High dose chemotherapy and stem cell rescue for aggressive non-Hodgkin's lymphoma: Pattern of failure and implications for involved-field radiotherapy

Purpose: To evaluate the pattern of failure and outcome of patients with aggressive non-Hodgkin's lymphoma (NHL) undergoing high-dose chemotherapy (HDCT) and autologous stem cell rescue (SCR) with an emphasis on the role of adjuvant involved-field radiotherapy (IFRT). Method and Materials: Fifty- three adult patients with aggressive NHL (46 intermediate- and 7 high-grade) underwent HDCT with SCR. All patients underwent induction chemotherapy prior to high dose intensification. Seven (13.2%) received IFRT to 10 disease sites either prior to or following HDCT. Indication included symptomatic or bulky disease, persistent disease, or to consolidate a complete response (CR). Sites of relapse were designated as old (involved prior to HDCT) or new (previously uninvolved). Median follow-up was 20.1 months (range, 1.2-69,3 months). Results: The 4-year actuarial progression-free (PFS) and cause- specific (CSS) survivals of the entire group were 30.0 and 50.2%, respectively. Excluding toxic deaths, 24 patients (52.2%) relapsed. Sixteen (34.7%) failed in old and 15 (32.6%) in new sites. Patients treated with IFRT had a lower rate of relapse in old sites (0 vs. 41%) (p = 0.04) than patients treated with HDCT alone. Of the 141 sites present prior to induction, 127 (90.1%) were amenable to IFRT. Excluding irradiated sites, the overall 4- year local control (LC) of all amenable sites was 61.1%. Amenable sites failing to achieve a CR to induction had a poorer LC (32.0 vs. 95.1%) (p < 0.0001) than sites in CR. The 4-year LC of sites failing to achieve a CR to HDCT was 29.4%. Adjuvant IFRT improved the 4-year LC of all sites (100 vs. 61.1%) (p = 0.05), persistent sites following induction (100 vs. 32.0%) (P = 0.01) and persistent sites following HDCT (100 vs. 29.4%) (p = 0.01). Adjuvant IFRT was not associated with any untoward acute or late toxicity. Conclusions: The predominant site of relapse in patients with aggressive NHL undergoing HDCT and SCR is in sites of disease present prior to HDCT. However, the risk of relapse of prior disease sites varies greatly depending upon their response to chemotherapy. Sites at greatest risk are those failing to achieve a CR to induction regardless of their response to HDCT. IFRT is capable of reducing the high risk of relapse in these sites, the majority of which are amenable to IFRT. These results demonstrate a rationale for and possible benefit to IFRT in patients with aggressive NHL undergoing HDCT and SCR.