Parsing JSON Web Request to txt file

Hi people trying to compile this web request here: http://csgobackpack.net/api/GetItemsList/v2/?no_details . Here is the js code I am using

updateMarketPrices();
function updateMarketPrices() {

    request('http://csgobackpack.net/api/GetItemsList/v2/?no_details', function(error, response, body) {
        prices = JSON.parse(body);
        prices['migration_time_validation'] = JSON.stringify(database_params);
        if(prices.response.success == true) {
            logger.warn('Loaded fresh prices');
            if(fs.existsSync('/var/www/prices.txt')){
                prices = JSON.parse(fs.readFileSync('/var/www/prices.txt'));
                logger.warn('Prices loaded from cache');
            } else {
                logger.error('No prices in cache');
                process.exit(0);
            }
        } else {
            fs.writeFileSync('/var/www/prices.txt', body);
            logger.trace('New prices loaded');
        }
    });
}

using these npm packages:

var request = require('request');
var fs = require('fs');

The return I am getting is:

 if(prices.response.success == true) {
                                   ^

TypeError: Cannot read property 'success' of undefined
    at Request._callback (/home/bot/prices.js:52:22)
    at Request.self.callback (/home/bot/node_modules/request/request.js:185:22)
    at Request.emit (events.js:314:20)
    at Request.<anonymous> (/home/bot/node_modules/request/request.js:1154:10)
    at Request.emit (events.js:314:20)
    at IncomingMessage.<anonymous> (/home/bot/node_modules/request/request.js:1076:12)
    at Object.onceWrapper (events.js:420:28)
    at IncomingMessage.emit (events.js:326:22)
    at endReadableNT (_stream_readable.js:1241:12)
    at processTicksAndRejections (internal/process/task_queues.js:84:21)

What could you suggest thanks people...