Prostate cancer is the most common cancer among American men, with 200,000 new cases diagnosed each year. Patients will usually consult a urological surgeon, who recommends one of three treatment plans:

surgical removal of the prostate, radiation that destroys the prostate, or watchful waiting (do nothing unless the clinical picture worsens). A biopsy is used to determine the Gleason score of the cancer, measuring its aggressiveness; Gleason scores range from 2 to 10 (higher scores correspond to more aggressive cancers). The recommended treatment will depend to some extent on biopsy results. The side effects of surgery and radiation can be drastic, and efficacy is debatable. So, as the professionals say, “management of this cancer is controversial.” However, patients tend to accept the recommendations made by their urologists.
Grace Lu-Yao and Siu-Long Yao (1997) studied treatment outcomes, using data from the Surveillance, Epidemiology and End Results (SEER)
Program. This is a cancer registry covering four major metropolitan areas and five states. The investigators found 59,876 patients who received a diagnosis of prostate cancer during the period 1983–1992, and were aged 50–79 at time of diagnosis. For these cases, the authors estimated 10-year survival rates after diagnosis. They chose controls at random from the population, matched controls to cases on age, and estimated 10-year survival rates for the controls. Needless to say, only male controls were used. Results are shown in the table below for cases with moderately aggressive cancer (Gleason scores of 5–7).

(a) How can the 10-year survival rate for the controls depend on treatment?

(b) Why does the survival rate in the controls decline as you go down the table?

(c) In the surgery group, the cases live longer than the controls. Should we recommend surgery as a prophylactic measure? Explain briefly.

(d) The 10-year survival rate in the surgery group is substantially better than that in the radiation group or the watchful-waiting group.
Should we conclude that surgery is the preferred treatment option?
Explain briefly.
10-year survival (%)
Treatment Cases Controls Surgery 71 64 Radiation 48 52 Watchful waiting 38 49