A combination of external beam radiation therapy (EBRT) and brachytherapy provides a modest survival benefit compared with brachytherapy alone for patients with intermediate prostate cancer (PCa), a new study finds.
The benefit is relatively small, so use of combined radiation therapy remains debatable in clinical practice, according to the investigators. Patients with intermediate PCa are a heterogeneous group with differing responses to treatment and there is concern about toxicities from excess radiation.
Factors such as patient age, performance status, tumor risk factors such as Gleason score, PSA level, T-stage, and percent core positivity, and risk of recurrence “must all be weighed in the decision-making process for intermediate-risk prostate cancer patients deciding between combined EBRT plus brachytherapy vs. brachytherapy alone,” lead researcher Arya Amini, MD, and colleagues at the University of Colorado School of Medicine in Aurora, concluded in Brachytherapy. Patients with co-existing conditions did not live longer with combined therapy, for example.
Using the National Cancer Database, Dr. Amini and colleagues identified 10,571 intermediate-risk PCa patients (clinical stage T2b or T2c, GS 7, or PSA 10-20 ng/mL) with no nodal involvement or metastasis. Of these, 3,148 received EBRT (40-50.4 Gy) plus brachytherapy and 7,423 received brachytherapy alone during 2004–2006. Patients receiving EBRT alone or hypofractionated EBRT were excluded.
Over a median of 7 years of follow-up, unadjusted rates of 5- and 7-year overall survival for combined radiotherapy vs. brachytherapy alone were 91.4% vs. 90.2% and 85.7% vs. 82.9%, respectively. EBRT plus brachytherapy consistently was associated with longer overall survival.
There is some concern that brachytherapy as monotherapy may not provide adequate disease control; brachytherapy techniques vary and results from previous studies have been mixed. The American Brachytherapy Society guidelines suggest that the decision to use brachytherapy alone should be considered on an individual basis. Patients at low-risk for extraprostatic extension or seminal vesicle or lymph node involvement might make good candidates. Results from the Radiation Therapy Oncology Group (RTOG) 0232 study are forthcoming and may offer additional insights on the best uses of radiotherapy in intermediate PCa, according to the investigators.
Dr. Amini’s group also found no significant survival difference with the addition of androgen deprivation therapy to radiotherapy, in contrast to previous research showing some detrimental effects.
Among the study limitations, the researchers acknowledged differences in age at baseline, inadequate information on brachytherapy dose, and incomplete information on EBRT delivery technique.