Adjuvant PD-1/PD-L1 Inhibitors Show Benefit in Solid Tumors but Raise Safety Considerations

Tumor immune checkpoint inhibitors, such as those targeting PD-1 and PD-L1, represent a major breakthrough in the treatment of advanced cancers. More recently, these agents have also been integrated into the adjuvant setting, meaning the treatment is given post surgery to prevent cancer recurrence.

A recent systematic review and meta-analysis published in Oncotarget suggests that these agents provide meaningful clinical benefit in patients with high-risk solid tumors.¹

Adjuvant therapy works by killing residual microscopic disease, which, if left untreated, is the major cause of relapse. Although traditional chemotherapy drugs kill cancer cells directly, PD-1/PD-L1 inhibitors boost the body's natural immune defenses, enabling the immune system to recognize and dispose of the leftover cancer cells. This mode of action has put immunotherapy among the most hopeful tactics to be used in cancer treatment at its early stages.²

Improved Disease-Free Survival With Checkpoint Inhibition

This meta-analysis incorporated 13 randomized controlled trials with a combined sample size of around 10,000 patients with various types of solid tumors, including melanoma, urothelial carcinoma, and gastrointestinal cancers. The data revealed that adjuvant PD-1/PD-L1 inhibitors showed a statistically significant improvement in disease-free survival (DFS) and distant metastasis-free survival relative to placebo or observation.¹

These findings suggest that checkpoint inhibitors not only postpone relapse but also diminish the chances of metastatic spread after surgical interventions. These benefits are stronger in high-risk patients for whom recurrence rates are still high even with the use of standard therapies.^1,3

Although these enhancements were beneficial for early end points, this study did not reveal a consistent overall survival (OS) benefit across tumor types and studies. This inconsistency points to a continuing problem in oncology: Whether improvements in DFS really result in longer-term survival benefits.¹

Heterogeneity in Treatment Response

Variability in treatment effectiveness across tumor types and individual patients is an important factor to consider. Although some cancers—especially melanoma and urothelial cancers—respond very well to adjuvant immunotherapy, other cancers only show limited or variable benefits. Such diversity in response highlights the importance of developing better patient selection methods. Biomarkers including PD-L1 expression, tumor mutational burden, and characteristics of the tumor microenvironment are potential influencers of treatment response. Determining which patients are most likely to benefit from adjuvant PD-1/PD-L1 blockade is an essential area of active investigation.^1,3

Additionally, potential differences between PD-1 and PD-L1 inhibitors in efficacy and safety profiles warrant further investigation, as these distinctions may inform clinical decision-making.

Safety Profile and Clinical Considerations

Although PD-1/PD-L1 inhibitors have proven quite effective, they are associated with an increased risk of treatment-related adverse events (AEs). The meta-analysis showed that these inhibitors lead to a higher incidence of mild adverse effects, including fatigue, itching, and nausea, as well as immune-related endocrine disorders like hypothyroidism.^1,2

Severe immune-related AEs, although less frequent, can involve multiple organ systems and require prompt recognition and management. Previous studies have found that the chances of having grade 3 or even more serious AEs are higher with checkpoint inhibitors than with a placebo, pointing to the fact that these agents should be used under continuous and careful monitoring.³

For pharmacists, these findings highlight a critical role in patient education, early toxicity identification, and coordination of care. Ensuring that patients understand potential AEs and when to seek medical attention is essential to maintaining adherence and minimizing complications.

Conclusion

Adjuvant PD-1/PD-L1 inhibitors represent a major milestone in the treatment of solid tumors, providing improved DFS and metastasis-free survival for high-risk patients. However, the absence of a definitive OS advantage and the potential for greater toxicity highlight the need for personalized treatment decision-making. As studies aimed at identifying the right patients and improving treatment strategies proceed, oncology pharmacists will continue to play a crucial role in monitoring treatment effectiveness and safety as these changes unfold.

REFERENCES

1. Mo DC, Liang ZY, Chen L, Huang JF, Luo PH, Wang HL. Efficacy and safety of adjuvant therapy with PD‑1/PD‑L1 inhibitors in cancer. Exp Ther Med. 2022;24(6):749. doi:10.3892/etm.2022.11685

2. Jin Y, Wei J, Weng Y, et al. Adjuvant therapy with PD-1/PD-L1 inhibitors for human cancers: a systematic review and meta-analysis. Front Oncol. 2022;12:732814. doi:10.3389/fonc.2022.732814

3. Mo DC, Liang ZY, Chen L, Huang JF, Luo PH, Wang HL. Efficacy and safety of adjuvant therapy with PD‑1/PD‑L1 inhibitors in cancer. Exp Ther Med. 2022;24(6):749. doi:10.3892/etm.2022.11685