CTChart ctChart = chart.getCTChart();
CTPlotArea plotArea = ctChart.getPlotArea();
CTPieChart pieChart = plotArea.getPieChartArray(0);
//Pie Chart Series
CTPieSer ser = pieChart.getSerArray(0);
// Series Text
CTSerTx tx = ser.getTx();
tx.getStrRef().getStrCache().getPtArray(0).setV(chartTitle);
sheet.createRow(0).createCell(1).setCellValue(chartTitle);
String titleRef = new CellReference(sheet.getSheetName(), 0, 1, true, true).formatAsString();
tx.getStrRef().setF(titleRef);
// Category Axis Data
CTAxDataSource cat = ser.getCat();
CTStrData strData = cat.getStrRef().getStrCache();
// Values
CTNumDataSource val = ser.getVal();
CTNumData numData = val.getNumRef().getNumCache();
strData.setPtArray(null); // unset old axis text
numData.setPtArray(null); // unset old values