Nodal Oligorecurrent Prostate Cancer: Anatomic Pattern of Possible Treatment Failure in Relation to Elective Surgical and Radiotherapy Treatment Templates

Abstract

BackgroundPatients with biochemical recurrence following primary prostate cancer (PCa) treatment often experience relapse in the lymph nodes (LNs). Both salvage LN dissection (sLND) and elective nodal radiotherapy (ENRT) are potential treatment options. ObjectiveTo describe anatomic patterns of nodal oligorecurrent PCa in relation to different surgical and radiotherapy templates. Design, setting, and participantsPatients with biochemical recurrence following primary PCa treatment were eligible for 18F-choline positron emission tomography/computed tomography (CT). Patients with five or fewer LN recurrences (N1/M1a) were eligible for the current retrospective analysis. Outcome measurements and statistical analysisAll LN recurrences were mapped on a reference patient CT, as well as different surgical templates (limited to superextended) and an adapted version of the PIVOTAL ENRT template, blinded for the recurrences. Descriptive statistics were used to report recurrences in relation to the different templates and to compare LN coverage between templates. Results and limitationsIn total, 158 LN recurrences (N1: 88; M1a: 70) in 82 patients (median age: 67yr; prostate-specific antigen [PSA]: 3.1ng/ml; PSA doubling time of 7.8mo at the time of clinical recurrence) were mapped. In 49% of patients, recurrences were exclusively located in the true pelvis, followed by the common iliac LN (10%), retroperitoneal/inguinal LN (10%), or a combination (31%). There was up to 40% volume overlap between ENRT and the surgical templates. Theoretically, with ENRT more patients are fully covered (p<0.02) and the total number of covered lesions is higher (p<0.001) when compared to all types of sLND, except for superextended sLND, which is comparable to ENRT (patient-level: p=0.6; lesion-level: p=0.09). With 22% of all 158 lesions located outside all templates (N1: 7%; M1a: 15%), at least 31% of all 82 patients would not be salvaged using any of the templates. ConclusionsMore than half of nodal recurrences are located outside the true pelvis. Limited or standard extended sLND is considered insufficient as a salvage treatment approach and is thus not recommended for use. To maximize treatment outcomes for nodal recurrences, ENRT or superextended sLND should be preferred. Patient summaryWe compared two possible treatment options, elective nodal radiotherapy and salvage lymph node dissection, for patients with prostate cancer recurrence limited to five or fewer lymph nodes and reported the nodal distrubution. Radiotherapy and surgery cover different areas with possible different outcomes.