抗膀胱癌新型制剂——重组卡介苗的研究

卡介苗(BCG)不仅是一种活疫苗,而且还是外源基因的表达载体和较强的免疫佐剂。基因重组卡介苗(rBCG)是借助分子生物学技术,将外源基因导入BCG中构建而成的多价疫苗。rBCG可诱导长期的体液免疫和细胞免疫,初步的研究结果已显示出rBCG具有广阔的应用前景,有望发展成为一种经济有效的新型疫苗,以预防传染病和一些肿瘤。本文结合作者最近的研究,就rBCG的构建、表达、特点、应用、存在的问题及应用前景等作一阐述。     

Safety and immunoresponse study of intravesical instillation of Taipei-NIPM bacillus Calmette-Guérin.

The intravesical instillation of bacillus Calmette-Guérin (BCG) has proved to be an effective modality for prophylaxis of recurrent superficial bladder cancer and treatment of carcinoma in situ. The domestic BCG, named Taipei-NIPM, which is produced by the National Institute of Preventive Medicine, has been used as an anti-TBC vaccine in Taiwan for decades. In this study, we have investigated the safety and immune response in animals after intravesical BCG treatment to test its feasibility in future clinical application. Weekly instillation of BCG (1 mg/ml, 5-8 x 10(7) CFU/mg) for 6 instillations could induce lymphocytic infiltration, submucosal fibrosis, and granulomatous reaction after 4 weeks with mild decrease of bladder weight and high incidence of hematopyuria (75%). No changes in appetite, body weight, and splenic weight were noticed in the chronically treated rats. A delayed hypersensitivity test through foot pad swelling measurement reached 80% positive rates at 2 weeks. Cystometric study revealed a mild decrease in bladder capacity (33.3%) at 2 weeks and of contractile pressure of the urinary bladder in rats receiving BCG instillations. In addition, increase in lymphocytic infiltration by natural killer (NK) cells against YAC-1 cells could be detected after BCG treatment and this was related to dosage of BCG. The urothelial damage by cauterization and the number of instillations could also enhance NK cell activity. Low toxicity and high safety of intravesical instillation of the domestic BCG are demonstrated by this pilot animal study. This information on local and systemic immune responses can provide a solid base for future efficacy of BCG immunotherapy in bladder cancer patients using this domestic strain BCG.     

Intravesical Bacille Calmette-Guérin Eradicates Bacteriuria in Antibiotic-naïve Bladder Cancer Patients

Background

Intravesical bacille Calmette-Guérin (BCG) therapy is safe and effective in bladder cancer patients who have asymptomatic bacteriuria. BCG induces robust immune responses in the bladder that are responsible for its antitumor effect. We hypothesize that BCG-induced inflammation may eradicate bacterial infection.

Objective

To investigate whether intravesical BCG therapy alone can eradicate bacterial infection in antibiotic-naïve bladder tumor patients who have asymptomatic bacteriuria.

Design, setting, and participants

A single-institution prospective cohort study of bacteriuric adults with non–muscle-invasive bladder tumors who underwent outpatient BCG therapy or surveillance cystoscopy.

Intervention

Ninety high-risk patients received induction intravesical BCG without maintenance BCG, and 95 low-risk patients who had not received BCG underwent outpatient surveillance cystoscopy. Each patient had significant bacteriuria on urine culture, and none received routine antibiotics before, during, or after procedures.

Outcome measurements and statistical analysis

Urine cultures were repeated after 3, 6, and 12 mo. All patients had follow-up cystoscopy every 3 mo and were followed for a minimum of 1 yr. The end point was number of BCG-treated and cystoscopy patients who became bacteria free at 3, 6, and 12 mo.

Results and limitations

Two BCG-treated patients (2.2%) and six patients after cystoscopy (6%) developed febrile urinary tract infection (p = 0.21). All resolved with antibiotics. No patient was admitted for sepsis. Of 88 infected patients who received BCG without routine antibiotics, 58 (66%) were continuously bacteria free at 1 yr compared with 16 of 89 cystoscopy patients (18%; p = 0.001). The prospective observational study design prohibits causal inference of antibacterial effects attributed to BCG over cystoscopy.

Conclusions

Intravesical BCG therapy is associated with clearance of uropathogens in bladder cancer patients, possibly due to augmented innate host immunity.     

