October 2026 Oncology Roundup: New Approvals, Trial Findings Inform Treatment Decisions

October’s oncology developments expanded treatment options while raising important questions about how therapies should be delivered. New FDA approvals introduced an immunotherapy approach for selected patients with locally advanced rectal cancer and expanded targeted combinations in metastatic breast and prostate cancers. Meanwhile, trial findings provided longer-term evidence for adjuvant ribociclib (Kisqali; Novartis) and cautioned against extending immunotherapy intervals without supporting data.^1-5

These 5 updates from Pharmacy Times highlight developments relevant to treatment selection and pharmacist-led medication management.

Dostarlimab Offers an Immunotherapy Approach for Locally Advanced Rectal Cancer

The FDA’s October 19, 2026, accelerated approval of dostarlimab-gxly for MSI-H/dMMR locally advanced rectal cancer introduced a new option for adults with stage II or III disease. Eligibility requires microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) tumors identified through an FDA-authorized test.¹

The approval offers some patients the possibility of avoiding chemotherapy, radiation, and surgery. However, the accelerated pathway and evolving response data make continued follow-up essential. The long-term risk of relapse remains uncertain, and clinical complete response should not be interpreted as eliminating surveillance requirements.¹

For pharmacists, implementation includes confirming biomarker-defined eligibility and counseling about immune-mediated adverse reactions. Monitoring remains relevant after treatment ends because these reactions can emerge during or following checkpoint inhibitor therapy.¹

Tucatinib Expands HER2-Positive Breast Cancer Maintenance Treatment

The approval of tucatinib (Tukysa; Seagen, Inc, Pfizer) with trastuzumab and pertuzumab for maintenance treatment added an oral targeted therapy option for adults with unresectable locally advanced or metastatic HER2-positive breast cancer following induction treatment.²

In HER2CLIMB-05, median progression-free survival (PFS) reached 24.9 months with tucatinib compared with 16.3 months with placebo, each administered with trastuzumab and pertuzumab (hazard ratio [HR], 0.64; 95% CI, 0.51–0.80). Overall survival (OS) data were immature, so a survival advantage had not been established.²

Pharmacy teams should distinguish this maintenance combination from tucatinib’s regimen with trastuzumab and capecitabine. The updated boxed warning for hepatotoxicity also makes liver monitoring and careful management of treatment interruptions particularly important.²

Talazoparib Plus Enzalutamide Moves Into Earlier Metastatic Prostate Cancer

On October 26, 2026, the FDA expanded approval of talazoparib (Talzenna; Pfizer) plus enzalutamide (Xtandi; Astellas, Pfizer) for HRR-mutated metastatic prostate cancer in adults with metastatic androgen pathway modulation-naïve or -sensitive disease. Qualifying homologous recombination repair (HRR) gene mutations must be detected by an FDA-authorized test.³

The decision followed TALAPRO-3 (NCT04821622), which enrolled 599 patients and demonstrated improved radiographic PFS with the combination versus enzalutamide plus placebo. Median radiographic PFS was not reached with talazoparib compared with 45.8 months in the control group (HR, 0.48; 95% CI, 0.36–0.65). OS data remained immature.³

The approval increases the importance of molecular testing before treatment selection. Pharmacists can help verify eligibility and support ongoing androgen deprivation therapy, while monitoring for myelosuppression and reviewing the precautions associated with PARP inhibitor treatment.³

NATALEE Adds 6-Year Survival Evidence for Adjuvant Ribociclib

Six-year findings from NATALEE provided additional evidence for ribociclib plus a nonsteroidal aromatase inhibitor in high-risk hormone receptor-positive, HER2-negative early breast cancer.⁴

The analysis reported an OS HR of 0.809 (95% CI, 0.661–0.989), representing a 19.1% relative reduction in the risk of death. The estimated absolute OS difference at 6 years was 2.1 percentage points. The OS analysis was prespecified and descriptive, an important qualification when discussing the findings.⁴

For pharmacists counseling patients about extended adjuvant treatment, the results provide context for discussing anticipated benefits. They also reinforce the importance of explaining relative versus absolute effects and supporting treatment persistence through appropriate toxicity management.⁴

MOIO Raises Concerns About Every-12-Week Immunotherapy

The phase 3 MOIO trial (NCT05078047) examined whether patients responding to immune checkpoint inhibitors could receive the same dose every 12 weeks instead of continuing standard-frequency treatment. The strategy failed to establish PFS noninferiority and raised OS concerns without a meaningful safety advantage.⁵

Median PFS was 25.0 months with standard dosing and 21.9 months with reduced-frequency dosing. Deaths occurred in 10.5% and 19.9% of patients, respectively, contributing to early stopping. Although the interim findings did not formally establish definitive inferiority, they do not support routine adoption of the tested schedule.⁵

For pharmacists, the distinction between extending an interval alone and using an established alternative dose-and-interval combination is critical. MOIO’s findings should not be generalized to approved extended-interval schedules that adjust the administered dose.⁵

REFERENCES

1. McGovern G. Dostarlimab receives FDA accelerated approval for MSI-H/dMMR locally advanced rectal cancer. Pharmacy Times. October 19, 2026. Accessed October 30, 2026. https://www.pharmacytimes.com/view/dostarlimab-receives-fda-accelerated-approval-for-msi-h-dmmr-locally-advanced-rectal-cancer

2. Kariyawasam-Chavez R. Tucatinib moves into breast cancer maintenance. What changes for pharmacists? Pharmacy Times. October 20, 2026. Accessed October 30, 2026. https://www.pharmacytimes.com/view/tucatinib-moves-into-breast-cancer-maintenance-what-changes-for-pharmacists-

3. Kariyawasam-Chavez R. FDA approves talazoparib with enzalutamide for HRR-mutated metastatic prostate cancer. Pharmacy Times. October 26, 2026. Accessed October 30, 2026. fda-approves-talazoparib-with-enzalutamide-for-hrr-mutated-metastatic-prostate-cancer

4. Kariyawasam-Chavez R. Ribociclib shows overall survival benefit at 6 years in NATALEE breast cancer trial. Pharmacy Times. October 27, 2026. Accessed October 30, 2026. https://www.pharmacytimes.com/view/ribociclib-shows-overall-survival-benefit-at-6-years-in-natalee-breast-cancer-trial

5. Kariyawasam-Chavez R. MOIO trial raises survival concerns with reduced-frequency immunotherapy. Pharmacy Times. October 28, 2026. Accessed October 30, 2026. moio-trial-raises-survival-concerns-with-reduced-frequency-immunotherapy