The effectiveness of targeted therapies with tyrosine kinase inhibitors in NSCLC depends on the accurate determination of the genomic status of tumor cells. For this reason, molecular analyses to detect genetic rearrangements in some genes is widely recommended by guidelines in patients with advanced NSCLC (53).
In particular, the identification of ROS1 rearrangement in NSCLC patients is mandatory to permit targeted therapy with specific inhibitors, demonstrating an improved overall survival when compared with conventional chemotherapy (1, 6, 7). Treatment of ROS1-positive NSCLC patients with crizotinib has demonstrated a clinically significant benefit (with more than 19 and 51 months of PFS and OS, respectively), and the benefit of other targeted therapies, such as entrectinib are being studied (1, 10).
The availability of specific inhibitors of ROS1 and their clinical benefit should lead to test ROS1 rearrangement simultaneously with EGFR mutation and ALK rearrangement in all advanced stage never/light smokers with squamous cell carcinoma and non-squamous NSCLC (6). However, according to the analysis carried out by Salas et al. (2021) (15) in Spain in 2018, despite the relatively high testing rate reported in EGFR and ALK in NSCLC (91.4% and 80.1%, respectively), the real-world evidence obtained from the LungPath registry demonstrates that ROS1 and PD-L1 were not determined in a significant portion of patients (56.2% and 58.1%, respectively) (15). Based on these authors, the fact that the determination of ROS1 is not always performed in Spain is probably because the determination in some laboratories is sequential, and there is not enough sample material or samples were of poor quality containing insufficient tumor amount to determine all biomarkers (15).
Given the incremental importance of ROS1 testing in guiding the treatment of patients with NSCLC and the fact that ROS1 is an under-analyzed biomarker in comparison to ALK or EGFR in Spain (15), the main objective of our study was to assess if testing ROS1 is a cost-effectiveness strategy in Spain and also to raise the awareness of testing ROS1 according the clinical guidelines.
Our study is the first one that evaluate the efficiency of ROS1 determination in the management of patients with advanced NSCLC in Spain using an approach that integrates molecular diagnosis with subsequent pharmacological treatment.
Markov models allowed the calculation of long-term costs, LYs and QALYs for each treatment assigned according to the molecular diagnosis. In addition, the sequential decision-tree allowed comparison of the ROS1 testing strategy vs. no ROS1 testing strategy in Spain (EGFR, ALK and PD-L1 expression were tested in both strategies) and establish the subsequent treatment allocation according to the molecular diagnosis.
Thus, the ICUR obtained (for the base case and sensitivity analyses) demonstrates that the testing ROS1 strategy in patients with advanced NSCLC is a cost-effective strategy as it is below the cost-effectiveness thresholds usually considered in our country (51, 52).
Given that soon entrectinib will be available for ROS1-positive patients as a first-line targeted therapy (currently the only existing treatment is crizotinib), the sensitivity analysis also included entrectinib as a possible treatment for these patients. In this alternative scenario, the strategy of testing ROS1 vs. no testing is also remained as a cost-effective strategy (with a lower ICUR than in the base case). On the other hand, in a scenario that could be closer to real-world practice than the base case, which considers the accuracy of molecular diagnostic techniques, ROS1 testing strategy is shown to be dominant over no-ROS1 testing, with an increase in QALYs at a lower cost. However, given the uncertainty associated with the specificity and sensitivity parameters of the determination techniques, the results of this alternative scenario must be interpreted with caution.
Despite the low prevalence of ROS1 rearrangements in patients with advanced NSCLC (~1%), these results confirm that ROS1 testing is of crucial interest for the treatment of patients with advanced NSCLC (1, 6).