Immunotherapy of murine bladder cancer by irradiated tumor vaccine

This investigation explored the efficacy of irradiated autologous mouse bladder tumor (Ir-MBT2) as an active specific immunotherapeutic agent and as adjuvant therapy with Bacillus Calmette-Guerin (BCG) against a subcutaneously transplanted murine bladder tumor. Tumor incidence was significantly reduced in groups receiving BCG (27%, p less than 0.005) or Ir-MBT2 with BCG (53%, p less than 0.025), compared to control (93%). Survival was significantly improved in groups treated with BCG (100%, p less than 0.005), 10(5) Ir-MBT2 with BCG (53%, p less than 0.01), or 10(7) Ir-MBT2 with BCG (47%, p less than 0.025) compared with control (13%). Surprisingly, Ir-MBT2 consistently reduced the efficacy of BCG alone. Ir-MBT2 alone (10(7)) appeared to enhance tumor growth. Autologous irradiated bladder tumor vaccine, alone or in combination with BCG, displayed no immunotherapeutic advantage. The use of irradiated tumor cell vaccine for bladder cancer therapy may reduce the results achievable with BCG alone.     

Immune mechanisms in bacillus Calmette-Guerin immunotherapy for superficial bladder cancer

PURPOSE: Of all medical disciplines it is exclusively in urology in which immunotherapy for cancer has an established position today with intravesical bacillus Calmette-Guerin (BCG) against superficial bladder carcinoma recurrences. BCG is regarded as the most successful immunotherapy to date. However, the mode of action has not yet been fully elucidated. We provide a thorough overview of this complex field of research. MATERIALS AND METHODS: Rather than simply reporting all experimental data available for better understanding the involved immune mechanisms, we chose to provide comprehensively only information supported by several independent pathways of evidence. RESULTS: Major findings made during the last few years include systematic analyses of patient material, detailed in vitro studies and investigations in animal models, which have led to a substantially greater understanding of the mechanisms involved. CONCLUSIONS: The efficacy of BCG is based on a complex and long lasting local immune activation. The bladder as a confined compartment, in which high local concentrations of the immunotherapy agent and effective recruitment of immune cells can be achieved, serves as an ideal target organ for this type of immunotherapy approach.     

Immunotheapy and immunodiagnostic studies in carcinoma of the bladder

Summary Non-specific immunotherapy of superficial bladder cancer using Bacillus Calmette-Guérin (BCG) represents a successful application of immunotherapy against a human cancer. Clinical studies in the late 1970's first demonstrated the efficacy of this form of therapy against papillary forms of transitional cell carcinoma. Subsequent studies confirmed the value of BCG in extending the time to recurrence and decreasing both the rate of recurrence and the rate of progression of recurrent tumor to higher stages. These studies also showed BCG to be effective against carcinoma in situ. However, the mechanism of action of BCG has not yet been defined, nor has the optimal dosage schedule and route of administration been determined. Preliminary laboratory studies of tumor-specific therapy with tumor-derived protein extracts are encouraging, and suggest that this form of immunotherapy may be almost as efficacious as BCG therapy. Clinical trials of intravesical alpha-2 interferon for carcinoma in-situ are also in progress.     

Immunotherapy for superficial bladder cancer. A developmental and clinical overview.

Superficial bladder cancer is one of the few solid human malignancies in which immunotherapy has been proved to be effective. Bacillus Calmette-Guérin was the vaccine which opened the door for this innovative approach. In an era of remarkable achievements in biotechnology, it is truly amazing that this throwback to the Stone Age of tumor immunology has not yet been replaced by a more (or equally) effective substitute. Potential candidates are already on the horizon and deserve a comprehensive evaluation. They must show not only that they are devoid of significant adverse effects but that they possess, beyond a doubt, superior antineoplastic activity. Even more remarkable is that one of the oldest vaccines still in use could emerge in a new role as an effective antineoplastic agent. Bacillus Calmette-Guérin has demonstrated an uncanny capacity for effectiveness as therapy for human diseases. Its protective effect against tuberculosis is well recognized, and its contribution to cancer therapy is widely known. A new and increasing repertoire has recently been presented: two separate groups of researchers have employed the vaccine successfully as a vehicle to express antigen-encoded genes from other pathogens. The exciting aspect of these recent studies resides in the demonstration that the altered vaccine is able to induce humoral and cell-mediated immune responses to the recombinant antigens, including the human immunodeficiency virus (HIV). Thus, BCG once more attracts enormous interest from the scientific community for its versatility and potential as a therapeutic agent.     

