<PAGE>   1
                                                                   EXHIBIT 10.66


                            FIRST AMENDMENT TO LEASE
                            ------------------------

     This First Amendment to Lease (the "First Amendment") is dated as of the
31st day of January, 1994 by and between John A. Pirovano, William A. Halsey and
Stanton H. Zarrow, as TRUSTEES OF 60 STATE STREET TRUST under Declaration of
Trust dated September 10, 1970 and recorded with the Suffolk County Registry of
Deeds in Book 8389, Page 286, as amended (the "Landlord") and THE PIONEER GROUP,
INC. ("Tenant").

                                    RECITALS
                                    --------

     WHEREAS, Landlord and Tenant entered into a lease dated as of July 3, 1991
(the "Lease") for certain space ("Premises") in the building commonly known as
60 State Street, Boston, Massachusetts (the "Building"); and

     WHEREAS, Landlord and Tenant desire to amend the Lease to include within
the Premises all of Floor 19 of the Building consisting of approximately 21,698
rentable square feet of space, shown as the "F1oor 19 Premises" on the floor
plan attached hereto as AMENDMENT TO EXHIBIT A-1 and incorporated herein, and to
amend certain terms and conditions of the Lease as described below.

                                    AGREEMENT
                                    ---------

     NOW, THEREFORE, in consideration of Ten Dollars ($10.00) and other good and
valuable consideration, the receipt and sufficiency of which are acknowledged
and agreed, Landlord and Tenant hereby agree that Landlord shall lease to
Tenant, and Tenant shall lease fromm Landlord, the Floor 19 Premises on the
following terms and conditions:

     1.   TERM. The Term for the Floor 19 Premises shall commence on July 1,
          1994 and shall expire on March 31, 2007, unless earlier terminated as
          set forth in Amendment Section 6 or extended pursuant to the Lease.
          Tenant acknowledges that the Term for the Floor 19 Premises shall
          continue notwithstanding any election by Tenant not to renew the
          initial Term of the Lease for all or a portion of the remainder of
          Tenant's Premises which initial Term expires on March 31, 2002.
          Landlord and Tenant further acknowledge that the Floor 19 Premises
          shall be deemed Additional Space provided that Tenant's rights to
          extend the Term for the Floor 19 Premises shall be subject to the
          rights of Hale and Dorr pursuant to the Hale and Dorr Lease, as
          amended. The Floor 19 Premises shall not be deemed to be Substitute
          Option Space pursuant to Section 2.1.3(a).

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     2.   ANNUAL FIXED RENT FOR INITIAL TERM AND ADDITIONAL RENT. Annual Fixed
          Rent for the Floor 19 Premises shall be as follows:

          (i)  For the period from July 1, 1994 through December 31, 1994,
               Tenant shall not be required to pay any Annual Fixed Rent for the
               Floor 19 Premises.

          (ii) From January 1, 1995 through December 31, 1998, the Annual Fixed
               Rent for the Floor 19 Premises shall be $8.50 per rentable square
               foot ($184,433.00 per annum; $15,369.42 per month).

         (iii) From January 1, 1999 through December 31, 2002, the Annual Fixed
               Rent for the Floor 19 Premises shall be $10.50 per rentable
               square foot ($227,829.00 per annum; $18,985.75 per month).

         (iii) From January 1, 2003 through March 31, 2007, Annual Fixed Rent
               for the Floor 19 Premises shall be $12.50 per rentable square
               foot ($271,225.00 per annum; $22,602.08 per month).

          Tenant shall pay additional rent for the Floor 19 Premises on the same
          terms and conditions as provided in the Lease for the initial Premises
          provided that, for the period from July 1, 1994 through December 31,
          1994, Tenant shall not be required to pay Operating Expenses Allocable
          to the Floor 19 Premises or Landlord's Tax Expenses Allocable to the
          Floor 19 Premises.

     3.   LANDLORD'S WORK ON THE FLOOR 19 PREMISES. Notwithstanding any
          provisions of the Lease to the contrary including, without
          limitation, Sections 3.1 and 3.6, Landlord's Work with respect to
          the Floor 19 Premises shall be solely as set forth on AMENDMENT
          EXHIBIT B-1 and except for Landlord's Work, the Floor 19 Premises
          shall be delivered to Tenant broom-clean and in their then "as is"
          condition. Landlord shall perform Landlord's Work, at Landlord's sole
          cost and expense, and shall use reasonable efforts to substantially
          complete Landlord's Work and to deliver the Floor 19 Premises to
          Tenant by July 1, 1994.

