Upfront bortezomib results in deep, durable haematological responses in AL amyloidosis.
A stringent dFLC response (dFLC<10mg/L) confers excellent outcomes.
Bortezomib is a standard therapy in AL amyloidosis (AL), but little is known about response duration. A difference in involved amyloidogenic and uninvolved serum free light chains (dFLC) less than 10mg/L (low-dFLC response) post-treatment predicts survival in AL patients with low presenting dFLC (20-50mg/L). We report outcomes in the largest AL cohort treated with upfront bortezomib and explore impact of post-treatment dFLC<10mg/L (a 'stringent dFLC response') in all patients. 915 newly diagnosed AL patients treated with bortezomib in the UK and assessed at our centre were included. Haematologic responses, 6 month dFLC, organ responses, overall survival (OS) and time-to-next-treatment (TNT) were evaluated. Analysis of TNT excluded patients that died without starting second-line treatment. Overall response rate (intent-to-treat) was 65%, with 49% complete response (CR)/very good partial response/low-dFLC response. The proportion of patients with a stringent dFLC response, dFLC 10-40mg/L and >40mg/L was 30%, 22% and 48%, respectively. Median OS was 72 months. 289 patients died without progressing to second-line treatment. Of the remaining patients, median TNT was not reached and 55% had not progressed to further treatment at 7 years. Patients with stringent dFLC responses had significantly better OS and TNT than those with lesser responses. 72% of CR patients did not progress to further treatment at 3 years, compared to 84% with stringent dFLC responses. Cardiac responses were better in those with stringent dFLC responses (61%) compared to lesser responses (45%), (p=0.005). Upfront bortezomib confers durable haematologic responses. A stringent dFLC response predicts prolonged TNT and impressive organ responses.