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Patients of advanced age are susceptible to prostate cancer. With the current global trend of aging society, the number of elderly patients with prostate cancer is expected to increase. However, the optimal management for the elderly remains controversial. In the present study, we investigated long-term clinical outcomes of proton beam therapy (PBT) for elderly patients with localized prostate cancer.

Patients with localized prostate cancer underwent PBT in our institution between February 2010 to July 2015 were included in the present study and stratified into three groups: young, ages less than 65 years; young-old, 65 to 74 years; middle-old, 75 to 84 years. Low risk patients underwent PBT alone, while intermediate and high risk patients received neoadjuvant androgen deprivation therapy (ADT). High risk patients continued adjuvant ADT and the total period of ADT for high risk patients was three years. All the patients received a total dose of 70-78 in 28-39 fractions. Overall survival (OS), cause-specific survival (CSS) and recurrence-free (RF) rates and occurrence rates of adverse events were calculated. Late toxicities were defined according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Phoenix’s criteria of biochemical failure was adopted: a rise of ≥2 ng/mL above the nadir prostate-specific antigen after PBT, with or without ADT.

Among 152 patients enrolled in this study, 45 patients were young, 80 were young-old, and 27 were middle-old. The median follow-up time was 110 months (range, 10-142 months). 10 (6.6%) low risk patients, 33 (21.7%) favorable intermediate patients, 14 (9.2%) unfavorable intermediate patients, 71 (46.7%) high risk patients and 24 (15.8%) very high risk patients constituted this cohort. A patient died of prostate cancer and nine patients of other causes. Prostate-specific antigen (PSA) failure was observed in 11 patients. The OS rates at 5 and 10 years for young, young-old, and middle old were 97.8% and 94.8%, 97.4% and 94.4%, and 92.4% and 73.5% (p = 0.12), while the corresponding CSS rates were 100.0% and 97.0%, 100.0% and 100.0%, 100.0% and 100.0% (p = 0.27). RF rates were at 5 and 10 years for young, young-old, and middle old were 92.8% and 83.1%, 100.0% and 91.9%, 100.0% and 100.0% (p = 0.09). The cumulative incidence rate of grade 2 or worse gastrointestinal toxicities at 1, 5 and 10 years for young, young-old, and middle-old were 0.0%, 4.5% and 4.5%, 1.2%, 3.8% and 3.8%, and 0.0%, 3.7% and 3.7% (p = 0.98), while the corresponding genitourinary toxicities were 0.0%, 0.0% and 0.0%, 1.2%, 5.2% and 5.2%, and 3.7%, 3.7% and 3.7% (p = 0.33).

The current study found no significant differences in disease control rate and toxicities among young, young-old, and middle-old patients with localized prostate cancer underwent PBT. Age alone should not be a barrier to PBT for localized prostate cancer.