Incidence and prevalence are closely related. Prevalence is the measure of a condition (or disease) in a population at a given point in time (point prevalence) though it can also be measured over a period of time (e.g. a year), when it is called period prevalence. Incidence is the number of new occurrences of a condition (or disease) in a population over a period of time. Both measures of prevalence are proportions (i.e. lack any unit) and should not be described as rates.
Prevalence (the proportion of a population with a problem at a designated time) depends on both the incidence (the rate of new problem during a period of time) and the duration of the problem. Incidence is useful in understanding how commonly a disease or problem occurs over a period of time and this can be used to estimate ones risk of getting the disease. Recovery or death will reduce the prevalence. The prevalence of chronic disease in general population is growing because of both the higher incidence of chronic disease (there are more cases each year than in the past) and the longer survival of patients with chronic disease resulting from modern treatments. If death rates drop, then the time that patients live with chronic disease grows and even a low incidence will produce a high prevalence. Prevalence is a more relevant measure than incidence when assessing the impact or extent of a problem (or disease) within a community and to assess the subsequent needs and thus has implications to the provision of services needed in a community. Data on prevalence are easier to collect than incidence data.
The First All India Report: 2001-2002 (National Cancer Registry Programme, ICMR) does not give the incidence of these two disorders. The reported annual incidence of multiple myeloma in India ranges from 0.5 to 1.2 per 100,000 while the GLOBOCAN: Cancer Incidence, Mortality and Prevalence Worldwide mentions it to be 6 per million. No data is available on myelodysplastic syndromes in India though in Western literature it is annual incidence is 0.5-4 per million population.
Lenalidomide is an immunomodulatory derivative chemically similar to thalidomide but is more potent and has a different side effect profile than thalidomide. A number of lenalidomide clinical trials are being conducted in patients with relapsed/refractory or newly-diagnosed multiple myeloma and it is also being tried as maintenance therapy. The drug (in combination with dexamethasone) is now a recommended option for initial therapy in transplant candidates in the National Comprehensive Cancer Network Clinical Practice Guidelines for multiple myeloma and it is also combined with melphalan and dexamethasone for use in patients not eligible for transplant. It has been used as a single 25 mg capsule on days 1 to 21 of repeated 28-day cycles for 4 to 9 cycles. The dose is continued or modified based upon clinical and laboratory findings (platelets <30,000/ml or neutrophils <1,000/ml).
Lenalidomide is indicated for transfusion-dependent myelodysplastic syndromes (MDS) subtype of deletion 5q cytogenetic abnormality. It shows substantial activity in patients with MDS who do not respond to treatment with erythropoietin or who have high endogenous erythropoietin levels and therefore are unlikely to benefit from erythropoietin treatment. The dose used is much lower than that used in myeloma and patients showing a response continue taking the drug until disease progression, treatment failure, or dose-limiting adverse events occur.