     4.   TENANT'S WORK ON THE FLOOR 19 PREMISES. Commencing on July 1, 1994,
          Tenant shall have the right to construct improvements to the Floor 19
          Premises subject to Landlord's approval of Tenant's plans and
          specifications, which approval shall not be unreasonably withheld or
          delayed, and subject to the other terms and conditions



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          of the Lease including Section 3.5. All Tenant improvements to the
          Floor 19 Premises shall be performed at Tenant's sole cost and
          expense, and Landlord shall not be obligated to reimburse or otherwise
          compensate Tenant for such improvements.

     5.   PARKING. Pursuant to Section 2.2.1 of the Lease, Tenant shall have the
          right to occupy seven (7) additional parking spaces in the Building
          garage and Tenant shall pay therefor the amounts calculated in
          accordance with Section 2.5.

     6.   LANDLORD'S RECAPTURE OF FLOOR 19. The Hale and Dorr Lease provides in
          Section 2.1.3 thereof that Hale and Dorr has the right and option to
          occupy Floor 19 as of April 1, 2005. If Hale and Dorr exercises its
          rights under the Hale and Dorr Lease with respect to the Floor 19
          Premises, then the following shall apply:

          (i)  Landlord shall notify Tenant on or before May 1, 2004 if Hale and
               Dorr exercises its right to lease Floor 19 ("Landlord's Floor 19
               Notice").

          (ii) The Lease will terminate with respect to the Floor 19 Premises
               only as of March 31, 2005 and Tenant shall surrender the Floor 19
               Premises to Landlord on or before that date in accordance with
               the terms of the Lease. Landlord and Tenant expressly acknowledge
               that, except for the Floor 19 Premises, the Lease will remain in
               full force and effect with respect to the entire Premises then
               being covered by the Lease, if any.

         (iii) For the period from October 1, 2004 through March 31, 2005,
               Tenant's obligation to pay Base Rent for the Floor 19 Premises
               and Operating Expenses Allocable to the Floor 19 Premises and
               Landlord's Tax Expenses Allocable to the Floor 19 Premises shall
               be waived.

          (iv) Notwithstanding any provisions of the Lease, as amended hereby,
               to the contrary, Landlord's Floor 19 Notice shall be deemed to be
               Landlord's Offer of Floor 16, pursuant to Section 2.1.4(b),
               except that: (a) Landlord shall not be required to include an
               estimate of 90% of FRV. The Annual Fixed Rent for Floor 16 for
               the period of April 1, 2005 through March 31, 2007 shall be at
               the rate of $12.50 per rentable square foot ($280,087.50 per
               annum based on 22,407 rentable


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               square feet); (b) the Annual Fixed Rent for Floor 16 for the
               period of October 1, 2004 through March 31, 2005 shall be abated
               fully; and (c) Landlord shall complete the improvements specified
               in Amendment Exhibit B-2.

          7.   ADJUSTMENT OF DATES. Notwithstanding any provision of this First
               Amendment to the contrary, if Landlord fails to substantially
               complete Landlord's Work and to deliver either the Floor 19
               Premises or Floor 16, as the case may be, to Tenant on the
               applicable date set forth above, Landlord shall not be liable for
               any damages caused thereby nor shall this First Amendment or the
               Lease be void or voidable, but the specified dates for (a) the
               commencement of the Term for the applicable space, (b) Tenant's
               right to commence work on or to use the applicable space, and (c)
               the commencement of Tenant's obligation to pay Base Rent for the
               applicable space, Operating Expenses Allocable to the applicable
               space and Landlord's Tax Expenses Allocable to the applicable
               space shall be adjusted by one (1) day for each day of delay, and
               all other dates shall remain as specified in this First Amendment
               provided that the dates described in clause (c) above shall not
               be so adjusted if Landlord's failure to substantially complete
               Landlord's Work or to deliver the applicable space is a result of
               the acts or omissions of Tenant. As an example, if Landlord is
               unable to deliver the Floor 19 Premises as required by this First
               Amendment until July 15, 1994, then the Term of the Lease for the
               Floor 19 Premises, and Tenant's right to commence work on and to
               use the Floor 19 Premises, shall commence on July 15, 1994, and,
               provided Landlord's failure to substantially complete Landlord's
               Work or to deliver the applicable space is not a result of the
               acts or omissions of Tenant, then Tenant shall not be required to
               pay Annual Fixed Rent, Operating Expenses Allocable to the Floor
               19 Premises or Landlord's Tax Expenses Allocable to the Floor 19
               Premises for the period of July 15, 1994 through January 14,
               1995, but all other dates with respect to the Floor 19 Premises
               including, without limitation, the date on which Tenant is
               required to surrender the Floor 19 Premises (March 31, 2005 or
               March 31, 2007, as the case may be) shall remain the same.

