2.1. Study Design and Data Sources

In this study, interrupted time-series (ITS) analysis was used to study the real data of clinical drug use before and after the seventh round of NCDP intervention in Inner Mongolia. We set the timing of our policy initiation to December 2022. The interrupted time-series analysis (ITS) is a statistical method utilized for assessing the impact of large-scale health interventions. It assesses the intervention’s effect by comparing changes in both the level and trend of time-series data before and after the implementation. Therefore, this study used interrupted time-series analysis to quantitatively evaluate the impact of the seventh round of NCDP on the volume, amount, and daily cost of three targeted antitumor drugs.

Data used in this study were obtained from the People’s Hospital of Inner Mongolia Autonomous Region, Inner Mongolia Cancer Hospital, and the Affiliated Hospital of Inner Mongolia Medical University from January 1, 2022 to June 30, 2023.

The Inner Mongolia Cancer Hospital is a specialized facility for tumor treatment, while the Affiliated Hospital of Inner Mongolia Medical University and Inner Mongolia People’s Hospital are two large comprehensive medical centers. The medication structure of cancer patients in the region can be effectively represented by these three hospitals.

The three targeted antitumor drugs are (1) afatinib dimaleate tablets 30 mg, (2) afatinib dimaleate tablets 40 mg, and (3) sunitinib malate capsules 12.5 mg.

The manufacturers of the bid-winning antitumor drugs are shown in Table 1. Among the targeted antitumor drugs used in the three research institutions in this study, the bid-winning drugs were all generic-targeted antitumor drugs, and the nonwinning drugs were original-targeted antitumor drugs. In the following articles, the utilization of both original and generic versions of targeted antitumor drugs is described.

2.2. Outcome Variables

2.3. Statistical Analysis

Descriptive statistics were used. We first described the change of volume, expenditures, and DDDc of the included original and generic drugs in the corresponding period before and after the implementation of the NCDP policy.

3.1. The Change of Volume, Expenditures, and DDDc

Table 2 shows the changes in the volume, expenditure, and DDDc of the three generic- and original-targeted antitumor drugs prior to and after the implementation of the seventh round of NCDP. Following the intervention, there was an increase in the volume of the three targeted antitumor drugs. After policy intervention, there was a decrease in both the volume and expenditures of original drugs. The volume of afatinib (30 mg), afatinib (40 mg), and sunitinib postintervention exhibited a significant increase of 305.26%, 167.31%, and 347.94%, respectively. Conversely, the employment of three original drugs witnessed a notable decrease of 85.79%, 43.45%, and 91.32% along with a corresponding expenditure reduction of 81.64%, 43.45%, and 93.10%.

3.2. The Results of ITS Analysis

Table 3 shows the results of the stepwise regression analysis of the volume, expenditures, and DDDc of the three targeted antitumor drugs. The volume of generic afatinib (30 mg) increased by 25.78 DDDs, the expenditures decreased by 3641.14 yuan (95% CI: −5581.16 to −1701.12, p = 0.001), and the DDDc decreased by 124.35 yuan (95% CI: −128.23 to −120.46, p < 0.001). The volume of generic afatinib (40 mg) increased by 65.19 DDDs (95% CI: 35.38 to 96.43, p < 0.001), the expenditures increased by 1304.93 yuan (95% CI: 700.55 to 1909.31, p < 0.001), and the DDDc decreased by 120.2 yuan (95% CI: −120.2 to −120.2, p < 0.001). The volume of generic sunitinib increased by 75.79DDDs (95% CI: 37.99 to 112.46, p < 0.001), the expenditures decreased by 15869.78 yuan (95% CI: −23275.57 to −8463.98, p < 0.001), and the DDDc decreased by 243.28 yuan. There was no significant change trend in volume, expenditures, and DDDc of the three original-targeted drugs after NCDP intervention.

4.1. Drug Utilization

In this study, our findings indicate a significant increase in the use of generic-targeted antitumor drugs following policy implementation (305.26%, 167.31%, and 347.94%), which is consistent with previous studies. Lu et al. [20] reported a 405.31% increase in the consumption of standardized drugs (β = 1.62, p < 0.001). Zhu et al. [21] demonstrated that policy interventions enhanced accessibility and reduced costs for certain cancer drugs in China. At the same time, the expenditure of the generic-targeted antitumor drugs decreased (−81.64%, −43.45%, and −93.10%), and the DDDc decreased (−85.54%, −85.86%, and −84.93%), which met the requirements of the NCDP to reduce medicines’ cost and alleviate the drug burden of patients, which was similar to the results of previous studies [22, 23]. Furthermore, a significant decrease in both the quantity and dosage of original-targeted drugs employed was observed subsequent to the policy intervention, aligning with those reported in previous studies [7, 10–12].

