Cumulative Sum doesn't consider blank values

prasanna11289 , You should create a rank column on YYYYWW column

Have these new columns in Date Table, Week Rank is Important in Date/Week Table

Week Rank = RANKX('Date','Date'[Week Start date],,ASC,Dense)
OR
Week Rank = RANKX('Date','Date'[Year Week],,ASC,Dense) //YYYYWW format

then have a measure like this or use Windows function

Example

CALCULATE(sum('Table'[Qty]), FILTER(ALL('Date'),'Date'[Week Rank]<=max('Date'[Week Rank])))

Continue to explore Power BI Window function Rolling, Cumulative/Running Total, WTD, MTD, QTD, YTD, FYTD: https://youtu.be/nxc_IWl-tTc
https://medium.com/@amitchandak/power-bi-window-function-3d98a5b0e07f