Five-year survival of patients with non-small cell lung cancer treated with alkalization therapy.

Introduction
Lung cancer remains the leading cause of cancer-related mortality worldwide, with non-small cell lung cancer (NSCLC) accounting for approximately 85 % of all cases [1]. Despite recent advances in various cancer treatments, the prognosis of advanced NSCLC remains poor, with the 5-year survival rate for stage IV disease being only 6·4 % in Japan [2].
The metabolism of cancer cells deviates from typical metabolic regulation, which then promotes aerobic glycolysis, known as the Warburg effect [3,4]. The activation of this “glycolytic switch” is a crucial factor that promotes tumorigenesis and is observed in approximately 70 % to 80 % of human cancers [5]. This metabolic reprogramming promotes the acidic tumor microenvironment (TME). The excess protons generated by aerobic glycolysis are expelled from cancer cells by pumps such as sodium-hydrogen exchanger isoform 1, creating a highly acidic microenvironment around the cancer cells [[6], [7.], [8]].
The acidified TME substantially affects tumor progression and promotes a wide range of malignant phenotypes, including increased malignancy; enhanced activation of cell proliferation and division cycles; expression and activation of genetic abnormalities and oncogenes; stimulation of cell proliferation factors; elevated glycolytic activity; activation of DNA synthesis; promotion of cell migration; induction of angiogenesis; increased metastatic potential; and activation of multidrug resistance genes [[9], [10], [11], [12], [13]]. Moreover, a strong association between increased intracellular pH (pHi) and the acquisition of multidrug resistance has been established [7]. In human lung cancer cells, an increase in pHi from 7·0 to 7·4 enhances resistance to adriamycin by approximately 2000-fold [14].
These findings suggest that modulating acidification in cancer cells and the surrounding microenvironment may be relevant for developing more effective treatment strategies. The concept of “alkalization therapy” is a supportive, pragmatic approach intended to reduce systemic proton excretion and potentially modulate the acidified TME. Alkalization therapy focuses on minimizing the intake of meat and processed foods to reduce the acid load and support a systemic alkaline environment [15]. Additionally, oral administration of sodium bicarbonate and citric acid, combined with dietary modifications, aims to modulate systemic proton excretion [16]. In our recent report, the 5-year survival rate of patients with stage IV NSCLC, pancreatic cancer, and breast cancer who underwent alkalization therapy demonstrated favorable outcomes [17], although these observational findings do not establish causality and may be influenced by patient selection, adherence, or other unmeasured factors. Accordingly, alkalization therapy has been proposed as a potential adjunctive strategy, and its clinical relevance warrants further evaluation.
Concerning the long-term prognosis of NSCLC, particularly in relation to molecular subtypes, such as EGFR mutation status, definitive conclusions remain unavailable. Therefore, this study examined the 5-year survival outcomes of patients with stage IV NSCLC who underwent alkalization therapy at the Karasuma Wada Clinic, with additional analyses segmented by EGFR mutation status. Given the retrospective single-center design and the absence of an internal control group, the present analyses were intended to describe associations rather than infer therapeutic effects.

