Objective To investigate the application value of different radiotherapy modes in patients with low burden metastatic prostate cancer (LBMP).

Methods The clinical data of 91 patients diagnosed with LBMP in the 900th Hospital of the Joint Logistics Support Force of PLA from November 2009 to November 2015 were retrospectively analyzed. The average age was 53–72 (67.4±4.5) years. All patients received standard maxim androgen blockade, and 52 of them received prostate-only directed radiation therapy (PODT group), whereas 39 received prostate and metastatic radiation therapy (PMRT group). The target delineation range was prostate and bilateral seminal vesicles in the PODT group, and the total dose of the planning target volume (PTV) was 62.5 Gy (2.5 Gy per fraction, once per day, 25 fractions per 5 weeks). The target delineation range in the PMRT group was PTV combined with lymph node planning gross tumor volume (PGTV_nd) and metastatic planning gross tumor volume (PGTV_m). The total dose of PGTV_nd was 55 Gy (2.2 Gy per fraction, once per day, 25 fractions per 5 weeks). The total dose of PGTV_m was 45 Gy (1.8 Gy per fraction, once per day, 25 fractions per 5 weeks). Differences in tumor radiation volume and radiation dose to organs at risk between the groups was determined with independent sample t-test. The Expanded Prostate Cancer Index Composite and Radiation Therapy Oncology Group standards were used in evaluating the quality of life and acute radiation injury. The Mann-Whitney U rank sum test was used in comparing the two groups in terms of quality of life at various follow-up time points after radiotherapy. Acute radiation injury was compared with the chi-square test, and the Kaplan-Meier method was used for survival analysis, Log-rank χ² test was used.

Results The total radiation volume of the PODT group was (264.52±86.37) cm³, which was significantly lower than that of the PMRT group (418.47±63.64) cm³ (t=1.362, P<0.05). The radiation dose of organs at risk (rectum, bladder, left femoral head, and right femoral head) in the PODT group were significantly lower than those in the PMRT group (t=2.01–4.78, all P<0.05). The scores of urinary system function in the PODT group 1 day, 3 months, and 6 months after radiotherapy were significantly higher than those in the PMRT group (Z=4.467, 5.726, 7.984; all P<0.05). The scores of intestinal system function in the PODT group were significantly higher than those in the PMRT group (Z=3.826, 5.693, 7.874; all P<0.05). The sexual function score of the PMRT group was higher than that of the PODT group at each follow-up point 3 months after radiotherapy (Z=2.381–9.872, all P<0.05). No significant differences in five-year overall survival rate and prostate cancer specific survival rate were found between the groups (χ²=4.62, 3.07; both P>0.05). The PODT group had a lower five-year interval to biochemical failure (IBF) rate than the PMRT group (4.2% vs. 14.9%), and the difference was significant (χ²=7.68, P=0.03). The incidence rates of leukopenia, thrombocytopenia, and hemoglobin decline in the PMRT group were significantly higher than those in the PODT group (χ²=6.09, 3.12, 7.58; all P<0.05). The results were consistent with the incidence of vomiting (χ²=8.93, P<0.05).

Conclusions Compared with patients who received PODT, patients who received PMRT showed increased IBF time but did not show increases in PCSS and OS time. The incidence of radiation injury increased in the PMRT group.