Rule 497 (k)
                                                             File No. 333-140895

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                                                                     AlphaDEX(R)
First Trust Mega Cap AlphaDEX(R) Fund                             Family of ETFs
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SUMMARY PROSPECTUS:            TICKER:              EXCHANGE:
April 8, 2016                  FMK                  The Nasdaq Stock Market LLC
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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 (800) 621-1675 or by sending an
e-mail request to info@ftportfolios.com. The Fund's prospectus and statement of
additional information, both dated April 8, 2016, are all incorporated by
reference into this Summary Prospectus.

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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 Nasdaq AlphaDEX(R) Mega Cap Index (the
"Index").

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,
which are not reflected in the table below.

SHAREHOLDER FEES (fees paid directly from your investment)
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Maximum Sales Charge (Load) Imposed on Purchases (as a
   percentage of offering price)                                          None
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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(1)                             0.00%
     Other Expenses                                                       0.00%
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     Total Annual Fund Operating Expenses                                 0.70%
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(1)   Although the Fund has adopted a 12b-1 plan that permits it to pay up to
      0.25% per annum, it will not pay 12b-1 fees any time before April 7, 2017.



                                                                     FIRST TRUST
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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. 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 April 7, 2017. 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
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       $72                  $278                 $501                 $1,144
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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 Fund
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 134%
of the average value of its portfolio.

PRINCIPAL INVESTMENT STRATEGIES

The Fund will normally invest at least 90% of its net assets (including
investment borrowings) 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. The Fund's investment advisor 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. The Index is owned and is developed, maintained and
sponsored by Nasdaq, Inc. (the "Index Provider").

The Index is designed to select mega cap stocks from the NASDAQ US 500 Large Cap
Index (the "Base Index") that may generate positive alpha, or risk-adjusted
returns, relative to traditional 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 Index attempts to generate positive alpha by identifying stocks based on
three factors: value, momentum and size.

The Base Index is a comprehensive, rules-based index designed to measure stock
market performance of large cap US companies, as determined by the Index
Provider. The Fund will be concentrated in an industry or a group of industries
to the extent that the Index is so concentrated.

Security selection for the Index will be conducted in the following manner:

   1. The selection universe for the Index begins with all stocks in the Base
      Index.

   2. The Index Provider then removes any stocks which do not trade on an
      eligible exchange; duplicate (multiple share classes) stocks; and stocks
      which do not meet the Index Provider's liquidity screens.

   3. The remaining stocks are then ranked by market capitalization. The top 100
      largest stocks by market capitalization, which the Index Provider defines
      as "mega cap," are eligible for the portfolio.

   4. The remaining stocks in the universe are then ranked on both growth and
      value factors. A stock's selection score is the better of the growth or
      value rank.

   5. The top 50 stocks based on the selection score determined in step 4
      comprise the "selected stocks." The selected stocks are then split into
      quintiles based on their selection score, with higher scoring quintiles
      receiving a greater weight in the Index, subject to sector constraints.

The Index is reconstituted and rebalanced quarterly and the Fund will make
corresponding changes to its portfolio shortly after the Index changes are made
public. The inception date of the Index was January 11, 2016. As of February 29,
2016, the Index was composed of 50 securities. See "Index Information" for
additional information.

The Fund's strategy includes a quarterly portfolio rebalance and reconstitution
which may result in a high rate of turnover. As of February 29, 2016, the Fund
had significant investments in consumer discretionary and information technology
companies. The securities of companies represented in the Index generally have
market capitalizations that are consistent with the name of the Index. To
determine the market capitalization range of such securities, the Fund uses the
current range of the Index. However, the Fund will not sell a security because
the security has exceeded or fallen below the current market capitalization
range of the Index. As of February 29, 2016, the market capitalization range of
securities in the Index was $28.3 billion to $539 billion.

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. There can be no
assurance that the Fund's investment objective will be achieved.

CONSUMER DISCRETIONARY COMPANIES RISK. Consumer discretionary companies are
companies that provide non-essential goods and services, such as retailers,
media companies and consumer services. These companies manufacture products and
provide discretionary services directly to the consumer, and the success of
these companies is tied closely to the performance of the overall domestic and
international economy, interest rates, competition and consumer confidence.
Success depends heavily on disposable household income and consumer spending.
Changes in demographics and consumer tastes can also affect the demand for, and
success of, consumer discretionary products in the marketplace.