Methods

Study design
This retrospective study aimed to evaluate the 5-year survival rates and long-term effects of alkalization therapy in patients with stage IV NSCLC. A total of 203 patients who first visited the Karasuma Wada Clinic between January 2014 and December 2019 were included in this study (Fig. 1). Patients were followed from their initial visit until 7 January 2025. For each patient, the mean urinary pH during the follow-up period was calculated, excluding the value at the first visit. Patients who visited the clinic at least three times and provided urine samples at each visit were included in this study. Data were obtained from the clinic’s medical records.
Among the study cohort, 103 patients were positive for EGFR or ALK mutations, and 100 patients were negative. Additionally, stage IV recurrence was observed in 26 patients with EGFR/ALK mutation-negative disease and 34 patients with EGFR/ALK mutation-positive disease following surgery. Patients with EGFR or ALK mutations received tyrosine kinase inhibitors (TKIs), including gefitinib, osimertinib, alectinib, crizotinib, ceritinib, erlotinib, and afatinib.
All patients received alkalization therapy, which included an alkalizing diet and oral intake of alkalizing agents, such as sodium bicarbonate and citric acid. The patients attended at least three outpatient visits and followed the alkalization therapy protocol outlined below. During each visit, the patients received instructions regarding the details of the alkalization therapy.
The study was conducted in accordance with the Declaration of Helsinki, approved by the Institutional Review Board of the Japan Chapter of the American College of Chest Physicians (approval number 2023–1), and registered with the UMIN Clinical Trials under registration number UMIN000052333 (date of registration, 21 September 2023). Written informed consent for study participation and for publication of anonymized data was obtained from all participants prior to enrollment.

Alkalization therapy
During alkalization therapy, patients were instructed to follow a diet with a low potential renal acid load (PRAL) [[18], [19], [20], [21]]. They were advised to consume at least 300 g of vegetables per day, avoid beef and pork, and use fish or chicken as alternative sources of animal protein. If a patient’s urine pH increased to ≥7·5 with dietary intervention alone, alkalization therapy was continued with diet only. If this target was not achieved, oral alkalizing agents were added, consisting of potassium/sodium citrate (3–4·5 g/day as citrate) and/or sodium bicarbonate 3–6 g/day [22,23].

Statistical analysis
Survival functions were estimated using the Kaplan–Meier method, and differences among pH-level groups were evaluated with the log-rank and Gehan–Breslow–Wilcoxon tests. All statistical analyses were performed using JMP Pro for Windows, version 13.0 (SAS Institute Inc., Cary, NC, USA). Statistical significance was defined as a two-sided alpha level of 0.05.

Results
Among patients with stage IV NSCLC, the mean age was 67·1 ± 11·4 years in the EGFR/ALK mutation-negative group and 62·3 ± 12·3 years in the EGFR/ALK mutation-positive group (Table 1). The corresponding mean urine pH values were 6·95±0·82 and 7·28±0·64, respectively. The mutation-negative group included 68 men (68·0 %), whereas the mutation-positive group included 27 men (26·2 %). Postoperative recurrence was observed in 26 patients (26·0 %) in the mutation-negative group and 34 patients (33·0 %) in the mutation-positive group. Patients with EGFR or ALK mutations received one or more TKIs, most commonly gefitinib (55 %) and osimertinib (37 %), followed by alectinib (10 %), crizotinib (3 %), ceritinib (2 %), erlotinib (8 %), and afatinib (4 %).The 5-year survival rate among patients with stage IV NSCLC in our cohort was 49·0 % (95 % confidence interval [CI] 38·3–59·8) (Fig. 2), compared with a nationwide average of 6·4 % reported by the National Cancer Center of Japan2. The 5-year survival rates were 49·9 % (95 % CI 35·5–64·2) in patients with EGFR/ALK mutation-positive disease and 48·6 % (95 % CI 33·8–63·7) in those with mutation-negative disease. Although no significant difference was observed with the log-rank test (p = 0·16; Fig. 3), the Gehan–Breslow–Wilcoxon test demonstrated a statistically significant difference between the two groups (p = 0·01), indicating that any survival advantage associated with EGFR/ALK mutation positivity was more pronounced in the early phase of treatment. These results suggest that the initial therapeutic effects of TKIs are most evident in mutation-positive patients shortly after treatment initiation. In contrast, the convergence of the survival curves in the mid-to-late phases, together with the favorable long-term outcomes observed in both groups, raises the possibility that concomitant alkalization therapy may have contributed to maintaining long-term disease control irrespective of mutation status.

