Bacillus Calmette Gurin BCG

The anti-neoplastic effect of the live attenuated tuberculosis vaccine, bacillus Calmette-Guérin (BCG), was reported by Pearl in 1929. Later, Mathe and co-workers demonstrated a survival benefit in animals with haematological malignancies treated with BCG. Unfortunately, the clinical studies that followed did not confirm any effectiveness of BCG systemic administration in patients with various malignancies (lymphocytic leukaemia, melanoma, lung cancer). Currently, only two applications of BCG in cancer patients are successful:

♦ Intralesional administration into cutaneous metastases in patients with melanoma

♦ Intravesical instillation for the treatment of patients with superficial bladder cancer

Immunotherapeutic action of BCG

♦ Activates—macrophages

—T lymphocytes — B lymphocytes —natural killer cells

♦ Induces local type II immunological responses via interleukins (IL-4, IL-1, IL-10)

♦ Bacterial surface glycoproteins attach to epithelial cells and act as antigens

♦ Inhibits tumour-cell motility via BCG—fibronectin

—tumour interaction BCG is the most effective intravesical agent for the prophylaxis of Ta and T1 superficial bladder cancer, with a 38% reduction of recurrence rate. It can also achieve a complete response rate of 60% or more in stage Ta or T1 residual bladder cancer, although it is generally preferable to resect all visible tumours when possible, prior to beginning treatment.

Immunotherapy, in the form of BCG, is the only approved intraves-ical treatment for CIS (carcinoma in situ), with an average complete response rate of 72% (vs < 50% for chemotherapy).

The optimal dose and schedule of administration of BCG varies from patient to patient: the proposed intravesical dose is between one hundred million (1 x 108) and one billion (1 x 1010) colony forming units (CFU), but responses have been reported with doses as low as 10 million CFU or 1 mg BCG.

Many patients (up to 90%) experience symptoms of cystitis, with dysuria, haematuria, mild fever, and urinary frequency. It is advisable to withhold BCG administration to patients with gross haematuria, because the risk for absorption and major systemic BCG toxicity is increased. The most serious complication of BCG therapy is sepsis. It is mediated by traumatic catheterization with bleeding, severe cystitis, bladder biopsy, or transurethral resection of bladder tumour. Sepsis from gram-negative bacillae may occur following instrumentation of the genitourinary tract.

Nevertheless, treatment must be initiated on the basis of medical history of BCG instillation and of clinical suspicion: patients typically, but not invariably, develop:

Hypertension

♦ Mental confusion

♦ Disseminated intravascular coagulopathy

♦ Respiratory failure

♦ Leukopenia

Identification of BCG DNA with techniques of molecular biology may prove useful in the future.

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