Muscle invasive bladder cancer (MIBC) is a form of bladder cancer that has progressed into the deep muscle layer of the bladder wall. This signifies a more advanced stage compared to non-muscle invasive bladder cancer, where cells remain confined to superficial layers. When cancer cells penetrate the bladder muscle, they gain a higher potential to spread to other parts of the body.
Understanding the Bladder Wall and Cancer Invasion
The bladder wall is composed of several distinct layers. The innermost layer, directly in contact with urine, is the urothelium. Beneath it lies the lamina propria, a thin layer of connective tissue. Surrounding these inner layers is the muscularis propria, a thick layer of smooth muscle also known as the detrusor muscle, which contracts to expel urine.
Non-muscle invasive bladder cancer is characterized by cancer cells remaining within the urothelium or extending only into the lamina propria. In contrast, muscle invasive bladder cancer has breached these superficial layers and infiltrated the muscularis propria. This invasion is significant because the muscularis propria is rich in blood vessels and lymphatic channels, providing a pathway for cancer cells to spread beyond the bladder.
The Diagnosis and Staging Process
Diagnosis of muscle invasive bladder cancer often begins with symptoms like painless visible blood in the urine (hematuria). Other indicators include increased urinary urgency or frequency, and discomfort during urination. These symptoms prompt a visit to a healthcare provider.
A common diagnostic procedure is a cystoscopy, where a thin, flexible tube with a camera is inserted into the bladder to visually inspect its inner lining. If abnormal growths are observed, a transurethral resection of bladder tumor (TURBT) is performed. This procedure involves removing biopsies from the bladder tumor for microscopic examination. The biopsy definitively confirms whether the cancer has invaded the muscle layer.
Following a confirmed diagnosis of muscle invasion, imaging tests determine the extent of the cancer’s spread. Computed tomography (CT) scans of the chest, abdomen, and pelvis are commonly used to check for spread to lymph nodes or distant organs. Magnetic resonance imaging (MRI) can also be utilized for more detailed local staging of the bladder.
The TNM staging system describes the cancer’s progression. “T” refers to the tumor’s depth of invasion within the bladder wall and beyond, with T2, T3, and T4 stages indicating muscle invasion. “N” denotes whether the cancer has spread to nearby lymph nodes, and “M” indicates if it has metastasized to distant parts of the body like bones, lungs, or liver.
Primary Treatment Approaches
Treating muscle invasive bladder cancer involves removing or eradicating cancerous cells to prevent further spread. One approach is radical cystectomy, the complete surgical removal of the bladder. In men, this includes the prostate and seminal vesicles; in women, it often involves removing the uterus, ovaries, and a portion of the vaginal wall.
After a radical cystectomy, urinary diversion is necessary. The two main options are an ileal conduit, which uses a segment of the small intestine to create a channel for urine to flow into a bag worn outside the body, or a neobladder, where a new internal pouch is constructed from a segment of the intestine and connected to the urethra, allowing for more natural urination.
Neoadjuvant chemotherapy is often administered before radical cystectomy. This involves using anticancer drugs, such as cisplatin-based regimens, to shrink the tumor and treat any microscopic cancer cells that may have spread beyond the bladder. This systemic treatment aims to reduce the tumor burden before surgery, potentially making surgical removal more effective.
An alternative, bladder-sparing approach for select patients is trimodal therapy. This combines a thorough transurethral resection of bladder tumor (TURBT) to remove as much visible tumor as possible, followed by concurrent chemotherapy and radiation therapy. Chemotherapy agents like cisplatin, 5-fluorouracil (5-FU), and mitomycin-C are used alongside external beam radiation therapy. This combined modality aims to preserve the bladder while achieving comparable oncologic outcomes to surgery in carefully selected individuals.
Prognosis and Long-Term Management
The outlook for individuals with muscle invasive bladder cancer depends on factors including the cancer’s stage at diagnosis, its grade, and treatment success. The five-year survival rate for stage 2 MIBC is approximately 45%, for stage 3 it is around 40%. When cancer has spread to distant sites (stage 4), the five-year survival rate is approximately 10%.
Even after primary treatment, recurrence is possible. For patients undergoing cystectomy, the cancer return rate can range from 20-30% for stage T2 tumors, increasing to 40% for T3, and over 50% for T4. In individuals treated with trimodal therapy, local recurrence is observed in approximately 20-30% of cases, with distant metastasis occurring in about 31%.
Long-term management involves a structured surveillance plan to monitor for recurrence. This includes regular cystoscopies and periodic imaging tests, such as CT or MRI scans of the chest, abdomen, and pelvis. Urine cytology, which checks for abnormal cells in the urine, can also be part of this follow-up.
Adjusting to life after treatment can involve managing changes, such as living with a urostomy (an external bag for urine collection) or a neobladder (an internal pouch). Support and guidance are available to help individuals adapt to these changes.