Role of immunotherapy in the prevention of recurrence and invasion of urothelial bladder tumors: a review

Summary Although many different chemotherapeutic regimens for the treatment of superficial bladder cancer have been used, none are considered ideal. This has stimulated investigations of alternative forms of therapy, including immunotherapy. Contained within this therapeutic category are bacterial agents such as Bacille Calmette-Guerin, Corynebacterium parvum and a streptococcal preparation, OK-432, as well as the interferon inducer polyriboinosinic acid-polyribocytidylic and passive immunotherapy with sensitized pig lymphocytes. With the exception of BCG, most forms of immunotherapy have not been been effective in the treatment of superficial bladder carcinoma. This paper reviews immunotherapy with emphasis on the studies of BCG as prophylaxis against and treatment for superficial transitional cell carcinoma of the bladder.Supported in part by USPHS Grant CA 09118     

Recombinant BCG therapy suppresses melanoma tumor growth

Background: Melanoma is the fastest rising cancer in the United States. Bacillus Calmette-Guerin (BCG) has been genetically engineered to actively express and secrete the cytokine interleukin-2 (IL-2). Both BCG and IL-2 have known potent antitumor and immunomodulatory properties. Methods: This recombinant BCG (rBCG 3A) has been tested as an intratumoral injection and a vaccine therapy in conjunction with irradiated tumor cells against melanoma in the murine B16 melanoma model. Results: The transfection process did not adversely after the function of the wild-type (WT) BCG. rBCG 3A and WT BCG are equally effective intratumoral and vaccine therapies against melanoma when compared with normal saline control groups. Tumor burdens were significantly smaller (p</0.01 and 0.05) for the treatment groups for both intratumoral and vaccine administration of therapy. Immunization with rBCG 3A and WT BCG 14 days before a B16 challenge resulted in an ∼45% smaller tumor burden when compared with controls. Conclusions: Novel therapies based on the immunogenic properties of melanoma combined with molecular technologies may offer promise for an effective and safe treatment of melanoma. Results of this study were presented at the 47th Annual Cancer Symposium of The Society of Surgical Oncology, Houston, Texas, March 20, 1994.     

Tumor-specific immunotherapy of murine bladder cancer with butanol-extracted antigens and ethylchlorformate polymerized tumor protein

Successful treatment of superficial bladder cancer using nonspecific immunotherapy with Bacillus Calmette-Guerin (BCG) has been well documented. Investigation of two potential tumor-specific immunotherapeutic agents using a murine transitional-cell carcinoma model (MBT-2) is reported. The survival of mice immunized with tumor proteins obtained by treating tumor cells with either 1-butanol or ethylchlorformate was compared to the survival of animals immunized with BCG. Long-term immunity conferred by each of these agents was also assessed. Significant protection by both agents was noted in all treatment groups compared to controls. Long-term immunity was also found to result from treatment with both investigational agents as well as with BCG. Butanol-extracted antigens and ethylchlorformate polymerized tumor protein may be useful as immunotherapeutic alternatives to BCG.     

The therapeutic potential of recombinant BCG expressing the antigen S1PT in the intravesical treatment of bladder cancer

PurposeBacillus Calmette-Guerin (BCG) continues to be employed as the most effective immunotherapy against superficial bladder cancer. We have developed an rBCG-S1PT strain that induces a stronger cellular immune response than BCG. This preclinical study was designed to test the potential of rBCG-S1PT as an immunotherapeutic agent for intravesical bladder cancer therapy.Materials and methodsA tumor was induced in C57BL/6 mice after chemical cauterization of the bladder and inoculation of the tumor cell line MB49. Next, mice were treated by intravesical instillation with BCG, rBCG-S1PT, or PBS once a week for 4 weeks. After 35 days, the bladders were removed and weighed, Th1 (IL-2, IL-12, INOS, INF-γ, TNF-α), and Th2 (IL-5, IL-6, IL-10, TGF-β) cytokine mRNA responses in individual mice bladders were measured by quantitative real time PCR, and the viability of MB49 cells in 18-hour coculture with splenocytes from treated mice was assessed. In an equivalent experiment, animals were observed for 60 days to quantify their survival.ResultsBoth BCG and rBCG-S1PT immunotherapy resulted in bladder weight reduction, and rBCG-S1PT increased survival time compared with the control group. There were increases in TNF-α in the BCG treated group, as well as increases in TNF-α and IL-10 mRNA in the rBCG-S1PT group. The viability of MB49 cells cocultured with splenocytes from rBCG-S1PT-treated mice was lower than in both the BCG and control groups.ConclusionsrBCG-S1PT therapy improved outcomes and lengthened survival times. These results indicate that rBCG could serve as a useful substitute for wild-type BCG.     

