Because prostate cancer usually grows slowly, physicians sometimes recommend watchful waiting for very elderly patients or those in poor health. Doctors use PSA measurements, ultrasound and biopsy results to monitor tumor growth. With watchful waiting, no treatment is recommended until there are signs of progression. Studies have shown that men who have slow-growing cancer, other serious health problems, and life expectancies of less than 10 years, may be best suited to choose watchful waiting.