What is the optimal timing for imaging after concurrent chemoradiotherapy (chemoRT) prior to initiating durvalumab (durvalumab) for stage III non-small cell lung cancer?

Optimal Timing for Imaging After Concurrent Chemoradiotherapy Prior to Durvalumab

Imaging must be performed within 4-6 weeks after completing concurrent chemoradiotherapy to confirm absence of disease progression before initiating durvalumab, which should be started 1 to 42 days after completing radiation. 1, 2

Critical Window for Durvalumab Initiation

• Durvalumab must be started between 1 and 42 days after completing thoracic radiation therapy, as established in the PACIFIC trial protocol and FDA labeling 2, 3
• This narrow therapeutic window necessitates prompt post-treatment imaging assessment, typically within 4-6 weeks of completing radiation, to avoid missing the opportunity for consolidation therapy 1
• The median time to durvalumab initiation in real-world practice is approximately 57 days (range 12-99 days) from end of radiotherapy, though earlier initiation within the 42-day window is preferred 4

Pre-Durvalumab Imaging Requirements

• Contrast-enhanced chest CT scan is the primary imaging modality required to document stable disease or response before durvalumab initiation 1
• Imaging must confirm no disease progression per RECIST v1.1 criteria, as progression following concurrent chemoradiotherapy is an exclusion criterion for durvalumab consolidation 2, 3
• Brain imaging (contrast-enhanced MRI preferred, or CT if MRI unavailable) should be performed if neurological symptoms develop or if there is clinical suspicion of intracranial disease 5, 1

Ongoing Surveillance Schedule During Durvalumab

• Tumor assessment should be performed every 8 weeks during the 12-month durvalumab consolidation period using contrast-enhanced chest CT 2
• After completing durvalumab, surveillance visits every 6 months for the first 2 years are recommended, including history, physical examination, and preferably contrast-enhanced volume chest CT scan at minimum at 12 and 24 months 5, 1
• Following the initial 2-year period, transition to annual visits with chest CT scan to detect second primary tumors or late relapse 5, 1

Common Pitfalls to Avoid

• Delaying initial post-treatment imaging beyond 6-8 weeks may miss the 42-day window for durvalumab consolidation, which has demonstrated significant survival benefit with median overall survival of 47.5 months versus 29.1 months with placebo 1, 6
• Relying solely on clinical assessment without imaging may miss asymptomatic progression, as approximately 27-35% of patients will have disease progression within 5-6 months after chemoradiotherapy without consolidation therapy 3
• PET-CT should be used cautiously for pre-durvalumab assessment due to high false-positive rates from post-radiation inflammation, and biopsy confirmation should be obtained whenever possible if salvage therapy is being considered 5
• Patients with documented disease progression following concurrent chemoradiotherapy are ineligible for durvalumab consolidation and should not receive this therapy 2, 3

Special Considerations for Sequential Chemoradiotherapy

• For patients who received sequential rather than concurrent chemoradiotherapy, the same imaging timeline applies, with durvalumab initiated 1-42 days after completing radiotherapy 7
• The PACIFIC-6 trial demonstrated that durvalumab after sequential chemoradiotherapy is well tolerated with median progression-free survival of 13.1 months, supporting this approach when concurrent therapy is not feasible 7