Does adherence to the diaphragm (DIAPH) change the tumor's prognosis or treatment plan?

Diaphragmatic Tumor Invasion: Impact on Prognosis and Treatment

Diaphragmatic invasion by a tumor significantly impacts both prognosis and treatment planning, with transdiaphragmatic invasion indicating surgical ineligibility and poorer outcomes. 1

Staging Implications

• Diaphragmatic invasion by tumors (particularly malignant pleural mesothelioma) has critical staging implications, as it can determine surgical eligibility 1
• Partial-thickness invasion of the diaphragm is classified as T3 disease, while complete transdiaphragmatic invasion is classified as T4 disease 1
• Transdiaphragmatic transgression is considered a contraindication to surgery in mesothelioma patients 1
• The depth of diaphragmatic involvement significantly affects prognosis - shallow invasion (parietal pleura or subpleural tissue) has better outcomes than deep invasion (muscle or peritoneal infiltration) 2

Diagnostic Challenges

• The diaphragm has a thin curvilinear structure with tissue attenuation similar to tumor tissue, making assessment challenging on CT 1
• Standard CT imaging may not accurately determine the extent of diaphragmatic invasion 1
• MRI (preferably with IV contrast) provides better definition of tumor involvement of the diaphragm than CT 1
• MRI has high specificity and sensitivity for detection of transdiaphragmatic spread, allowing differentiation between T3 and T4 disease 1
• Respiratory dynamic cine MRI can provide useful information for distinguishing between diaphragmatic and para-diaphragmatic tumors 3

Surgical Considerations

• For patients with diaphragmatic invasion, surgical approach depends on the extent of invasion 1
• Partial-thickness invasion may be potentially resectable with either partial or total excision of the affected portion of the diaphragm and placement of a diaphragmatic patch or graft 1
• For lung cancer with diaphragmatic invasion, en bloc resection with wide tumor-free margins offers the best chance for cure 2, 4
• Prosthetic replacement of the diaphragm (rather than primary repair) has been significantly related to better survival in some studies 4
• The 5-year survival rate for patients with completely resected T3N0M0 lung cancer invading the diaphragm is approximately 28.3%, while for T3N1-2M0 it drops to 18.1% 2

Additional Diagnostic Approaches

• Laparoscopy can clarify whether transdiaphragmatic tumor invasion is present when imaging is inconclusive 1
• Bulky tumor in the lower hemithorax often involves and depresses the hemidiaphragm, making it difficult to determine whether T4 or M1 disease is present without additional procedures 1
• Some institutions routinely perform staging laparoscopy, while most use it selectively to supplement information from imaging studies 1

Prognostic Implications

• The 5-year survival for patients with shallow diaphragmatic invasion (parietal pleura or subpleural tissue) is approximately 33%, whereas for deep invasion (muscle or peritoneal infiltration) it drops to 14.3% 2
• Complete surgical resection is critical - the 5-year survival for patients with complete resection of lung cancer invading the diaphragm is 22.6%, while there are typically no 4-year survivors with incomplete resection 2
• Lung cancers with deep diaphragmatic invasion (muscle layer or deeper) have poor outcomes despite technical resectability 2

In conclusion, diaphragmatic invasion significantly alters both the staging and treatment approach for tumors. Accurate assessment of the extent of invasion is crucial, with MRI being the preferred modality when diaphragmatic involvement is suspected. Transdiaphragmatic invasion generally indicates surgical ineligibility and poorer prognosis, while partial-thickness invasion may still be amenable to surgical resection with appropriate reconstruction techniques.