The new second-line playbook after platinum-based therapy in relapsed SCLC

By Naveed Saleh, MD, MSFact-checked by Barbara BekieszPublished March 17, 2026

Key Takeaways

Platinum sensitivity is no longer the main decision driver, per the recent NCCN guideline update: Treatment selection has shifted away from strict 6-month cutoffs toward clinician judgment and emerging trial data.
In platinum-sensitive relapse, retreatment improves PFS vs topotecan (3.9 vs 2.7 months), yet many clinicians are skipping this evidence-based option.
Options remain limited in platinum-resistant SCLC, but lurbinectedin expands the toolbox, offering a meaningful alternative with ~35% response in sensitive disease and FDA approval post-first line progression.

Small-cell lung cancer (SCLC) is the most aggressive form of lung cancer, and although initially responsive to chemotherapy—and sensitive to radiotherapy—resistance soon develops. The result is a 5-year survival rate of <10%.^[]

The crucial factor guiding second-line treatment in the relapsed setting is whether the tumor is platinum-sensitive or platinum-resistant. Although this distinction is emphasized in treatment guidelines, real-world treatment patterns indicate that this consideration is not applied consistently in clinical practice.

“This treatment strategy is not as commonly used in the second line in the modern treatment landscape that includes tarlatamab,” said Jessica Ross, MD, thoracic medical oncologist and early drug development specialist at Memorial Sloan Kettering Cancer Center (MSKCC), in an exclusive interview with MDLinx.

Taken together, the challenge now is knowing how to apply platinum sensitivity in a treatment landscape that’s rapidly evolving beyond this traditional framework.

Step 1: Determine platinum sensitivity

The definition of platinum sensitivity has generally been based on the length of the treatment-free interval following this therapy. “Platinum sensitivity has been variably described as a chemotherapy-free interval of 3 to 6 months,” Dr. Ross explains.

In fact, the 2022 guidelines from the National Comprehensive Cancer Network (NCCN) honed in on 6 months as the treatment-free interval cut-off for sensitive SCLC and fewer than 6 months for resistant SCLC.^[] NCCN noted that, regardless of treatment-free interval, the response rate for platinum-resistant disease was ≤10% compared with ≈25% for platinum-sensitive disease.^[]

However, the most recent 2026 update of the NCCN guidelines no longer bases treatment recommendations on the treatment-free interval. Instead, the guidelines advise that subsequent therapy options for all patients with SCLC should be chosen based on clinical expertise and trial data.^[]

Step 2: Treat platinum-sensitive tumors

In patients with platinum-sensitive disease, specialists can re-challenge using the original platinum.

In an open-label, randomized, phase 3 trial, French researchers found that in ES-SCLC patients receiving second-line treatment, progression-free survival (PFS) was longer in the combination chemotherapy arm (carboplatin plus etoposide) than in the topotecan arm, or 3.9 months vs 2.7 months, respectively.

Despite the efficacy of chemotherapy, many oncologists forego re-challenge in favor of single-agent options like tarlatamab.

“Tarlatamab is a bispecific T cell engager that binds to DLL3 on tumor cells and CD3 on T cells, bringing the immune system to the cancer,” says Dr. Ross. She points to results of the DeLLphi-304 study, which established that tarlatamab was associated with a longer overall survival (OS) and progression-free survival (PFS) than achieved with investigator’s choice of chemotherapy.^[]

“Although platinum retrial was not allowed in the control arm, the study established the superiority of tarlatamab over other chemotherapies,” Dr. Ross explains. “Overall, I think when tarlatamab is available, I’d reach for that over a platinum retrial because it offers a novel mechanism of action.”

Step 3: Treat platinum-resistant tumors

Options for patients resistant to platinum are limited.

Historically, topotecan has been the standard second-line therapy based on randomized trials demonstrating survival benefit compared with best supportive care.

For instance, results of a 2006 Phase 3 trial indicated that in the intent-to-treat population, median OS with best supportive care was 13.9 weeks vs 25.9 weeks with topotecan.^[]

More recently, lurbinectedin has emerged as an alternative option, demonstrating an overall response rate of approximately 35% in platinum-sensitive disease, a median PFS of 3.5 months, and a median OS of 9.3 months.^[]^[] These encouraging trial results led to the FDA's accelarated approval of lurbinectedin (Zepzelca) for progression of metastatic SCLC after first-line chemotherapy.

Step 4: Sequencing

As a last resort, oncologists can consider molecular sequencing of the cancer in an effort to discover vulnerable targets.

Data from human tumors, cancer cell lines, patient-derived xenografts, and genetically engineered mouse models appear to be centering on a novel model of SCLC subtypes defined by the differential expression of four key transcription regulators: ASCL1, NeuroD, YAP1, and POU2F3.^[]

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