SUMMARY PROSPECTUS

April 29, 2020 (As Amended August 27, 2020)

MFS^® Total Return Series

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 fund’s reports to shareholders and statement of additional information, online at insurancefunds.mfs.com.  You can also get this information at no cost by calling 1-800-225-2606 or by sending an e-mail request to orderliterature@mfs.com.  The fund’s prospectus and statement of additional information, both dated April 29, 2020, as may be amended or supplemented from time to time, are incorporated by reference into this summary prospectus.

CLASS	TICKER SYMBOL
Initial Class	N/A
Service Class	N/A

Beginning on January 1, 2021, as permitted by regulations adopted by the U.S. Securities and Exchange Commission, the insurance company that offers your contract may determine that it will no longer send you paper copies of the fund's annual and semiannual shareholder reports unless you specifically request paper copies from the insurance company or from your financial intermediary.  Instead, the shareholder reports will be made available on a Web site (insurancefunds.mfs.com or other Web site of which you will be notified), and the insurance company will notify you by mail each time a report is posted and provide you with a Web site link to access the report.  Instructions for requesting paper copies will be provided by your insurance company or financial intermediary.

If you already elected to receive shareholder reports by email, you will not be affected by this change and you need not take any action.  If your insurance company or financial intermediary offers electronic delivery, you may elect to receive shareholder reports and other communications from the insurance company or financial intermediary by email by following the instructions provided by the insurance company or financial intermediary.

Beginning on January 1, 2019, you may elect to receive all future reports in paper free of charge from the insurance company or financial intermediary.  You can inform the insurance company or financial intermediary that you wish to continue receiving paper copies of your shareholder reports by contacting your insurance company or financial intermediary.  Your election to receive reports in paper will apply to all funds held in your account with your insurance company or financial intermediary.

Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return.

Fees and Expenses

This table describes the fees and expenses that you may pay when you hold shares of the fund.  If the fees and expenses imposed by the insurance company that issued your variable contracts or other eligible investor through which the fund is offered were included, your expenses would be higher.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
		Initial Class	Service Class
	Management Fee	0.67%	0.67%
	Distribution and/or Service (12b-1) Fees	None	0.25%
	Other Expenses	0.03%	0.03%
	Total Annual Fund Operating Expenses	0.70%	0.95%
	Fee Reductions and/or Expense Reimbursements1	(0.09)%	(0.09)%
	Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	0.61%	0.86%

1 Massachusetts Financial Services Company has agreed in writing to bear the fund’s expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that “Total Annual Fund Operating Expenses” do not exceed 0.61% of the class' average daily net assets annually for Initial Class shares and 0.86% of the class' average daily net assets annually for Service Class shares. This written agreement will continue until modified by the fund’s Board of Trustees, but such agreement will continue until at least April 30, 2021.

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MFS Total Return Series

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. If the fees and expenses imposed by the insurance company that issued your variable contracts or other eligible investor through which an investment in the fund is made were included, your expenses would be higher.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods; your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

	1 YEAR	3 YEARS	5 YEARS	10 YEARS
Initial Class Shares	$62	$215	$381	$862
Service Class Shares	$88	$294	$517	$1,158

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. These transaction 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 42% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund's investment adviser) invests the fund’s assets in equity securities and debt instruments. Equity securities include common stocks and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer. Debt instruments include corporate bonds, U.S. Government securities, securitized instruments, and other obligations to repay money borrowed. MFS generally invests approximately 60% of the fund’s assets in equity securities and approximately 40% of the fund's assets in debt instruments. These weightings do not reflect the fund's cash balance and can vary over time due to market movements and cash flows.

Of the fund's investments in equity securities, MFS focuses on investing the fund's assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies).

MFS normally invests a portion of the fund’s assets in income-producing equity securities.

While MFS may invest the equity portion of the fund’s assets in securities of companies of any size, MFS primarily invests in securities of companies with large capitalizations.

Of the fund’s investments in debt instruments, MFS generally invests substantially all of these investments in investment grade quality debt instruments.

MFS may purchase or sell securities for the fund on a when-issued, delayed delivery, or forward commitment basis.

MFS may invest the fund’s assets in foreign securities.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and instruments. Quantitative models that systematically evaluate issuers and instruments are used by certain of the fund's equity securities portfolio managers and may also be considered by the fund's other portfolio managers.

Beginning December 31, 2019, in connection with the pending portfolio management changes described under the sub-section entitled "Portfolio Manager(s)," the portion of the fund for which equity securities are selected primarily based on blending fundamental and quantitative research will be transitioned over time to a strategy of selecting investments primarily based on fundamental analysis of individual issuers.  It is expected that the transition will be completed by December 31, 2020.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Investment Selection Risk: MFS' investment analysis, its development and use of quantitative models, and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. The quantitative models used by MFS (both proprietary and third-party) may not produce the intended results for a variety of reasons, including the factors used in the models, the weight placed on each factor in the models, changing sources of market return or market risk, and technical issues in the design, development, implementation, application, and maintenance of the models (e.g., incomplete or inaccurate data, programming or other software issues, coding errors, and technology failures).