EQUITY SECURITIES RISK. Because the Fund invests in equity securities, the value
of the Fund's shares will fluctuate with changes in the value of these equity
securities. Equity securities prices fluctuate for several reasons, including
changes in investors' perceptions of the financial condition of an issuer or the
general condition of the relevant stock market, such as market volatility, or
when political or economic events affecting the issuers occur. In addition,
common stock prices may be particularly sensitive to rising interest rates, as
the cost of capital rises and borrowing costs increase.

GROWTH STOCKS INVESTMENT RISK. Growth stocks tend to be more volatile than
certain other types of stocks and their prices usually fluctuate more
dramatically than the overall stock market. A stock with growth characteristics
can have sharp price declines due to decreases in current or expected earnings.





INDEX CONSTITUENT RISK. The Fund may be a constituent of one or more indices. As
a result, the Fund may be included in one or more index-tracking ETFs or mutual
funds. Being a component security of such a vehicle could greatly affect the
trading activity involving the Fund, the size of the Fund and the market
volatility of the Fund. Inclusion in an index could significantly increase
demand for the Fund and removal from an index could result in outsized selling
activity in a relatively short period of time. As a result, the Fund's net asset
value could be negatively impacted and the Fund's market price may be
significantly below the Fund's net asset value during certain periods. In
addition, index rebalances may potentially result in increased trading activity.
To the extent buying or selling activity increases, the Fund can be exposed to
increased brokerage costs and adverse tax consequences and the market price of
the Fund can be negatively affected.

INFORMATION TECHNOLOGY COMPANIES RISK. Information technology companies are
generally subject to the risks of rapidly changing technologies, short product
life cycles, fierce competition, aggressive pricing and reduced profit margins,
loss of patent, copyright and trademark protections, cyclical market patterns,
evolving industry standards, and frequent new product introductions. Information
technology companies may be smaller and less experienced companies, with limited
product lines, markets or financial resources and fewer experienced management
or marketing personnel. Information technology company stocks, particularly
those involved with the Internet, have experienced extreme price and volume
fluctuations that often have been unrelated to their operating performance.

MARKET CAPITALIZATION RISK. 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.

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

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.

PORTFOLIO TURNOVER RISK. High portfolio turnover may result in the Fund paying
higher levels of transaction costs and generating greater tax liabilities for
shareholders. Portfolio turnover risk may cause the Fund's performance to be
less than you expect.

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.

VALUE STOCKS INVESTMENT RISK. The intrinsic value of a stock with value
characteristics may not be fully recognized by the market for a long time or a
stock judged to be undervalued may actually be appropriately priced at a low
level.

ANNUAL TOTAL RETURN

The bar chart and table below illustrate the annual calendar year returns of the
Fund based on net asset value as well as the average annual Fund and Index
returns. The bar chart and table provide an indication of the risks of investing
in the Fund by showing changes in the Fund's performance from year-to-year and
by showing how the Fund's average annual total returns based on net asset value
compare to those of the Index and a broad-based market index. On April 8, 2016,
the Fund's underlying index changed from the Defined Mega Cap Index to the
Nasdaq AlphaDEX(R) Mega Cap Index. Therefore, the Fund's performance and
historical returns shown below are not necessarily indicative of the performance
that the Fund, based on the Index, would have generated. Returns for an
underlying index are only disclosed for those periods in which the index was in
existence for the whole period. Because the Fund's new underlying index had an
inception date of January 11, 2016, it was not in existence for any of the
periods disclosed. The new Index is substantially similar to the Defined Mega
Cap Index. See "Total Return Information" for additional performance information
regarding the Fund. The Fund's performance information is accessible on the
Fund's website at www.ftportfolios.com.

Returns before taxes do not reflect the effects of any income or capital gains
taxes. All after-tax returns are calculated using the historical highest
individual federal marginal income tax rates and do not reflect the impact of
any state or local tax. Returns after taxes on distributions reflect the taxed
return on the payment of dividends and capital gains. Returns after taxes on
distributions and sale of shares assume you sold your shares at period end, and,
therefore, are also adjusted for any capital gains or losses incurred. Returns
for the market index do not include expenses, which are deducted from Fund
returns, or taxes.