4.2. ITS Analysis of Changes in Volume, Expenditures, and DDDc

This study employed an intermittent time-series analysis of 18-month data on the clinical utilization of three targeted antitumor drugs to investigate the impact of the seventh round of NCDP on drug quantity, expenditures, and daily costs associated with these medications. The interrupted time-series analysis revealed a significant increase in the volume and expenditure of generic afatinib (40 mg) following the policy intervention, accompanied by a notable decrease in cost. The results of the study are similar to some previous research. Yang et al. demonstrated that following the implementation of the “4 + 7” policy, there was a significant increase in the utilization of generic antihypertensive medications (3.12 million DDD, 95% CI = 2.14–4.10, p < 0.001), and a substantial reduction in DDDc (−1.30 CNY, 95% CI = −1.43–1.18, p < 0.001) [7]. Wen et al. observed a significant increase in the utilization of generic serotonin-specific reuptake inhibitors (SSRIs) following the implementation of the “4 + 7” policy (β = −224.17, p < 0.001) [10]. Yang et al. also reported a 436.31 thousand increase in the total DDDs of generic antibiotics after the implementation of the “4 + 7” policy (p = 0.001) [11]. The generic afatinib (30 mg) does not satisfy the criteria outlined in the NCDP policy for enhancing utilization, reducing costs, and mitigating patient burden, thereby conflicting with the conclusions drawn from several prior studies [7, 10–12, 22]. It is possible that clinicians may have a preference for the clinical use of afatinib (40 mg), while the higher price of afatinib (30 mg) in our institution could also be a contributing factor to its nonselection. Further exploration of these factors is warranted. Afatinib (30 mg) exhibiths limited substitutability and fails to yield desired policy outcomes. Simultaneously, we observed a significant downward trend in both volume and expenditures of original afatinib (30 mg and 40 mg) before policy intervention. The potential correlation may stem from the clinical efficacy of afatinib itself, given its classification as a second-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) with a higher incidence of adverse reactions and significantly increased toxicity [24]. Consequently, healthcare professionals might opt for alternative EGFR-TKI in their treatment approach.

Our study revealed that the generic sunitinib complied with the NCDP, enhancing its utilization and reducing medical consumption (volume = 75.79, p < 0.001; expenditure = −15869.78, p < 0.001; DDDc = −243.28, p < 0.001). The findings are consistent with prior research indicating an increase in the utilization of generic drugs and a decrease in costs following policy interventions [7, 10–12]. The use and amount of original drugs showed a downward trend, although there was no statistical significance. Clinical studies have demonstrated that sunitinib has a considerably high occurrence rate of adverse reactions [25], while its optimal dosage and treatment cycle remain controversial [26, 27]. Furthermore, the dosages recommended of sunitinib by international guidelines for Asian populations were lacking [28–30]. The side-effect profile of the original and generic sunitinib has not been shown to differ clinically. The substantial expenses linked to the original pharmaceutical may prompt healthcare professionals to favor cost-effective alternatives that guarantee consistent treatment. To facilitate the comprehensive evaluation of sunitinib’s clinical utility, it was recommended that the manufacturer undertake additional patient-oriented clinical trials to optimize drug efficacy, mitigate adverse reactions, and provide patients with cost-effective and high-quality treatment.

Consistency in drug quality does not necessarily equate to consistency in real-world clinical efficacy. While price is an important consideration in our centralized procurement process, however, it is unclear whether the lowest price for a drug will always be the best value [31]. The implementation of the national centralized procurement policy has been shown in related studies to successfully promote the substitution of generic drugs for original drugs, particularly in the case of antihypertensive drugs, antidepressants, and antibiotics. However, the results of this study suggest that there may be some specificity in targeted anticancer drugs, as price is not the only factor affecting the use, and the clinical efficacy and safety of the drug may also affect the use of targeted anticancer drugs. To optimize the clinical efficacy and safety of generic drugs, the following strategies can be implemented: (1) pharmaceutical manufacturers should enhance their pharmaceutical standards and intensify authentic drug research and clinical practice and (2) evaluate whether specific gene-related drugs, such as targeted antitumor medications in our investigation, are suitable for particular ethnic groups and necessitate revalidation through rigorous clinical trials. (3) Healthcare institutions should expeditiously report adverse drug reactions to facilitate manufacturers in investigating causality and refining generic drugs accordingly. (4) Patients should provide timely feedback on medication usage and maintain open dialogue with healthcare professionals.

There are several potential limitations associated with this study. First, our data were obtained from three hospitals, thus the involvement of too few public medical institutions may limit the generalizability of our findings. We hope that future studies can supplement additional clinical usage data from a wider range of healthcare facilities. Second, due to considerations regarding the timing of policy intervention and baseline data stability, this study only encompasses 18 months’ worth of data with a postintervention period spanning merely 7 months; therefore, there may be certain limitations when exploring long-term trends related to the impact of this policy.