EGFR/ALK-negative
Among patients with EGFR/ALK-negative stage IV NSCLC, the 5-year survival rate was 65·5 % (95 % CI 35·1–86·9) in those who developed postoperative recurrence, compared with 42·0 % (95 % CI 25·6–60·4) in patients presenting with de novo stage IV (metastatic) disease, with a statistically significant difference on the log-rank test (p = 0·02; Fig. 4A). The association between mean urine pH and survival was then evaluated. The 5-year survival rate was 39·3 % in the 68 patients with urine pH <7·5 and 70·0 % in the 32 patients with urine pH ≥7·5, with the log-rank test demonstrating a statistically significant difference between the two groups (p = 0·01; Fig. 4B). In a Cox proportional hazards regression model incorporating the dates of stage IV diagnosis and initiation of alkalization therapy at our institution as time-dependent covariates, higher urine pH was associated with a trend toward improved survival, and postoperative recurrence was likewise associated with more favorable survival (Supplementary Data 1).

EGFR/ALK-positive
Among patients with EGFR/ALK-positive stage IV NSCLC, the 5-year survival rate was 62·3 % (95 % CI 37·2–82·2) in those who developed postoperative recurrence, compared with 43·0 % (95 % CI 26·8–61·1) in patients presenting with de novo stage IV (metastatic) disease. Although this difference did not reach conventional statistical significance, the postoperative recurrence group tended to have better survival than the de novo metastatic group, with p = 0·21 for the log-rank test and p = 0·12 for the Wilcoxon test (Fig. 5).

Discussion
In this study, the 5-year survival rate among patients with stage IV NSCLC was 49·0 %. The 5-year survival rates were 49·9 % in patients with EGFR/ALK-positive disease and 48·6 % in those with EGFR/ALK-negative disease, with p = 0·21 for the log-rank test and p = 0·12 for the Wilcoxon test. Although neither comparison reached conventional statistical significance, the relatively smaller p-value for the Wilcoxon test is informative regarding the pattern of treatment effect over time. In general, the log-rank test is most sensitive to differences in survival over the entire follow-up period, whereas the Wilcoxon test places greater weight on early events. The relatively small p-value for the Wilcoxon test suggests that early survival differences between subgroups may be present, whereas this early advantage appears to attenuate over time, resulting in no clear long-term difference in the log-rank comparison; however, this interpretation is exploratory and should be viewed cautiously, particularly given potential time-dependent confounding and the non-randomized nature of treatments. Taken together with the favorable survival observed in both molecular subgroups, these findings raise the hypothesis that factors associated with the pragmatic alkalization strategy—implemented concomitantly with standard anticancer therapies—may be linked to longer-term outcomes and to smaller apparent survival differences by EGFR/ALK mutation status in this cohort. Importantly, because all patients received alkalization-oriented management and no internal control group is available, the observed outcomes cannot be attributed to alkalization therapy. The results may instead reflect selection or referral patterns, patient motivation, adherence to anticancer therapy and supportive care, or other unmeasured prognostic factors. To explore whether urinary pH is associated with outcomes among patients with EGFR/ALK-negative NSCLC, we stratified patients with EGFR/ALK-negative NSCLC using a urine pH cutoff of 7·5 and compared survival outcomes. Patients in the higher urinary pH group had a more favorable prognosis. With alkalizing interventions, urinary pH may trend toward less acidity and may indirectly suggest a reduced systemic acid load. However, urinary pH is a multifactorial, indirect measure and does not directly quantify net acid excretion. Moreover, urinary pH may function as a surrogate marker of broader health behaviors and engagement with treatment (e.g., adherence to alkalizing agents and dietary guidance, and the frequency of self-monitoring) rather than a direct biological mediator of tumor control. Accordingly, in this study, urinary pH should be interpreted as an observational indicator associated with outcomes.
We have previously reported an association between higher urine pH and improved survival in patients receiving alkalization therapy [17]. The rationale for this therapeutic approach is to correct tumor microenvironment (TME) acidification by combining a diet characterized by low PRAL with alkalizing agents such as sodium bicarbonate and citrate. Preclinical studies are consistent with this concept, including reports of enhanced antitumor activity of S-1 plus sodium bicarbonate in pancreatic cancer models and improved doxorubicin efficacy through TME neutralization with oral sodium bicarbonate in colon cancer models [24]. The association observed in the present study between higher urine pH and a more favorable prognosis is broadly aligned with these experimental data; however, whether urinary alkalization causally modifies the TME or improves clinical outcomes cannot be determined from the current observational design.Among patients with EGFR/ALK-positive stage IV NSCLC in our cohort, the 5-year survival rate was 50·0 %. Previous studies have reported 5-year survival rates ranging from 14·6 % to 44 % in this population [[25], [26], [27], [28]], suggesting that outcomes in our cohort were relatively favorable. However, comparisons across studies should be made cautiously given differences in patient selection, treatment era, and available systemic therapies. Interpreting urine pH as a prognostic marker in this subgroup is complicated by substantial heterogeneity in TKI duration and sequencing. Prospective studies are warranted to more precisely characterize the relationship between urine pH and prognosis in EGFR/ALK-positive NSCLC.
This study has several limitations. First, this single-center retrospective analysis included no internal control group, and therefore precludes causal inference regarding any therapeutic effect of alkalization. Second, we did not adequately control for the impact of immunotherapy and other systemic treatments on clinical outcomes. Because treatment regimens and sequencing evolved over the inclusion period, residual confounding is likely. Third, although information on prior treatments at other institutions was available at the initial consultation, only partial data on treatments administered after the first visit outside the Wada Clinic were collected. Regular and thorough follow-up of these variables may be essential to more accurately assess treatment outcomes. Finally, while the findings are promising, the single-institution, non-randomized study design naturally limits external validity. Future validation through randomized controlled trials or well-structured matched cohort studies is necessary to confirm these findings.

