Unexpected toxicity of CDK4/6 inhibitor palbociclib and radiotherapy

ESMO-ESTRO framework for assessing the interactions and safety of combining radiotherapy with targeted cancer therapies or immunotherapy

With the emergence of targeted therapies and immunotherapy, various cellular pathways are utilized to improve tumor control and patient survival. In patients receiving these new agents, radiotherapy is commonly applied with both radical and palliative intent. Combining radiotherapy with targeted therapies or immunotherapy may improve treatment outcomes, but may also lead to increased toxicity. High-quality toxicity data and evidence-based guidelines regarding combined therapy are very limited. The present framework, developed by ESMO and ESTRO, explores the main biological effects and interaction mechanisms of radiotherapy combined with targeted agents or immunotherapy. It addresses general clinical factors to take into consideration when deciding on whether and/or how to combine radiotherapy with these agents. Furthermore, it provides pragmatic, biological mechanism-based, clinical considerations for combining radiotherapy with various targeted agents or immunotherapy.

The Evolving Paradigm of Antibody-Drug Conjugates Targeting the ErbB/HER Family of Receptor Tyrosine Kinases

Current therapies targeting the human epidermal growth factor receptor (HER) family, including monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs), are limited by drug resistance and systemic toxicities. Antibody-drug conjugates (ADCs) are one of the most rapidly expanding classes of anti-cancer therapeutics with 13 presently approved by the FDA. Importantly, ADCs represent a promising therapeutic option with the potential to overcome traditional HER-targeted therapy resistance by delivering highly potent cytotoxins specifically to HER-overexpressing cancer cells and exerting both mAb- and payload-mediated antitumor efficacy. The clinical utility of HER-targeted ADCs is exemplified by the immense success of HER2-targeted ADCs including trastuzumab emtansine and trastuzumab deruxtecan. Still, strategies to improve upon existing HER2-targeted ADCs as well as the development of ADCs against other HER family members, particularly EGFR and HER3, are of great interest. To date, no HER4-targeting ADCs have been reported. In this review, we extensively detail clinical-stage EGFR-, HER2-, and HER3-targeting monospecific ADCs as well as novel clinical and pre-clinical bispecific ADCs (bsADCs) directed against this receptor family. We close by discussing nascent trends in the development of HER-targeting ADCs, including novel ADC payloads and HER ligand-targeted ADCs.

Safety and feasibility of CDK4/6 inhibitors treatment combined with radiotherapy in patients with HR-positive/HER2-negative breast cancer. A systematic review and meta-analysis

BACKGROUND AND PURPOSE

The addition of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) to endocrine therapy in hormone receptor-positive (HR+) human epidermal growth factor 2-negative (HER2-) breast cancer has led to practice-changing improvements in overall survival. However, there are conflicting data concerning the safety of CDK4/6i combination with radiotherapy, and no consensus guidelines exist to guide practice. We conducted a meta-analysis to assess the safety and feasibility of CDK4/6i treatment with radiotherapy.

MATERIALS AND METHODS

A comprehensive search was performed in PubMed/MEDLINE, Web of Science, and Scopus, for studies in advanced/metastatic breast cancer receiving CDK4/6i and radiotherapy with the provided safety data on the occurrence of toxicity. The main outcomes were safety (grade 3-5 adverse events), CDK 4/6i dose reduction, and the discontinuation rate due to toxicity.

RESULTS

Fifteen studies comprising 1133 patients with HR+/HER2- breast cancer patients were included. Among them, 617 pts received CDK4/6i and radiotherapy; the median follow-up was 17.0 months (IQR 9.2 - 18.0), and the median age was 58.8 years (IQR 55.5---62.5). The pooled prevalence of severe hematologic toxicity was 29.4% (95% CI 14.0% - 47.4%; I2 = 93%; τ2 = 0.084; p < 0.01 and severe non-hematologic toxicity was 2.8% (95% CI 1.1% - 4.8%; I2 = 0%; τ2 = 0.0; p = 0.67). The pooled prevalence of CDK4/6i dose reduction was 24.0% (95% CI 11.1% - 39.4%; I2 = 90%; τ2 = 0.052; p < 0.01) with no difference between CDK4/6i plus RT vs. CDK4/6i (odds ratio of 0.934; 95% CI 0.66 - 1.33; I2 = 0%; τ2 = 0.0; p = 0.56). The pooled prevalence of CDK4/6i discontinuation due to toxicity was 2.3% (95% CI 0.4% - 5.2%; I2 = 23%; τ2 = 0.002; p = 0.24).

CONCLUSION

The findings of this study suggest that radiotherapy in addition to CDK4/6i treatment in breast cancer patients is generally safe and well tolerated and remains a viable treatment option.