Do prognostic parameters of remission versus relapse after Bacillus Calmette-Guérin (BCG) immunotherapy exist?. analysis of a quarter century of literature

OBJECTIVE: To review prognostic factors identified in clinical trials for remission versus relapse after intravesical adjuvant Bacillus Calmette-Guérin (BCG) immunotherapy for superficial bladder cancer (Ta, T1, and carcinoma in situ). MATERIALS AND METHODS: Information was retrieved by a MEDLINE search of the English literature. Indexing terms comprised bladder cancer, bladder neoplasm, BCG vaccine, superficial bladder cancer, immunotherapy, intravesical therapy, prognostic marker, and Bacillus Calmette-Guérin. Fifty clinical studies were assessed for the strength of their results on the therapeutic response to BCG instillation. Emphasis was placed on clinical trials that assessed tumor and/or host characteristics, immunological reactions, recurrence rates, progression rates and disease-specific survival after BCG. RESULTS: The predictive value of host factors is extremely controversial, but marked adverse reactions to BCG instillation appear to be associated with a better tumor response. Traditional pathological tumor characteristics, molecular markers (p53) and immunological status (PPD skin test) do not appear to have prognostic value in this setting. There is increasing evidence that immunologic markers are predictive of the BCG response, but most of them have not yet been assessed in large prospective studies. Histologic/cytologic response criteria are the critical determinant of post-BCG outcome. CONCLUSIONS: After a quarter century of clinical research, no independent prognostic factor for the bladder tumor response to BCG has yet been identified. Sophisticated individual therapeutic approaches (SITA) appear to be the most promising. Nomograms based on host, tumor and immunological characteristics may help with clinical decision-making and with rationalized BCG schedule design.     

Expression of RPL9 predicts the recurrence of non-muscle invasive bladder cancer with BCG therapy

Numerous biomarkers and risk tables can be used to predict recurrence or progression of patients with primary or recurrent non-muscle invasive bladder cancer (NMIBC) receiving Bacillus Calmette-Guerin (BCG). However, few are suitable for BCG-unresponsive disease (i.e., recurrence or progression after BCG treatment). Therefore, identification of a novel marker that allows accurate prediction of prognosis, particularly risk of recurrence, is critically important in clinical practice. In the current study, gene ontology and gene set enrichment analyses of microarray datasets (GSE13507, n = 47) revealed that differentially expressed genes in recurred NMIBC patients after BCG treatment were associated with virus and ribosomal pathways. Among the core-enrichment genes, the expression of RPL9, a putative tumor suppressor, was lower in recurred NMIBC patients after BCG therapy than in patients without recurrence (P = 0.033) from the E-MTAT-4321 European cohort (n = 84). Data from The Cancer Genome Atlas (n = 406) showed that bladder cancer patients with higher RPL9 expression had a longer overall survival probability than patients with lower RPL9 expression (P = 0.011). Moreover, we used the latest digital PCR platform to examine 59 NMIBC patients and identified downregulation of RPL9 in patients with recurrence after BCG therapy (P = 0.031). The Kaplan–Meier survival estimator showed that NMIBC patients with higher expression of RPL9 had longer recurrence-free survival (log-rank test, P = 0.015). Therefore, we conclude that RPL9 expression is a prospective predictor of recurrence after BCG therapy in NMIBC patients.     

Immune checkpoints inhibitors in the management of high-risk non-muscle-invasive bladder cancer. A scoping review

