM, et al. Neoadjuvant Nivolumab plus Chemotherapy in Resectable Lung Cancer. N Engl J Med. 2022. PMID 35403841
  24. Wu YL, et al. Osimertinib in Resected EGFR-Mutated Non-Small-Cell Lung Cancer. N Engl J Med. 2020. PMID 32955177
  25. Cancer Genome Atlas Research Network, et al. Comprehensive molecular profiling of lung adenocarcinoma. Nature. 2014. PMID 25079552