Your own actual after-tax returns will depend on your specific tax situation and
may differ from what is shown here. After-tax returns are not relevant to
investors who hold Fund shares in tax-deferred accounts such as individual
retirement accounts (IRAs) or employee-sponsored retirement plans.

FIRST TRUST MEGA CAP ALPHADEX(R) FUND--TOTAL RETURNS(1)

                                [GRAPHIC OMITTED]
                      [DATA POINTS REPRESENTED IN BAR CHART]

                     Calendar Year Total Returns as of 12/31

                              Year              %
                             ------         --------
                              2012            8.32%
                              2013           31.92%
                              2014            8.97%
                              2015           -0.26%

(1) The Fund's year-to-date return based on net asset value for the period
12/31/2015 to 3/31/2016 was -0.85%.





During the period shown in the chart above:

          BEST QUARTER                               WORST QUARTER
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      10.74% (March 31, 2012)                    -8.54% (June 30, 2012)
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The Fund's past performance (before and after taxes) is not necessarily an
indication of how the Fund will perform in the future.

AVERAGE ANNUAL TOTAL RETURNS FOR THE PERIODS ENDED DECEMBER 31, 2015



                                                                                                     SINCE INCEPTION
                                                                                         1 YEAR        (5/11/2011)
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Return Before Taxes                                                                      -0.26%          7.85%
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Return After Taxes on Distributions                                                      -0.97%          7.29%
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Return After Taxes on Distributions and Sale of Shares                                   -0.15%          5.89%
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S&P 100(R) Index
   (reflects no deduction for fees, expenses or taxes)                                    2.64%         12.12%
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Nasdaq AlphaDEX(R) Mega Cap Index
   (reflects no deduction for fees, expenses or taxes)                                     N.A.           N.A.
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Defined Mega Cap Index
   (reflects no deduction for fees, expenses or taxes)                                    0.56%          8.73%
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    * On April 8, 2016, the Fund's underlying index changed from the Defined
      Mega Cap Index to the Nasdaq AlphaDEX(R) Mega Cap Index. Because the
      Fund's new underlying index had an inception date of January 11, 2016,
      performance information is not included above. The new Index is
      substantially similar to the Defined Mega Cap Index.

MANAGEMENT

      INVESTMENT ADVISOR

      First Trust Advisors L.P. ("First Trust" or the "Advisor")

      PORTFOLIO MANAGERS

      The Fund's portfolio is managed by a team (the "Investment Committee")
      consisting of:

         o  Daniel J. Lindquist, Chairman of the Investment Committee and
            Managing Director of First Trust;

         o  Jon C. Erickson, Senior Vice President of First Trust;

         o  David G. McGarel, Chief Investment Officer and Managing Director of
            First Trust;

         o  Roger F. Testin, Senior Vice President of First Trust;

         o  Stan Ueland, Senior Vice President of First Trust; and

         o  Chris A. Peterson, Senior Vice President of First Trust.

      The Investment Committee members are primarily and jointly responsible for
      the day-to-day management of the Fund. Each Investment Committee member
      has served as a part of the portfolio management team of the Fund since
      2011, except for Chris A. Peterson, who has served as a member of the
      portfolio management team since 2016.

PURCHASE AND SALE OF FUND SHARES

The Fund issues and redeems shares on a continuous basis, at net asset value,
only in Creation Units consisting of 50,000 shares. The Fund's Creation Units
are generally issued and redeemed in-kind for securities in which the Fund
invests and, in certain circumstances, for cash, and only to and from
broker-dealers and large institutional investors that have entered into
participation agreements. Individual shares of the Fund may only be purchased
and sold on Nasdaq through a broker-dealer. Shares of the Fund trade on Nasdaq
at market prices rather than net asset value, which may cause the shares to
trade at a price greater than net asset value (premium) or less than net asset
value (discount).

TAX INFORMATION

The Fund's distributions are taxable and will generally be taxed as ordinary
income or capital gains. Distributions on shares held in a tax deferred account,
while not immediately taxable, will be subject to tax when the shares are no
longer held in a tax deferred account.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

If you purchase shares of 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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