PurposeProvide the current state of trials investigating the effectiveness and safety of checkpoint inhibitors in patients with non-muscle invasive bladder cancer.MethodsWe conducted this scoping review following the recommendations of the Joanna Briggs Institute. We searched for MEDLINE, EMBASE, CENTRAL databases, and clinical trials in search engines such as clinicaltrials.gov and clinicaltrialsregister.eu. We included clinical trials in patients over 18 years of age diagnosed with high-risk non-muscle-invasive bladder cancer who suffer treatment failure with Bacillus Calmette-Guérin (BCG). Even those who have not received prior therapy. Those clinical trials also evaluated intravenous- or intravesical-administered immune checkpoint inhibitors and those associated with BCG.ResultsThirteen clinical trials are currently being developed with immune checkpoint inhibitors as a therapeutic alternative in patients diagnosed with non-muscle-invasive urothelial carcinoma of the bladder. Five of these have not received prior therapy with bacillus Calmette-Guérin. The remaining eight studies in patients who received BCG immunotherapy with a poor response are classified as persistent, refractory, or non-responders to BCG therapy. Also, in patients who do not accept surgical management with radical cystectomy. Preliminary results from studies such as SWOG S1605 (NCT02844816) show encouraging antitumor activity and long-lasting response patients with carcinoma in situ with or without papillary disease in terms of disease-free survival and rate free of adverse events. Recently, Keynote-057 (NCT02625961) evidenced that after 36 months of follow-up, Pembrolizumab as monotherapy was tolerable and showed promising antitumor activity in patients with BCG-unresponsive non-muscle-invasive bladder cancer.ConclusionThe checkpoint inhibitor response may offer a therapeutic alternative for patients diagnosed with high-risk non-muscle-invasive bladder cancer. However, the complete response rate documented in this scoping review is limited to patients with carcinoma in situ, with mild adverse effects, without reporting severity or death from the intervention.     

Maintenance bacillus Calmette–Guérin therapy prolongs recurrence-free survival in non-muscle-invasive bladder cancer: A real-world experience

ObjectiveWe studied the benefit of bacillus Calmette–Guérin (BCG) maintenance therapy to determine the ideal maintenance therapy schedule.MethodsWe retrospectively reviewed non-muscle-invasive bladder cancer patients who underwent transurethral resection of bladder tumors and BCG instillation treatment at Chang-Gung Memorial Hospital, Linkou, Taiwan, from January 1997 to December 2009. All patients in the study had non-muscle-invasive urothelial carcinoma of the bladder or carcinoma in situ. We compared the recurrence-free rate of patients who received induction alone and with maintenance BCG therapy sessions. In addition, we analyzed the best number of maintenance therapy sessions that gave the lowest cancer recurrence.ResultsThis study included 427 patients with a mean age of 64 years. The median number of BCG treatments was 11, and the ratio of male to female was 3:1. Receiving an induction dose alone was a significant factor for tumor recurrence with a hazard ratio of 3.77. The recurrent risk rate of patient who received BCG therapy 13–15 times had lower recurrence rate than other groups.ConclusionA maintenance dose gave patients a significant benefit over those who just received induction therapy. BCG maintenance therapy worked best if given 13–15 times in our study.     

Management of hepatic granulomatous tuberculosis complicating intravesical BCG for superficial bladder cancer

Intravesical bacille Calmette-Guérin (BCG) therapy is the most effective treatment for high-risk superficial bladder cancer. Severe systemic complications are rare, but may occur in approximately 1% of cases. We report a severe complication of intravesical BCG: a disseminated Mycobacterium bovis infection with biopsy-proven granulomatous hepatitis in a patient with bladder cancer. We also elaborate on the different management alternatives.     

Dose-response of bacillus Calmette-Guerin in the treatment of superficial bladder cancer.

Although bacillus Calmette-Guerin (BCG) has been recognized as an effective therapy for superficial bladder cancer, dose-response studies are not available. Such studies are important because the administration of the vaccine is not devoid of significant side effects when the standard dose of 120 mg. is used. It has been speculated that smaller doses may be equally effective but carry fewer side effects. A controlled study comparing 2 doses of BCG was conducted as an initial step to explore this possibility. A total of 97 patients with a diagnosis of superficial (stages TIS, Ta and T1) bladder cancer was assigned to receive either 60 or 120 mg. BCG intravesically weekly for 6 weeks. The higher dose resulted in a better response for stages TIS, Ta (for prophylaxis of recurrence) and T1. However, the differences were not statistically significant. When stage TIS and Ta tumors coexisted, a significantly better response was recorded for the high dose. The overall success for the 2 treatments was 67% and 37% for the high and low doses, respectively. These differences reached statistical significance (p less than 0.02). Side effects were significantly less in number and severity in patients receiving the smaller dose of the vaccine.     

