September 2026 in Oncology: 5 Updates on Treatment Options and Patient Care

September 2026 brought oncology developments with implications for both treatment selection and the practical delivery of care. New oral combinations expanded options after disease progression, while lung cancer label updates addressed response durability and the time patients spend under observation.

For oncology pharmacists, these changes affect how regimens are reviewed, how patients are counseled, and how treatment teams coordinate follow-up. Emerging research also sharpened questions about antibiotic stewardship during cellular therapy. Here are 5 updates from September’s Pharmacy Times coverage worth revisiting.

1. Imlunestrant Plus Abemaciclib Expands Options for ESR1-Mutated Breast Cancer

The FDA approved imlunestrant (Inluriyo; Eli Lilly and Company) with abemaciclib (Verzenio; Eli Lilly and Company) for adults with estrogen receptor–positive, HER2-negative, ESR1-mutated locally advanced or metastatic breast cancer that progressed after at least 1 line of endocrine therapy. Eligibility requires confirmation of the mutation with an FDA-authorized test.¹

In the ESR1-mutated subgroup of the phase 3 EMBER-3 trial, median progression-free survival (PFS) was 11.1 months with the combination compared with 5.5 months with imlunestrant alone (hazard ratio [HR], 0.53; 95% CI, 0.35-0.80).¹

The oral regimen brings familiar but substantial monitoring responsibilities. Pharmacists should reinforce early diarrhea management and review blood count and liver function monitoring while checking concomitant medications for interactions.¹

2. Belzutifan Plus Lenvatinib Gains Approval After Immunotherapy in Kidney Cancer

On September 24, the FDA approved belzutifan (Welireg; Merck) with lenvatinib (Lenvima; Eisai) for adults with advanced renal cell carcinoma with a clear cell component following a PD-1 or PD-L1 inhibitor.²

The phase 3 LITESPARK-011 trial enrolled 747 patients. Median PFS reached 14.6 months with the combination compared with 10.6 months with cabozantinib (HR, 0.74; 95% CI, 0.61-0.89). Objective response rates were 53% and 40%, respectively. The final overall survival analysis did not demonstrate a statistically significant difference.²

The all-oral regimen requires attention to overlapping treatment burdens. Belzutifan-associated anemia and hypoxia warrant monitoring, while lenvatinib adds concerns such as hypertension and proteinuria. Medication review and adherence support remain central to implementation.²

3. Tarlatamab Label Update Shortens Initial Monitoring

An FDA-approved prescribing information update reduced recommended monitoring for the first 2 tarlatamab-dlle (Imdelltra; Amgen) infusions from 22 to 24 hours to 6 to 8 hours from the start of infusion. Patients also require a follow-up assessment, including vital signs, the next day after each of those doses.³

Tarlatamab is indicated for adults with extensive-stage small cell lung cancer progressing on or after platinum-based chemotherapy. The shorter observation period could make initial administration more feasible in community oncology settings.³

The update preserves the need for step-up dosing and vigilance for cytokine release syndrome and neurologic toxicity. Patients should remain within 1 hour of an appropriate health care setting for 48 hours after the first 2 infusions, accompanied by a caregiver.³

4. Taletrectinib Label Adds Longer-Term Response Data in ROS1-Positive NSCLC

The FDA approved a supplemental application updating taletrectinib (Ibtrozi; Nuvation Bio) labeling with longer-term efficacy findings in tyrosine kinase inhibitor–naïve patients with advanced ROS1-positive non–small cell lung cancer (NSCLC). Taletrectinib originally received FDA approval in June 2025; September’s action updated the evidence supporting its use.⁴

In TRUST-I, the median duration of response reached 49.7 months among TKI-naïve patients, with a median follow-up of 51 months. The update did not introduce new safety signals or change the safety sections of labeling.⁴

The findings provide additional context for counseling about sustained treatment. Pharmacists should continue reviewing adherence and monitoring for established toxicities, including hepatotoxicity and QTc prolongation, throughout prolonged oral therapy.⁴

5. CAR T-Cell Coverage Highlights the Importance of Antibiotic Stewardship

September coverage from the International Myeloma Society meeting renewed attention to the relationship between the gut microbiome and CAR T-cell outcomes. Supporting evidence includes a 2022 multicenter study of anti-CD19 CAR T-cell recipients with B-cell malignancies. In its retrospective cohort of 228 patients, exposure to piperacillin-tazobactam, meropenem, or imipenem-cilastatin in the 4 weeks before treatment was associated with worse survival and increased neurotoxicity.^5,6

The findings reinforce the value of reviewing antibiotic selection and duration during cellular therapy, with attention to the effects of broad-spectrum agents on the gut microbiome.⁵

These associations require careful interpretation and do not establish that changing antibiotics improves outcomes in every patient. Infection treatment must remain appropriate to the clinical situation. Prospective studies are needed to determine whether microbiome-preserving strategies can improve CAR T-cell efficacy without compromising infection management.⁵

REFERENCES

1. Halpern L. FDA approves imlunestrant, abemaciclib combo for ESR1+ metastatic breast cancer. Pharmacy Times. Published September 21, 2026. Accessed September 30, 2026. https://www.pharmacytimes.com/view/fda-approves-imlunestrant-abemaciclib-combo-for-esr1-metastatic-breast-cancer

2. Ferruggia K. FDA approves belzutifan plus levatinib for advanced renal cell carcinoma after immunotherapy. Pharmacy Times. Published September 24, 2026. Accessed September 30, 2026. https://www.pharmacytimes.com/view/fda-approves-belzutifan-plus-lenvatinib-for-advanced-renal-cell-carcinoma-after-immunotherapy

3. Halpern L. FDA reduces monitoring time for first two tarlatamab doses. Pharmacy Times. Published September 17, 2026. Accessed September 30, 2026. https://www.pharmacytimes.com/view/fda-reduces-monitoring-time-for-first-two-tarlatamab-doses

4. McGovern G. FDA grants approval to sNDA to taletrectinib in advanced ROS1+ NSCLC. Pharmacy Times. Published September 17, 2026. Accessed September 30, 2026. https://www.pharmacytimes.com/view/fda-grants-approval-to-taletrectinib-for-advanced-ros1-nsclc

5. Gerlach A. Harnessing the gut microbiome for enhanced CAR T-cell therapy. Pharmacy Times. Published September 24, 2026. Accessed September 30, 2026. https://www.pharmacytimes.com/view/harnessing-the-gut-microbiome-for-enhanced-car-t-cell-therapy

6. Smith M, Dai A, Ghilardi G, et al. Gut microbiome correlates of response and toxicity following anti-CD19 CAR T cell therapy. Nat Med. 2022;28(4):713-723. doi:10.1038/s41591-022-01702-9