Prior to this joint model, the same group of experts developed a similar one to determine the efficiency of management of patients with advanced NSCLC in Spain but focusing on ALK detection (23). Although both joint models have in common the integration of molecular diagnosis and subsequent treatment depending on the molecular results, they have also some methodological differences. First, the current work analyses the determination of ROS1 within the EGFR, ALK, ROS1 and PD-L1 sequence. In contrast, the previous study focused exclusively on the determination of ALK, and although it included other biomarkers, these were analyzed following ALK testing. In addition, the previous work considered the different ALK testing techniques and their accuracy (specificity and sensitivity), as the objective was to evaluate the current ALK testing scenario. In the present analysis, we focused on whether or not ROS1 was tested, so the accuracy of the ROS1 techniques was assessed only as an alternative scenario. According to the results of both studies, the strategies of testing ALK and ROS1 vs. no testing, not only generate more than 3,000 QALYs and 120 QALYs, respectively, and remain cost-effective strategies in the Spanish context (€ 10,142 /QALY and € 18.514 /QALY, respectively) (23).
No other studies that analyze specifically the implications of ROS1 determination in our European context have been identified. However, in a broader context, recent studies have reported on the factors that most affect the biomarker determination value such as that conducted by Safonov et al. (2016) in the United States, and also the cost-effectiveness of different NSCLC biomarker testing strategies including ROS1 among them, as the study carried out by Schluckebier et al. (2020) from the Brazilian health system perspective (54, 55).
Like all theoretical models, our study has several limitations. Firstly, the complexity of clinical practice cannot be fully captured by pharmacoeconomic models which are designs with a certain degree of intrinsic structural rigidity. In this particular case, capturing and reproducing all phases of pathological and molecular diagnostics is complicated by the fact that, according to the studies identified, they have a high degree of complexity and variation between centers. In line with the previous study focusing on ALK determination, to simplify the model the pre-analytical phase (e.g. response time from diagnosis to initiation of treatment) was not included as there is no evidence that it influences the results.
Certain assumptions have been made to model the treatment of invalid results and the probability of re-biopsy in the diagnostic phase. To simplify the model, it was assumed that after an invalid result there is no repetition of the technique using the same sample, but re-biopsy is considered directly. This assumption was made because, according to expert opinion, repeat testing on the same sample is rarely satisfactory and recoverable tests accounts for less than 10%. Regarding the success rate of re-biopsy, no reference was identified in the literature that according to the experts is in line with their clinical experience, where in 30-35% of cases an optimal re-biopsy specimen is achieved. Thirdly, since the main objective of the analysis was to determine the significance of ROS1 determination and not so much the validation of the testing techniques, a specificity and sensitivity of the techniques of 100% was assumed and validated by experts, which is far from real clinical practice. However, this limitation was evaluated in one of the alternative scenarios.
Fourth, Markov models have some limitations when reproducing at a long term the clinical management of NSCLC patients. On the one hand, as in all cost-effectiveness models where long-time horizons are used, extrapolations are necessary with the associated limitations. On the other hand, as described above, in the absence of individualized data for all treatments included in the analysis, it was assumed the use of exponential models for all treatments, as conducted in Nadal. et al. (2021) (23). As our analysis focuses on molecular diagnosis and subsequent first-line treatment of NSCLC patients, the second-line treatment included in the analysis was entered into the model as a one-off cost and only shows its influence in economic terms.
Fifthly, and in relation to costs, it is difficult to establish the real price of the diagnostic tests and although these were validated by experts, there are large variations between centers and in many cases, as they are not reimbursed by the Spanish NHS, the cost of the tests is mainly assumed by the pharmaceutical companies and research funds in the vast majority of Spanish regions. On the other hand, the fact that the model assumed a sequential determination and that it focused on the determination of ROS1 did not allow us to capture the benefits of using NGS as a technique to evaluate multiple biomarkers simultaneously. An economic assessment of the use of NGS instead of sequential ROS1 testing in addition to EGFR and ALK will require a specifically designed model and is beyond the scope of this study.
Despite these limitations and the associated uncertainty, sensitivity analyses were carried out which confirmed the robustness of the assumptions and results obtained. It should also be noted that the panel of experts validated all the assumptions, parameters considered, and results obtained.