Mutual Fund Summary Prospectus (497k)

Rule 497 (k)
File No. 333-140895

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AlphaDEX(R)
Family of ETFs

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SUMMARY PROSPECTUS

First Trust Mega Cap AlphaDEX(R) Fund

Ticker Symbol: FMK
Exchange: NYSE Arca, Inc.

Before you invest, you may want to review the Fund's prospectus, which contains more information about the Fund and its risks. You can find the Fund's prospectus and other information about the Fund, including the statement of additional information and most recent reports to shareholders, online at http://www.ftportfolios.com/retail/ETF/ETFfundnews.aspx?Ticker=FMK. You can also get this information at no cost by calling [phone] or by sending an e-mail request to [e-mail]. The Fund's prospectus and statement of additional information, both dated November 30, 2012, are all incorporated by reference into this Summary Prospectus.

INVESTMENT OBJECTIVE

The First Trust Mega Cap AlphaDEX(R) Fund (the "Fund") seeks investment results that correspond generally to the price and yield (before the Fund's fees and expenses) of an equity index called the Defined Mega Cap Index (the "Index").

FIRST TRUST November 30, 2012

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FEES AND EXPENSES OF THE FUND

The following table describes the fees and expenses you may pay if you buy and hold Shares of the Fund. Investors purchasing and selling Shares may be subject to costs (including customary brokerage commissions) charged by their broker.

<CAPTION> <S> <C> SHAREHOLDER FEES (fees paid directly from your investment) Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) None ANNUAL FUND OPERATING EXPENSES (Expenses that you pay each year as a percentage of the value of your investment) Management Fees 0.70% Distribution and Service (12b-1) Fees 0.00% Other Expenses 0.00% -------- Total Annual Fund Operating Expenses 0.70%

EXAMPLE

The example below is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. This example does not take into account customary brokerage commissions that you pay when purchasing or selling Shares of the Fund in the secondary market.

The example assumes that you invest $10,000 in the Fund for the time periods indicated and then you retain the Shares or sell all of your Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain at current levels. Additionally, the example assumes that the Fund imposes a 12b-1 fee of 0.25% per annum of the Fund's average daily net assets following November 30, 2013. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

1 YEAR 3 YEARS 5 YEARS 10 YEARS
$72 $269 $493 $1,135

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 164% of the average value of its portfolio.

PRINCIPAL INVESTMENT STRATEGIES

The Fund will normally invest at least 90% of its net assets in common stocks that comprise the Index. The Fund, using an "indexing" investment approach, attempts to replicate, before fees and expenses, the performance of the Index. First Trust seeks a correlation of 0.95 or better (before fees and expenses) between the Fund's performance and the performance of the Index; a figure of 1.00 would represent perfect correlation. First Trust will regularly monitor the Fund's tracking accuracy and will seek to maintain an appropriate correlation.

The Index is in the "Defined Index Series," a family of custom enhanced indices developed, maintained and sponsored by S&P Dow Jones Indices LLC ("S&P" or an "Index Provider"). The Index is a modified equal-dollar weighted index designed by S&P to objectively identify and select stocks from the S&P BMI US Index that may generate positive alpha relative to traditional passive-style indices through the use of the AlphaDEX(R) selection methodology. Alpha is an indication of how much an investment outperforms or underperforms on a risk-adjusted basis relative to its benchmark. The securities of companies represented in the Index have market capitalizations that are consistent with the name of the Index. As of July 31, 2012, the Index was comprised of 50 securities and the market capitalization range represented in the index was approximately $30.9 billion to $572.5 billion. The Index is rebalanced and reconstituted as of the last business day of each calendar quarter. Changes to the Index will be effective at the open of trading on the sixth business day of the following month.

PRINCIPAL RISKS

You could lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

MARKET RISK. Market risk is the risk that a particular stock owned by the Fund, Shares of the Fund or stocks in general may fall in value. Shares are subject to market fluctuations caused by such factors as economic, political, regulatory or market developments, changes in interest rates and perceived trends in stock prices. Overall stock values could decline generally or could underperform other investments.

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NON-CORRELATION RISK. The Fund's return may not match the return of the Index for a number of reasons. For example, the Fund incurs operating expenses not applicable to the Index, and may incur costs in buying and selling securities, especially when rebalancing the Fund's portfolio holdings to reflect changes in the composition of the Index. In addition, the Fund's portfolio holdings may not exactly replicate the securities included in the Index or the ratios between the securities included in the Index.

REPLICATION MANAGEMENT RISK. The Fund is exposed to additional market risk due to its policy of investing principally in the securities included in the Index. As a result of this policy, securities held by the Fund will generally not be bought or sold in response to market fluctuations and the securities may be issued by companies concentrated in a particular industry. Therefore, the Fund will generally not sell a stock because the stock's issuer is in financial trouble, unless that stock is removed or is anticipated to be removed from the Index.

NON-DIVERSIFICATION RISK. The Fund is classified as "non-diversified" under the Investment Company Act of 1940, as amended (the "1940 Act"). As a result, the Fund is only limited as to the percentage of its assets which may be invested in the securities of any one issuer by the diversification requirements imposed by the Internal Revenue Code of 1986, as amended (the "Code"). The Fund may invest a relatively high percentage of its assets in a limited number of issuers.

INDEX TRACKING RISK. You should anticipate that the value of Fund Shares will decline, more or less, in correlation with any decline in the value of that Fund's Index.

MARKET CAPITALIZATION RISK. The securities of companies represented in the Index have market capitalizations that are consistent with the name of the Index. For purposes of determining the market capitalization range of such securities, the Fund will use the current range of the Index. However, the Fund will not be forced to sell a stock because the stock has exceeded or fallen below the current market capitalization range of the Index. Because of market movement, there can be no assurance that the securities in the Fund will stay within a given market capitalization range. As a result, the Fund may be exposed to additional risk or may not give investors the opportunity to invest fully in a given market capitalization range.

ANNUAL TOTAL RETURN

The Fund has not yet operated for a full calendar year and, therefore, performance information is not included in this section of the Prospectus. See "Total Return Information" for performance information regarding the Fund.

MANAGEMENT

INVESTMENT ADVISOR
First Trust Advisors L.P. ("First Trust")

PORTFOLIO MANAGERS

The Fund's portfolio is managed by a team (the "Investment Committee") consisting of: Daniel J. Lindquist, Chairman of the Investment Committee and Senior Vice President of First Trust; Jon C. Erickson, Senior Vice President of First Trust; David G. McGarel, Chief Investment Officer and Senior Vice President of First Trust; Roger F. Testin, Senior Vice President of First Trust; and Stan Ueland, Vice President of First Trust. Each Investment Committee member has served as a part of the portfolio management team of the Fund since inception.

PURCHASE AND SALE OF FUND SHARES

The Fund issues and redeems Shares on a continuous basis, at NAV, only in Creation Units consisting of 50,000 Shares. The Fund's Creation Units are issued and redeemed principally in-kind for securities included in the Fund's portfolio. Individual Shares may only be purchased and sold on NYSE Arca through a broker-dealer. Shares of the Fund will trade on NYSE Arca at market prices rather than NAV, which may cause the Shares to trade at a price greater than NAV (premium) or less than NAV (discount).

TAX INFORMATION

The Fund's distributions are taxable and will generally be taxed as ordinary income or capital gains.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

If you purchase the Fund through a broker-dealer or other financial intermediary (such as a bank), First Trust and First Trust Portfolios L.P., the Fund's distributor, may pay the intermediary for the sale of Fund Shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.

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FMKSP0113012