Intravesical instillation therapy with bacillus Calmette-Guérin for superficial bladder cancer: Study of the mechanism of bacillus Calmette-Guérin immunotherapy

AIM: In order to clarify the initial step of the mechanism by which bacillus Calmette-Guérin (BCG) exhibits antitumor activity via the immune response induced in the bladder submucosa after intravesical BCG therapy for human bladder cancer, various cytokines secreted in the urine after BCG instillation were measured. METHODS: After transurethral resection of bladder cancer, a 6-week course of BCG instillation was performed. At the first and sixth weeks' dosings, spontaneously excreted urine was collected before and 4, 8, and 24 h after BCG instillation. The urinary cytokines were determined by Sandwich enzyme-linked immunosorbent assay using monoclonal antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor (TNF)-alpha, granulocyte colony-stimulating factor (G-CSF), interleukin (IL)-1beta, IL-8, interferon (IFN)-gamma, and IL-12. RESULTS: After the BCG therapy, various cytokines, such as GM-CSF, TNF-alpha, G-CSF, IL-1beta, IL-8, IFN-gamma, and IL-12 were secreted, comprising the immune response cascade. The mean urinary excretions of GM-CSF and TNF-alpha 4 h after the sixth week's instillation were significantly higher than the pre-instillation levels. There were no significant increases in the urinary IFN-gamma or IL-12 levels between 4 and 24 h after the sixth week's instillation. The TNF-alpha level 4 h after the sixth week's instillation had a strong tendency towards the absence of recurrence, with a mean follow-up of 54.1 months. The Kaplan-Meier curve showed the 2, 5, and 10-year recurrence-free survival rates were 72.4%, 65.8%, and 56.4%, respectively. CONCLUSIONS: We suggested that the urinary levels of TNF-alpha might be essential in antitumor activity after BCG therapy and might play an important role in the prevention of bladder tumor recurrence.     

Quality of life and adverse events in patients with nonmuscle invasive bladder cancer receiving adjuvant treatment with BCG,MMC, or chemohyperthermia

IntroductionChemohyperthermia (CHT) with mitomycin C (MMC) is together with Bacillus Calmette-Guérin (BCG), and passive MMC, a treatment option for patients with non muscle-invasive bladder cancer. There are no data published about the impact of CHT in quality of life (QoL). We evaluated QoL and adverse events (AE) in this 3-arm observational study.Patients and MethodsProspective observational study from September 2016 to March 2017, we recruited consecutive patients that received adjuvant treatment after transurethral resection of bladder tumor. Patients received induction courses of either BCG, CHT, or passive MMC. Patients filled the questionnaires Functional assessment of cancer therapy for bladder cancer patients (FACT-Bl) and International prostate symptom score (IPSS) before, during, and after the induction course. A urologist documented AE using Common Terminology Criteria for AE (CTCAE criteria).ResultsA total of 56 patients, receiving a total of 296 bladder instillations (BCG n = 27, CHT n = 14 and MMC n = 15). FACT-Bl showed statistically significant differences in the fourth week in favor of CHT versus BCG, IPSS did not show statistically significant differences before, during, and after induction course in all 3 arms. All patients recovered their baseline QoL at the end of the induction treatment. Overall 55.5%, 50% and 20% of patients presented any grade of AE in the BCG, CHT and MMC groups respectively. About 7% of patients in BCG and CHT arms had to discontinue treatment due to AE. BCG and CHT showed a similar rate of AE but in CHT were mostly grade I and BCG had grade I, II, and IV. Passive MMC had the safest profile.ConclusionThere are no clinically significant differences between BCG, CHT, and passive MMC regarding QoL and lower urinary tract symptoms during the induction course. CHT has a more favorable AE profile when compared with BCG.     

Intravesical bacillus Calmette-Guerin instillation therapy in superficial bladder cancers--clinical study on prognostic factors

Intravesical instillation of Tokyo 172 strain bacillus Calmette-Guerin (BCG) was performed on 137 patients with superficial bladder cancer (Ta and T1) after transurethral tumor resection as a prophylaxis against tumor recurrence. The recurrence rate of tumors was compared with that of historical controls and was estimated by the person-years method. There were statistically significant decreases in recurrent tumors following BCG therapy. To clarify the efficacy of intravesical BCG therapy, prognostic significance of several factors were evaluated in 90 patients with initial bladder cancer treated with TUR and BCG instillation, and compared to those of controls. Prophylactic effects were statistically better for those with multiple tumors, grade 3 lesions or Ta lesions than for control patients. No correlation between purified protein derivative responsiveness and favorable results could detected. There were no marked side effects or fatal complications of BCG therapy during the observation periods. Our results suggest that BCG is able to change the biological behavior of superficial bladder cancers with multiple, high grade or low stage lesions. The intravesical BCG instillation seems to be effective and safe as a prophylaxis against the recurrence of superficial bladder tumors.