Session Item

Single (SRS) or multi-fraction Stereotactic Body RadioTherapy (SBRT) are effective treatment options for the treatment of oligometastatic disease of lymph nodes. Despite the encouraging local control rate, progression-free survival remains unfair due to relapses that might occur in the same district or at other sites. The recurrence pattern analysis after nodal SRS/SBRT in oligometastatic patients could pave the way for different strategies of therapeutic intensification.

This retrospective trial looks into the patterns of failure in patients with nodal metastases who were enrolled and treated with SBRT (DESTROY-1) or SRS (DESTROY-2) in 2 prospective trials at our Institution. We documented the various relapse locations of the involved lymph nodes that had been irradiated with a previous RT dose of 20 to 50 Gy in five daily fractions or 12 to 24 Gy single fraction treatment.

Data on 190 patients who received SBRT or SRS on 269 nodal lesions were reviewed. The male/female ratio was 94/96 and the median age was 66 years (range: 30-89). The most represented primary cancer was the gynaecological one (34.6%), followed by genitourinary cancer (26.7%). Pathologic lymph nodes were most frequently located in the pelvis (35.7%), followed by the thorax (34.6%) and the abdomen (24.9%) (Table 1). After SBRT/SRS the recurrences were diagnosed at imaging with a median distant metastasis-free survival (DMFS) time of 17 months (range: 3-184 months). The pattern of failure was loco-regional in 66 (42.6%) and distant in 89 (57.4%) patients, respectively. Among patients with loco-regional failure, genitourinary and gynaecological cancers were the most prevalent primary tumours, each being diagnosed in 22 (33.3%) cases. Furthermore, the predominant site of relapse (47%) was the pelvic area. Only 26% of locoregional relapses occurred contra laterally, with 74% occurring at the margin of the treatment field, or at the successive nodal station or at any nodes of the ipsilateral chain (Fig. 1). The sites of treatment which more frequently showed recurrences in neighbouring (marginal and successive) lymph node areas were the abdomen and the pelvis (41%, for both). The median follow-up of the overall series was 68 months (range 10-324 months).

Relapses following SBRT/SRS nodal irradiation were somewhat more common in distant regions than in loco-regional sites in our study. The most common scenarios for locoregional relapse appear to be genitourinary or gynaecologic cancer and the pelvic site. Additionally, recurrences are not infrequent in the immediate surrounding lymph nodal sites.