From the Guidelines
Pulmonary adenocarcinoma in situ (AIS) is a distinct entity from invasive pulmonary adenocarcinoma, with a significantly better prognosis and different management approach, as emphasized by the revised classification of adenocarcinoma 1.
Key Differences
- Pulmonary adenocarcinoma in situ (AIS) is a pre-invasive lesion limited to the alveolar lining cells without invasion through the basement membrane, typically appearing as a ground-glass opacity on imaging and measuring less than 3 cm in diameter.
- Invasive pulmonary adenocarcinoma has breached the basement membrane and invaded surrounding lung tissue, often presenting with a solid component on imaging and carrying a more variable prognosis depending on stage.
Management Approach
- Treatment for AIS typically involves surgical resection alone, such as lobectomy or limited resection (segmentectomy or wedge resection) 1.
- Invasive adenocarcinoma may require more extensive surgery plus adjuvant chemotherapy, radiation, targeted therapy, or immunotherapy depending on stage and molecular characteristics.
Importance of Distinction
- The distinction between AIS and invasive adenocarcinoma is critical for proper staging, treatment planning, and prognostication, with the non-invasive nature of AIS explaining its substantially better outcomes.
- A multidisciplinary team approach, comprising radiologists, nuclear medicine specialists, surgeons, pulmonologists, and cancer specialists, is recommended for the management of patients with pulmonary nodules, including those with AIS and invasive adenocarcinoma 1.
From the Research
Pulmonary Adenocarcinoma vs Pulmonary Adenocarcinoma In Situ
- Pulmonary adenocarcinoma is the most common and diverse form of primary lung carcinoma, with a complex histology that poses problems for pathologists 2.
- The current WHO classification of pulmonary adenocarcinoma does not adequately address clinically relevant biological factors, making accurate diagnosis on small biopsy specimens challenging 2.
- Tumors showing a pure bronchioloalveolar (BAC) pattern are now considered adenocarcinoma-in-situ, while invasive adenocarcinomas may also show elements with the BAC pattern, indicating a better prognosis but not necessarily in-situ disease 2.
Treatment and Outcomes
- Segmentectomy and lobectomy are two surgical treatments for pulmonary adenocarcinoma, with studies suggesting that segmentectomy can achieve similar recurrence-free and overall survival rates compared to lobectomy for patients with clinical N0 invasive lung adenocarcinomas of no more than 2 cm 3, 4, 5.
- Propensity score matching has been used to compare survival outcomes between segmentectomy and lobectomy, with results showing no significant difference in overall survival or recurrence-free survival between the two groups 3, 4, 5.
- Segmentectomy may be considered an alternative approach for patients with clinical stage IA adenocarcinoma, especially for those with limited respiratory function or higher ASA scores 4, 6.
Patient Selection and Outcomes
- Patient selection criteria for segmentectomy versus lobectomy include factors such as age, tumor size, SUVmax, and respiratory function, with segmentectomy often preferred for "compromised" patients with limited respiratory function or higher ASA scores 6.
- Studies have shown that segmentectomy can have lower complication rates and similar short-term outcomes compared to lobectomy, making it a valid alternative for selected patients 6.