Equity Market Risk/Company Risk:  Equity markets are volatile and can decline significantly in response to, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.  These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general.  Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market.

Value Company Risk: The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general.

Debt Market Risk:  Debt markets can be volatile and can decline significantly in response to, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.  These conditions can affect a single instrument, issuer, or borrower, a particular type of instrument, issuer, or borrower, a segment of the debt markets or the debt markets generally. Certain events can have a dramatic adverse effect on debt markets and may lead to periods of high volatility and reduced liquidity in a debt market or segment of a debt market.

Interest Rate Risk: In general, the price of a debt instrument falls when interest rates rise and rises when interest rates fall. Interest rate risk is generally greater for instruments with longer maturities, or that do not pay current interest.

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MFS Total Return Series

Credit Risk: The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or other entity responsible for payment, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in, or perceptions of, the financial condition of the issuer, borrower, counterparty, or other entity, or underlying collateral or assets, or changes in, or perceptions of, specific or general market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.

Foreign Risk: Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to emerging and frontier markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

Prepayment/Extension Risk: Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Focus Risk:  Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund's performance will be affected by the conditions in the industries, sectors, countries and regions to which the fund is exposed.

Leveraging Risk: Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Counterparty and Third Party Risk: Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability or willingness to perform in accordance with the terms of the transaction.

Liquidity Risk: It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares.  These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices.  Redemptions of a large number of shares also may increase transaction costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund's performance over time compares with that of a broad measure of market performance and one or more other measures of performance for markets in which the fund may invest.

The fund’s past performance does not necessarily indicate how the fund will perform in the future. Updated performance is available at mfs.com or by calling 1-877-411-3325. If the fees and expenses imposed by the insurance company that issued your variable contracts or other eligible investor through which an investment in the fund is made were included, they would reduce the returns shown.

Initial Class Bar Chart.

The total return for the three-month period ended March 31, 2020, was (14.26)%. During the period(s) shown in the bar chart, the highest quarterly return was 8.77% (for the calendar quarter ended March 31, 2019) and the lowest quarterly return was (8.84)% (for the calendar quarter ended September 30, 2011).

Performance Table.

Average Annual Total Returns

(For the Periods Ended December 31, 2019)

	1 YEAR	5 YEARS	10 YEARS
Initial Class Shares	20.38%	6.76%	8.35%
Service Class Shares	20.12%	6.50%	8.08%
Index Comparisons (Reflects no deduction for fees, expenses, or taxes)
Standard & Poor's 500 Stock Index	31.49%	11.70%	13.56%
MFS Total Return Blended Index	22.18%	8.37%	9.77%
Bloomberg Barclays U.S. Aggregate Bond Index	8.72%	3.05%	3.75%

As of December 31, 2019, the MFS Total Return Blended Index (the Blended Index) consisted of the following indices and weightings: 60% Standard & Poor's 500 Stock Index and 40% Bloomberg Barclays U.S. Aggregate Bond Index. The components and weightings of the Blended Index may have differed during the periods, and may differ in the future.

Investment Adviser

MFS serves as the investment adviser for the fund.

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MFS Total Return Series

Portfolio Manager(s)

Portfolio Manager	Since	Title
Brooks Taylor	2004	Investment Officer of MFS
Steven Gorham	2002	Investment Officer of MFS
Alexander Mackey	December 2019	Investment Officer of MFS
Joshua Marston	2008	Investment Officer of MFS
Johnathan Munko	December 2019	Investment Officer of MFS
Henry Peabody	December 2019	Investment Officer of MFS
Robert Persons	2017	Investment Officer of MFS
Jonathan Sage	2013	Investment Officer of MFS

Effective December 31, 2020, Brooks Taylor and Jonathan Sage will no longer be portfolio managers of the fund. Effective June 30, 2021, Robert Persons will no longer be a portfolio manager of the fund.

Purchase and Sale of Fund Shares

You should consult with the insurance company that issued your variable contract, or other eligible investor through which your investment in the fund is made, for minimum investment requirements and redemption procedures.

Taxes

You should consult with the insurance company that issued your variable contract, or other eligible investor through which your investment in the fund is made, to understand the tax treatment of your investment.

Payments to Financial Intermediaries

The fund, MFS, and/or its affiliates may make payments to insurance companies, other financial intermediaries, and all of their affiliates, for distribution and/or other services. These payments may create a conflict of interest for the insurance company or other financial intermediary to include the fund as an investment option in its product or to recommend the fund over another investment option. Ask your financial intermediary or insurance company, or visit your financial intermediary's or insurance company's Web site, for more information.

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