Understanding Radiographic Progression and Response Assessment in Cancer Treatment

Understanding Radiographic Progression and Response Assessment in Cancer Treatment

Introduction:
In the ever-evolving field of oncology, the accurate assessment of treatment response and disease progression is crucial for guiding treatment decisions. Two recent studies, ASCO 2022's analysis of ARCHES and ASCO GU 2020's exploration of challenging scenarios in renal cell carcinoma (RCC) management, shed light on the complexities of radiographic progression and response assessment in cancer patients. By examining the findings of these studies, we can gain valuable insights into the discordance between radiographic progression and PSA progression, as well as the unique phenomena of hyperprogression and pseudoprogression. Let's delve deeper into these topics and understand their implications.

Radiographic Progression vs. PSA Progression:
The post hoc analysis of ARCHES revealed a frequent discordance between radiographic progression and PSA progression in patients with metastatic hormone-sensitive prostate cancer (mHSPC) treated with enzalutamide and androgen deprivation therapy (ADT). The PCWG2 criteria, as well as any rise in PSA levels over nadir, were used to define PSA progression. However, despite meeting these criteria, some patients did not exhibit radiographic progression. This raises questions about the reliability of PSA as a sole marker for disease progression and emphasizes the importance of incorporating radiographic assessment into treatment decisions.

Unique Phenomena in RCC Treatment:
The ASCO GU 2020 study focused on challenging clinical scenarios in the management of RCC, particularly highlighting the complexities of response assessment in patients receiving immunotherapy. Unlike traditional chemotherapy, immunotherapy can lead to delayed responses, making accurate assessment of response or progression a challenge. The study suggests that two consecutive follow-up imaging studies, performed at least four weeks apart, should be used to evaluate response or progression accurately. Hyperprogression, a distinct phenomenon observed in RCC and other solid tumors treated with immune checkpoint inhibitors, involves a rapid increase in tumor growth rate. This phenomenon underscores the need for careful monitoring and prompt intervention when hyperprogression is detected. Additionally, new lesions may appear as a result of the immune cell infiltration and growth of initially undetectable micrometastatic disease, emphasizing the importance of post-treatment imaging in detecting these emerging lesions. Pseudoprogression, characterized by immune cell infiltration of the tumor with or without edema, further complicates response assessment. These unique aspects of RCC treatment highlight the limitations of traditional response assessment criteria, such as RECIST 1.1, and call for the adoption of more comprehensive frameworks like iRECIST.

Insights and Actionable Advice:
Combining the findings from these studies, we can glean several insights and actionable advice for clinicians and researchers:

1. Rethinking Response Assessment: The discordance between radiographic progression and PSA progression in mHSPC patients suggests the need for a more comprehensive approach to response assessment. Integrating radiographic imaging alongside PSA measurements can provide a more accurate picture of disease progression and guide treatment decisions accordingly.

2. Vigilance in Immunotherapy: Given the potential for delayed responses, clinicians must remain vigilant when evaluating treatment outcomes in patients receiving immunotherapy. Employing the recommended approach of two consecutive follow-up imaging studies, performed at least four weeks apart, can help minimize the risk of misinterpreting response or progression.

3. Adapting Response Assessment Criteria: The unique phenomena of hyperprogression and pseudoprogression observed in RCC treatment highlight the limitations of traditional response assessment criteria like RECIST 1.1. The adoption of more comprehensive frameworks like iRECIST, which consider immune cell infiltration and other factors, can provide a more accurate assessment of treatment response and guide therapeutic decisions.

Conclusion:
As the field of oncology continues to advance, it is crucial to stay informed about the complexities of radiographic progression and response assessment in cancer treatment. The studies discussed in this article shed light on the challenges faced by clinicians and researchers, and offer valuable insights for improving patient care. By rethinking response assessment, remaining vigilant in immunotherapy cases, and adapting assessment criteria, we can enhance our ability to accurately evaluate treatment outcomes and make informed decisions for our patients.