A Gleason grade is based on a pathological pattern of the glandular cells of the organ. Gleason grades 1, 2, and 3 represent lower and moderate risk tumors. Whereas, Gleason grades 4 and 5 are considered high risk. A Gleason score 7, as your father-in-law has, represents either a (3+4) or (4+3) cancer.
Prostate cancer is the most common solid male organ cancer in the US. Nearly 250,000 will be diagnosed this year. And close to 25,000 men will die of the disease this year as well. Several long-term research studies address this point about treatment versus non-treatment. I will point you towards two such studies.
Following a cohort of over 3000 men with biopsy confirmed prostate cancer. After adjusting for age, race, tumor grade, comorbid disease, income status, and year of diagnosis, the overall survival rate at 15 years was 35% for conservative management, 50% for radiotherapy, and 65% for radical prostatectomy. The corresponding prostate cancer-specific survival rates were 79%, 87%, and 92%. Patients undergoing radiotherapy or radical prostatectomy had lower overall mortality than patients undergoing conservative management (adjusted relative risk 0.67 for radiotherapy and 0.41 for prostatectomy; P <0.001). The increase in the survival duration was 4.6 years with radiotherapy and 8.6 years with radical prostatectomy (1).
Another study, which followed 4,663 men for 12-years, (37%) in the observational group and 7639 men (23.8%) in the treatment group had died. The treatment group had longer 5- and 10-year survival than the observation group. After using propensity scores to adjust for potential confounders (tumor characteristics, demographics, and comorbidities), there was a statistically significant survival advantage associated with treatment (hazard ratio, 0.69; 95% confidence interval, 0.66-0.72). A benefit associated with treatment was seen in all subgroups examined, including older men (aged 75-80 years at diagnosis), black men, and men with low-risk disease. (2)
To answer your question, the actual survival benefit is hard to quantify on a case to case basis, however, several studies show that men with biopsy confirmed prostate cancer, especially high-grade cancer, benefit from definitive treatment (radical prostatectomy).
Some signs to look out for would be urinary symptoms (frequency or urgency) and blood in the urine. It would be prudent to follow-up with a urologist.
1. Ashutosh Tewari, Jay D. Raman, Peter Chang, Sandhya Rao, George Divine and Mani Menon. Long-term survival probability in men with clinically localized prostate cancer treated either conservatively or with definitive treatment (radiotherapy or radical prostatectomy). Urology, Volume 68, Issue 6, December 2006, Pages 1268-1274.
2. Yu-Ning Wong, Nandita Mitra, Gary Hudes, Russell Localio, J. Sanford Schwartz, Fei Wan, Chantal Montagnet, Katrina Armstrong. Survival Associated With Treatment vs Observation of Localized Prostate Cancer in Elderly Men. JAMA, Vol. 296 No. 22, December 2006, Pages 2683-2693.