Salvage Involved-Field and Extended-Field Radiation Therapy in Positron Emission Tomography-Positive Nodal Recurrent Prostate Cancer: Outcomes and Patterns of Failure

Abstract

Purpose: The optimal salvage pelvic treatment for nodal recurrences in prostate cancer is not yet clearly defined. We aimed to compare outcomes of salvage involved-field radiation therapy (s-IFRT) and salvage extended-field radiation therapy (s-EFRT) for positron emission tomography/computed tomography-positive nodal-recurrent prostate cancer and to analyze patterns of progressions after salvage nodal radiation therapy.

Methods and materials: Patients with ¹⁸F-fluorocholine or ⁶⁸Ga prostate-specific membrane antigen ligand positron emission tomography/computed tomography-positive nodal-recurrent prostate cancer and treated with s-IFRT or s-EFRT were retrospectively selected. Time to biochemical failure, time to palliative androgen deprivation therapy (ADT), and distant metastasis-free survival were analyzed.

Results: Between 2009 and 2019, 86 patients were treated with salvage nodal radiation therapy: 38 with s-IFRT and 48 with s-EFRT. After a median follow-up of 41.9 months (5.4-122.1 months), 47 patients presented a further relapse: 31 after s-IFRT and 16 after s-EFRT, with only 1 in-field relapse. The median time to palliative ADT was 24.8 months (95% confidence interval [CI], 13.3-93.5 months) in the s-IFRT group and not yet reached (95% CI, 40.3 months to not yet reached) in the s-EFRT group (P = .010). The 3-year biochemical failure-free rate was 70.2% (95% CI, 51.5%-82.9%) with s-IFRT and 73.9% (95% CI, 55.4%-85.7%) with s-EFRT (P = .657). The 3-year distant metastasis-free survival was 74.1% (95% CI, 56.0%-85.7%) with s-IFRT and 82.0% (95% CI, 63.0%-91.8%) with s-EFRT (P = .338).

Conclusions: s-EFRT and s-IFRT for positron emission tomography-positive nodal-recurrent prostate cancer provide excellent local control. Time to palliative ADT was longer following s-EFRT than following s-IFRT.

Fig. 1

Kaplan Meier analysis of probability in both treatment groups for PET-positive nodal recurrences of biochemical failure (A). Introduction of palliative androgen deprivation therapy (B) and distant metastasis (C). Abbreviations: ADT = androgen deprivation therapy; s-EFRT = salvage extended-field radiation therapy; S-IFRT = salvage involved-field radiation therapy.

Fig. 2

Migration plot showing the relationship between the location of the first nodal relapse treated with salvage extended-field or involved-field radiation therapy (left side) with the location of the second clinical relapse (right side). If a patient presented different relapse locations, he was classified in the most advanced location (defined in ascending order: local, pelvic LN, extra-pelvic LN including lumboaortic LN and supra diaphragmatic LN, bone/visceral metastases). Abbreviation: LN = lymph node.