Split-course RT valuable after hormone-resistant prostate cancer relapse

By Sarah Guy

A split course of high-dose radiotherapy (RT) in men with progressive, hormone-refractory prostate cancer (HRPC) is effective and has an acceptable toxicity profile, report Australian researchers.

The two-phase 45-60 Gy regimen given in 18-24 fractions with a 2-week break in between resulted in 91% of the cohort achieving a clinical response within 3 months, they say.

Furthermore, overall survival was 28 months' post-treatment, with no reports of high-grade toxicity (grade 3 or 4 on the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer scoring criteria).

Nirdosh Kumar Gogna, from the Mater Centre in Brisbane, Queensland, and co-workers remark that their results compare with those of other studies of high-dose RT in the HRPC setting, but that the "key difference" is that "this treatment schedule required fewer treatment visits, an important consideration in administering palliative treatment."

Gogna and colleagues reviewed data for 34 patients with HRPC who had become resistant to androgen deprivation therapy after a median 42 months. The men presented with urinary tract symptoms (61.7%), isolated rectal symptoms (2.9%), or a combination of both symptoms (35.2%), indicating local progression of disease.

Three months after undergoing the two-phase RT regimen to address their presenting symptoms, 19 (56%) patients experienced a major response (defined as significant improvement in all domains to complete resolution of presenting symptoms), and 12 (35%) experienced a partial response (defined as at least a 50% improvement in symptoms).

After an initial period of stabilization, the remaining three patients' disease progressed fairly quickly, write Gogna et al in the International Journal of Radiation Oncology Biology Physics.

There were no significant differences in response rates per initial patient symptom type, they add.

The team followed patients up further in 3-6-month intervals over a median period of 24 months, and those who had developed HRPC within 12 months of initiating androgen deprivation had poorer outcomes than those who developed it later, dying of distant and/or locally progressive disease within 12 months.

The median overall progression-free survival in the cohort was 43 months, and the median overall survival was 28 months.

Sixteen (48%) and 11 (30%) patients experienced grade 1 or 2 urinary and lower gastrointestinal symptoms, respectively, and two (6%) patients underwent temporary catheterization, observes the research team.

However, no other acute grade 3 or 4 toxicities were reported, and likewise, no late (post-12 months) grade 3 or 4 toxicities were reported.

"The split-course, high-dose RT regimen not only achieved patient expediency, convenience, and tolerability, but also provided efficacy and durability of response," conclude Gogna and co-investigators.

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