Conclusion
While survival outcomes in patients with EGFR/ALK-positive NSCLC should be interpreted with caution, this study provides novel insights, particularly in the EGFR/ALK-negative subgroup, in which higher urinary pH was associated with a more favorable prognosis. However, urinary pH may reflect adherence to dietary/supportive recommendations or other health behaviors, and the present data do not establish a causal relationship between alkalization therapy and survival. Alkalization therapy, combining a low-PRAL diet with supplementation using sodium bicarbonate and citrate, warrants further evaluation as a potential adjunct to standard systemic therapy in prospective controlled studies, rather than being interpreted as conferring a direct survival benefit. In this study, the association of alkalization-oriented management and urinary pH with outcomes in stage IV NSCLC was evaluated observationally. These findings are consistent with the concept of metabolic reprogramming in cancer treatment and suggest that metabolic and microenvironmental factors, along with treatment adherence and supportive care practices, may contribute to the development of more targeted and effective therapeutic strategies for patients with advanced NSCLC.
Baseline demographic and clinical characteristics of 203 patients with stage IV non-small cell lung cancer (NSCLC) treated with alkalization therapy, stratified by EGFR/ALK mutation status (100 EGFR/ALK mutation-negative and 103 mutation-positive patients). Data are presented as mean ± standard deviation or n ( %).

Funding information
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data sharing
No additional data are available. Data sharing is not applicable as no new datasets were generated or analyzed in this study.

CRediT authorship contribution statement
Shion Kachi: Writing – review & editing, Writing – original draft, Investigation, Formal analysis, Data curation, Conceptualization. Kazuyuki Suzuki: Writing – review & editing, Investigation, Formal analysis, Data curation, Conceptualization. Reo Hamaguchi: Writing – review & editing, Supervision, Data curation, Conceptualization. Ryoko Narui: Writing – review & editing, Conceptualization. Hiromasa Morikawa: Writing – review & editing, Investigation, Data curation. Hiromi Wada: Writing – review & editing, Supervision, Project administration, Investigation, Data curation.

Declaration of competing interest
The authors declare no competing interests.