Immunotherapy, Chemotherapy, Radiotherapy and Surgery for Synchronous Oligo-metastatic NSCLC

Non-small cell lung cancer (NSCLC) continues to be the leading cause of cancer-related mortality worldwide. Even with adjustment for age NSCLC is responsible for almost 20% of cancer-related deaths. Recent years have brought tremendous progress in the understanding of the disease, its underlying biology and the development of effective therapies. Traditionally, NSCLC has been treated with surgery, platinum-based chemotherapy or radiotherapy alone or in combination, depending on tumour stage, tolerability of expected side effects and prognosis. Various strategies are currently being pursued in order to increase the patient population that may benefit from immunotherapy and to further improve the outcome of patients with NSCLC.

The CHESS clinical trial is for patients with NSCLC that has progressed to a small number of other parts of the body (oligo-metastatic) and has not been previously treated, or after surgical resection of a single metastasis (central nervous system or adrenal). The trial aims to reduce the risk of systemic progression and thereby improve progression free survival. Participants will receive induction treatment consisting of immunotherapy combined with platinum-based doublet chemotherapy and stereotactic body radiotherapy (SBRT) that will be given to all oligo-metastatic locations. SBRT started early and concurrently with immunotherapy aims at enhancing a postulated immune effect and simultaneously effectively control the macro-metastases.

Preclinical data have shown a strong immune-enhancing effect of radiotherapy, especially when delivered to small volumes, in high-single fraction doses and over a short period of time. Consequently, stereotactic body radiotherapy (SBRT) is currently being intensively investigated as a partner for systemic immunotherapy. Earlier clinical studies generated proof-of-principle data for the synergistic effects of combined radiotherapy and immunotherapy. Chemotherapy and high-dose radiotherapy are well known triggers of immunogenic cell death and are therefore highly promising partners for combination with immunotherapy.

The sub-group of patients with "oligometastatic" disease was originally described by Hellman and Weichselbaum in 1995. In line with this concept, the current NCCN and ESMO guidelines describe that Stage IV NSCLC patients presenting with solitary metastases can be treated with curative intent using local surgery and/or radiotherapy. Local treatment for oligo-metastatic NSCLC has been adopted rapidly in the oncological community and one reason is the progress made in the fields of surgery and radiotherapy, both becoming less toxic (minimally invasive surgery) and simultaneously less toxic and more effective (precision radiotherapy), respectively. SBRT allows treatment of small peripheral primaries and metastases at virtually all anatomical locations with a favourable therapeutic ratio of local tumour control rates \>90% and low rates of toxicity. Simultaneously, minimally invasive surgery for early and locally advanced NSCLC today achieves excellent local tumour control with low rates of toxicity.