Improved Prognosis in Multiple Myeloma-a Population Based Study on 13,376 Patients Diagnosed in Sweden 1973–2001.
Authors: Kristinsson Sigurdur Y. , Landgren Ola , Dickman Paul , Derolf Asa , Bjorkholm Magnus 
Published: October 2019

Abstract
Background:
Over the last decades there have been advances in the treatment of patients with multiple myeloma (MM) and prognosis has improved with the introduction of new treatment strategies. However, few studies have addressed the issue which patients benefit most from these therapeutic changes over the years.
Aims:
To evaluate relative survival in all diagnosed MM patients in Sweden 1973–2001 and relate the changes to age, sex and type of hospital where diagnosis was made.
Methods:
All patients with MM notified to the Swedish Cancer Register in 1973–2001 were followed up by record linkage to the nationwide Cause of Death Register. Survival analyses were performed by obtaining relative survival (RS) defined as the ratio of observed versus expected survival. The study period was divided arbitrarily to four calendar periods: 1973–1979, 1980–1986, 1987–1993, and 1994–2002. Patients were grouped according to age at diagnosis (0–40, 41–50, 51–60, 61–70, 71–80, and 80+), sex, and hospital category. RS was estimated using SAS (Cary, NC, USA) and excess mortality modelled using Poisson regression.
Results:
A total of 13,376 patients (7,114 males and 6,262 females, mean age 69.8 years, and 32% diagnosed at a university hospital) were diagnosed with MM in Sweden between January 1st 1973 and December 31st 2001. The overall one-year RS estimates were 73%, 78%, 80%, and 81%, respectively, for the four calendar periods. The overall five-year RS was 31%, 32%, 34%, and 36% and the ten-year RS remained stable at 12%, 11% 13% in the first three periods; ten-year RS could not be calculated for the last calendar period.
The increase in one-year RS was observed in all age categories over the four calendar periods, while the increase in five-year RS was restricted to patients <70 years. Younger age at onset was associated with a superior survival in all calendar periods. Differences in survival by age at diagnosis and calendar period were highly statistically significant (p<0.0001). Females had a superior 1- (p=0.002), 5- (p=0.024), and 10-year RS (p=0.019) compared to males, after adjusting for age and period. Patients diagnosed at university hospitals had superior 5- and 10-year RS (p=0.007) but not 1-year RS.
Summary/conclusions: The present study shows an improved prognosis over time in a population-based study including > 13,000 MM patients diagnosed during a 29-year period. Of interest is that even one-year RS has improved in all age groups over the whole study period. Increase in five-year RS was only observed in patients aged <70 years. The ten-year RS did not improve over the first 20 years and could not be estimated for patients diagnosed in the last period. Younger age at diagnosis was associated with superior one-, five- and ten-year RS in all calendar periods.
Females had a significantly better survival than males. A significant difference in survival was seen according to type of hospital, with patients diagnosed at a university hospital surviving longer. In conclusion, the results show that survival of MM patients has improved during the study period. However, long-term survival has not improved significantly. Males, elderly patients and patients diagnosed during early calendar periods experienced higher excess mortality.