# Sublobar Resection for Early-Stage Lung Cancer

## Overview

Sublobar resection includes anatomic segmentectomy and non-anatomic wedge resection. Historically considered a compromise operation for patients unable to tolerate lobectomy, two landmark trials — JCOG0802 and CALGB 140503 — have established segmentectomy as an equivalent alternative to lobectomy for select small peripheral NSCLC. This represents a paradigm shift in thoracic surgical oncology.

## Types of Sublobar Resection

### Anatomic Segmentectomy

Anatomic segmentectomy involves division of the segmental artery, vein, and bronchus with removal of the anatomic bronchopulmonary segment. It preserves more lung parenchyma than lobectomy while maintaining oncologic margins. The intersegmental plane must be identified, using the inflation-deflation technique, ICG fluorescence, or a stapler line. Commonly resected segments include the superior segment of the LLL (S6), the lingula, and the apical segment of the RUL.

### Wedge Resection

Wedge resection is a non-anatomic parenchymal resection using staplers. It is faster and technically simpler than segmentectomy but does not follow anatomic planes, limiting lymph node evaluation within the specimen. Local recurrence rates have historically been higher compared to lobectomy. Wedge resection is acceptable for pure ground glass lesions (AIS, MIA) and in patients with limited physiologic reserve.

## Landmark Trials

### JCOG0802 (Japan)

This prospective randomized trial compared segmentectomy versus lobectomy for peripheral NSCLC of 2 cm or smaller with a tumor consolidation ratio greater than 0.5 on CT. Segmentectomy showed non-inferior overall survival, with 5-year OS of 94.3% for segmentectomy versus 91.1% for lobectomy. The segmentectomy group had significantly better preserved pulmonary function. Local recurrence was higher in the segmentectomy group (10.5% versus 5.4%) but there was no OS difference. The conclusion is that segmentectomy is a standard option for peripheral NSCLC of 2 cm or smaller.

### CALGB 140503 (North America)

This prospective randomized trial compared sublobar resection (segmentectomy or wedge) versus lobectomy for peripheral NSCLC of 2 cm or smaller with confirmed N0 status. Disease-free survival was non-inferior for sublobar resection, with 5-year DFS of 63.6% for sublobar resection versus 64.1% for lobectomy, and no difference in overall survival. This trial notably included both wedge resection and segmentectomy, concluding that sublobar resection (including wedge) is non-inferior for small peripheral NSCLC.

<image>Summary comparison of JCOG0802 and CALGB 140503 trial designs, inclusion criteria, and key survival outcomes</image>

## Patient Selection Criteria

**Tumor size** should be 2 cm or smaller (per both trials). **Location** should be peripheral (outer third of the lung parenchyma). **Histology** should be confirmed or suspected NSCLC (excluding small cell and carcinoid). **Nodal status** should be clinically N0 (negative PET-CT and ideally intraoperative node assessment). **CT morphology** guides the approach: solid-predominant tumors favor segmentectomy over wedge, while ground glass-predominant (GGO) tumors have an excellent prognosis regardless of resection type and may be adequately treated with wedge. The consolidation-to-tumor ratio (CTR) is informative — tumors with CTR of 0.5 or less have extremely low recurrence. **Margin adequacy** is critical: the resection margin must be at least equal to the tumor diameter or at least 2 cm (whichever is smaller), as margins less than 1 cm are associated with higher recurrence.

## Segmentectomy Technique

### Preoperative Planning

High-resolution CT with 3D reconstruction defines segmental anatomy. The course and variations of the segmental artery, vein, and bronchus are identified. Software-based planning (such as OsiriX or Synapse Vincent) is increasingly used for complex segments.

### Intraoperative Steps

The segmental artery is identified and divided (there may be multiple branches). The segmental bronchus is identified and divided. The segmental vein is identified and divided (some surgeons preserve intersegmental veins). The intersegmental plane is then defined using one of several methods: the **inflation-deflation method** (ventilate the lung, clamp the segmental bronchus, deflate — the target segment remains inflated), **ICG fluorescence** (inject ICG intravenously after clamping the segmental artery — the ischemic segment does not fluoresce), or **jet ventilation** through the segmental bronchus. The intersegmental plane is divided using a stapler or electrocautery. An adequate margin (greater than the tumor diameter or greater than 2 cm) is confirmed.

