USMLE Guide: Bladder Cancer

Introduction

Bladder cancer is a common malignancy that originates in the cells lining the inside of the bladder. It is the fourth most common cancer in men and the tenth most common cancer in women. This USMLE guide aims to provide an overview of bladder cancer, including its etiology, risk factors, clinical presentation, diagnosis, and management.

Etiology and Risk Factors

Bladder cancer is multifactorial, with several risk factors contributing to its development. The most significant risk factor is smoking, accounting for nearly half of all bladder cancer cases. Other risk factors include exposure to industrial chemicals (such as aromatic amines and polycyclic aromatic hydrocarbons), chronic bladder inflammation (e.g., from recurrent infections or bladder stones), radiation exposure, and certain genetic factors (e.g., Lynch syndrome).

Clinical Presentation

Patients with bladder cancer often present with hematuria (blood in the urine), which is typically painless and intermittent. Other symptoms may include urinary frequency, urgency, dysuria, and lower abdominal or back pain. In advanced cases, patients may experience weight loss, fatigue, and bone pain if metastasis has occurred.

Diagnosis

History and Physical Examination

A detailed history should be obtained to evaluate risk factors and symptoms. physical examination may be unremarkable in early stages but can reveal palpable bladder masses or pelvic lymphadenopathy in advanced cases.

Urinalysis

Urinalysis is essential in the workup of bladder cancer. microscopic hematuria is the most common finding, and persistent or gross hematuria should raise suspicion for malignancy. Additionally, urine cytology may show malignant cells, although it has limited sensitivity and is often used in conjunction with other diagnostic tests.

Imaging

Imaging studies are crucial for staging bladder cancer. A non-contrast CT scan can evaluate the bladder wall and detect masses or calcifications. Magnetic resonance imaging (MRI) may be used for more detailed evaluation, especially in cases where local invasion is suspected. Chest X-ray or CT scan is necessary to evaluate for lung metastasis.

Cystoscopy

Cystoscopy is the gold standard for diagnosing bladder cancer. A flexible cystoscope is inserted through the urethra to visualize the bladder, allowing direct visualization of any abnormalities. Suspicious lesions can be biopsied for histopathological examination.

Histopathology

Histopathological examination of bladder tissue is essential for diagnosis and staging. Transurethral resection of bladder tumor (TURBT) is performed to remove the tumor and obtain tissue samples. The pathologist evaluates the tumor grade (based on cellular differentiation) and stage (based on invasion depth and lymph node involvement).

Management

Non-Muscle-Invasive Bladder Cancer (NMIBC)

NMIBC includes tumors confined to the bladder mucosa or submucosa (Ta, T1, or carcinoma in situ). Treatment options include:

• Transurethral resection of bladder tumor (TURBT): Initial treatment for diagnosis and removal of visible tumors.
• Intravesical therapy: Adjuvant therapy with Bacillus Calmette-Guérin (BCG) or intravesical chemotherapy to reduce recurrence risk.
• Surveillance: Regular cystoscopy and urine cytology to monitor for recurrence.

Muscle-Invasive Bladder Cancer (MIBC)

MIBC involves tumors invading the muscular layer of the bladder (≥T2). Treatment options include:

• Radical cystectomy: Surgical removal of the bladder along with pelvic lymph node dissection. Urinary diversion is performed to maintain continence.
• Neoadjuvant chemotherapy: Administered before surgery to downstage the tumor and improve overall survival.
• Radiation therapy: May be used as an alternative to surgery in select cases or as adjuvant therapy after cystectomy.

Metastatic Bladder Cancer

Metastatic bladder cancer typically has a poor prognosis. Treatment options include:

• Chemotherapy: Systemic chemotherapy with cisplatin-based regimens is the mainstay of treatment.
• Immunotherapy: Immune checkpoint inhibitors (e.g., pembrolizumab) may be used as second-line or salvage therapy.

Conclusion

Bladder cancer is a significant cause of morbidity and mortality worldwide. Understanding the etiology, risk factors, clinical presentation, diagnosis, and management of bladder cancer is crucial for medical professionals. This USMLE guide provides a comprehensive overview to aid in the preparation for exams and enhance clinical knowledge.