Functional Cure, Defined As PFS of More Than 7 Years, Is Achieved in 9% of Myeloma Patients in the Era of Conventional Chemotherapy and of First-Generation Novel Anti-Myeloma Agents; A Single-Center Experience over 20-Year Period

Advances in the management of multiple myeloma (MM) led to a significant prolongation of overall survival (OS), mainly of the younger patients; almost 10% of them experience more than 10-year OS. Although long progression-free survival (PFS) correlates with extended OS, there is very limited information for the characteristics of patients who manage to be progression-free for a long period after first-line therapy. The aim of this analysis was to evaluate the characteristics of patients who achieved at least 7-year of PFS after frontline therapy and compare them with those of all other patients who were treated in a single center during the same time period.

Between January 1994 and December 2010, 406 consecutive newly diagnosed MM patients received first line therapy in the Department of Clinical Therapeutics (Athens, Greece). All patients had symptomatic disease, based on the IMWG criteria of that period (at least one CRAB symptom to start anti-myeloma therapy). Thirty-six (8.8%; 23M/13F) patients achieved a PFS of at least 7 years (long PFS group) after frontline treatment. The median PFS of these 36 patients is 10 years, while the other patients had a median PFS of 22 months. Long PFS patients were younger (median age 56 vs 68 years; p<0.001), had bigger body surface area (median: 1.85 m2 vs. 1.76 m2; p=0.013) and lower ECOG performance status (score 0-1: 71% vs 52%; p=0.014) compared to all others. Long PFS patients had higher hemoglobin (11.4 g/dl vs 10.2 g/dl; p=0.001), higher platelet count (278 vs 224 x10⁹/l; p<0.001) and higher creatinine clearance (CrCl, based on the MDRD formula: 88 vs 67 ml/min; p<0.001; no patient in the long PFS group presented with CrCl <45 ml/min at diagnosis). There was no difference between the two groups regarding percentage of patients with high LDH, presence of osteolysis, type of myeloma (IgG vs IgA vs others), levels of serum and/or urine M-protein, and percentage of plasma cell infiltration in the bone marrow. However, more patients in the long PFS group had ISS-1 or ISS-2 disease (86% vs 61%; p=0.002) and normal pattern of marrow infiltration in the MRI of the spine and pelvis (24% vs 15%; p=0.035). Regarding chromosome abnormalities at diagnosis, no patient in the long PFS group had high-risk cytogenetics (defined as presence of del17p, t(4;14) or t(14;16) vs 32% in all other patients.

All patients received either conventional chemotherapy (CC) or first-generation novel anti-myeloma agent (bortezomib (B), thalidomide (T) or lenalidomide (R)-based regimens as frontline therapy. There was no difference between the two groups regarding CC versus novel agent-based induction treatment. Out of 36 long-term PFS patients, 11 (30%) received CC, 8 (22%) B-based, 8 (22%) RD, 6 (17%) T-based, and 3 (8%) VTD; 10 (28%) patients received first-line therapy participating in a clinical trial. Long PFS patients had received more often autologous stem cell transplantation (ASCT, 61% vs 23%; p=0.001) as part of first line therapy; therefore, more long PFS patients had also received consolidation and/or maintenance (50% vs 15%; p=0.001). Higher proportion of patients achieved at least VGPR (74% vs 41%) or at least CR (32% vs 18%) in the long PFS group. We performed next generation flow cytometry in 23 patients of the long PFS group to evaluate minimal residual disease (MRD) and 14 (61%) of them were MRD (-) at the level of the 10^-6. The probability of achieving long PFS (≥7 years) for patients who managed to be progression-free at 2, 3 and 4 years was 11.6%, 13.2% and 15.3%, respectively. In the multivariate analysis, only younger age was associated with probability for long PFS (p<0.001). The median OS of the whole group of patients was 5 years; in the long-PFS group median OS has not been reached yet while in all other patients the median OS was 4.3 years.

In conclusion, our study in an unselected group of patients, the majority of whom did not participate in clinical trials, showed that 9% of patients with newly diagnosed myeloma experience prolonged PFS of more than 7 years (median: 10 years) even in the era of CC or first-generation novel agents. These patients have low risk disease, mainly of ISS-1 or -2, no high-risk cytogenetics, no or mild renal impairment, and achieve deep responses after ASCT. These patients may be considered as "functionally" cured. The incorporation of novel treatment approaches may lead to a significant improvement in the probability of achievement of this "functionally" cured status.