### Lymph Node Assessment

Segmental and hilar (N1) nodes must be removed with the specimen. Systematic mediastinal (N2) lymph node sampling or dissection is still required. Intraoperative frozen section of N1/N2 nodes is recommended — if positive, conversion to lobectomy should be considered.

<image>Segmentectomy operative technique showing identification of intersegmental plane using the inflation-deflation method with the target segment remaining inflated</image>

## Wedge Resection: When Is It Enough?

### Appropriate Indications for Wedge

Wedge resection is appropriate for pure or predominant ground glass opacities (AIS, MIA, lepidic-predominant adenocarcinoma), lesions of 1 cm or smaller with adequate margins, patients with severely limited pulmonary reserve where segmentectomy is too much, multiple primary lung cancers requiring parenchymal preservation, and diagnostic resection with a plan for completion lobectomy if invasive cancer is confirmed.

### Margin Requirements

The minimum margin should be at least equal to tumor size or at least 2 cm. Intraoperative frozen section of the deepest margin should be obtained. If margins are inadequate, re-excision or conversion to segmentectomy or lobectomy is necessary.

## Comparison: Segmentectomy vs. Wedge vs. Lobectomy

| Parameter | Wedge | Segmentectomy | Lobectomy |
|-----------|-------|---------------|-----------|
| Anatomic dissection | No | Yes | Yes |
| LN in specimen | Minimal | Segmental N1 | Lobar N1 |
| Margin adequacy | Variable | Defined by plane | N/A (entire lobe) |
| Local recurrence | Higher | Slightly higher | Lowest |
| Pulmonary preservation | Most | Moderate | Least |
| Operative complexity | Lowest | Moderate-High | Moderate |

<image>Three-dimensional CT reconstruction showing segmental bronchopulmonary anatomy with planned segmentectomy resection boundary highlighted</image>

## Ground Glass Opacities and Subsolid Nodules

Pure GGO and part-solid nodules represent the adenocarcinoma spectrum. **AIS** (adenocarcinoma in situ) carries 100% 5-year survival after resection. **MIA** (minimally invasive adenocarcinoma) carries near 100% 5-year survival. **Lepidic-predominant invasive adenocarcinoma** has an excellent prognosis. For pure GGO of 2 cm or smaller, wedge resection with adequate margins is sufficient. A CTR of 0.25 or less may warrant surveillance alone; if resected, a limited resection is adequate. Multiple GGOs are common, and each should be managed independently based on size and growth.

## Clinical Pearls

The era of "lobectomy for all" is over for small peripheral NSCLC of 2 cm or smaller — segmentectomy is now a standard alternative. Margin adequacy is the single most important technical factor in sublobar resection, with a margin of at least the tumor size or at least 2 cm required. Mediastinal lymph node dissection must always be performed even with sublobar resection because accurate staging is not optional. For solid tumors, segmentectomy is preferred over wedge due to better oncologic margins and lymph node assessment. Ground glass-predominant tumors have an extremely favorable biology and should not be over-treated with lobectomy when a limited resection achieves cure. 3D CT reconstruction and ICG fluorescence have made complex segmentectomies safer and more precise. Intraoperative frozen section of lymph nodes should guide the extent of resection — positive N1 nodes should prompt consideration of lobectomy.

## References

- Saji H et al. "Segmentectomy versus lobectomy in small-sized peripheral non-small-cell lung cancer (JCOG0802/WJOG4607L)." *Lancet*. 2022.
- Altorki N et al. "Lobar or sublobar resection for peripheral stage IA non-small-cell lung cancer (CALGB 140503)." *N Engl J Med*. 2023.
- Ginsberg RJ, Rubinstein LV. "Randomized trial of lobectomy versus limited resection for T1 N0 non-small cell lung cancer (LCSG)." *Ann Thorac Surg*. 1995.
- Suzuki K et al. "Prognostic significance of the size of central fibrosis in peripheral adenocarcinoma of the lung." *Ann Thorac Surg*. 2000.
- NCCN Clinical Practice Guidelines: Non-Small Cell Lung Cancer. Version 2024.