          8.   WAIVERS AND SUBORDINATION OF CERTAIN RIGHTS. Notwithstanding
               any provision of the Lease to the contrary including, without
               limitation, Sections 2.1.3(a), 2.1.4 and 2.1.5, Tenant hereby (a)
               consents to ITT Sheraton's lease of Floors 13, 14, 15 and 16
               through September 30, 2004; (b) subordinates its rights with
               respect to Floors 13, 14 and 15 to the right to extend


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               the term of the ITT Sheraton Lease, as amended, through December
               31, 2008; and (c) subordinates its rights with respect to the
               space on Floor 9 now occupied by Lourie & Cutler together with up
               to an additional approximately 2,000 square feet of contiguous
               space for the continuing occupancy of Lourie & Cutler. In
               addition, Tenant hereby acknowledges that Landlord has used
               diligent efforts to gain control of the Sheraton Space and the
               initial L&C Space pursuant to Section 2.1.3(a) of the Lease.

          9.   LANDLORD'S WORK FLOORS 13, 14 AND 15. In the event Tenant leases
               any of Floors 13, 14 or 15 pursuant to Section 2.1.4, then
               Landlord's work on such Floors shall consist of the work
               described in Section 2.1.3(c) and only those sections of Exhibit
               E/F to the Lease that are set forth in Items 7 through 10 of
               AMENDMENT EXHIBIT B-l, and neither the time frames nor the
               penalties associated with the applicable sections of Exhibit E/F
               shall be applicable.

          10.  CAPITALIZED TERMS. Capitalized terms used herein but not defined
               shall have the meanings ascribed to them in the Lease.

          11.  RATIFICATION. Except as amended hereby, the terms and conditions
               of the Lease shall remain unaffected and the Lease shall remain
               in full force and effect.

                                             LANDLORD: TRUSTEES OF 60 STATE
                                               STREET TRUST

                                             By: /s/ John A. Pirovano
                                                --------------------------------
                                                John A. Pirovano, as Trustee
                                                of 60 State Street Trust,
                                                for self and Co-Trustee,
                                                but not individually



                                             TENANT: THE PIONEER GROUP, INC.

                                             By:/s/ John F. Cogan
                                                --------------------------------
                                                John F. Cogan, its President
                                                hereunto duly authorized



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                             AMENDMENT EXHIBIT A-1

                                Floor 19 Premises
                                -----------------



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                              AMENDMENT EXHIBIT B-1

                      Landlord's Work on Floor 19 Premises
                      ------------------------------------

     Landlord's Work for the Floor 19 Premises shall consist solely of the
following:

     1.   Demolish the existing improvements from slab to the slab including
          removal of improvements above the ceiling, provided that Landlord may
          leave in place all or any portion of the sprinkler distribution
          system, exit lighting and other improvements which may be required to
          maintain the space in compliance with applicable safety codes and
          insurance requirements, or as may be required to prevent damage to the
          Building;

     2.   Repair the core walls, patch and prime;

     3.   Repair any damage caused during demolition or construction of
          Landlord's Work;

     4.   Remove the connecting stair to the 20th floor and repair the slab;

     5.   Install an ADA compliant unisex restroom in a location to be selected
          by Tenant and using finishes comparable to the finishes in the unisex
          restrooms in Tenant's existing Premises provided that, notwithstanding
          any provision of this First Amendment to the contrary, Landlord shall
          not be required to have the unisex restroom substantially complete
          until the later of (a) July 1, 1994 or (b) ninety (90) days after
          Tenant delivers to Landlord notice of the designated location for the
          unisex restroom. If the ninety (90) day period has not lapsed and
          Landlord's Work other than the unisex restroom is substantially
          complete, Landlord shall be entitled to deliver possession of the
          Premises to Tenant and the date of such delivery shall be used for the
          purpose of determining the commencement date for the Floor 19
          Premises. In addition, at any time prior to Tenant giving Landlord
          notice of the location for the unisex restroom, Tenant may notify
          Landlord in writing of Tenant's election to install the unisex
          restroom. If Tenant so elects the installation of the unisex restroom
          shall no longer be part of Landlord's Work and Landlord shall
          reimburse Tenant for up to Fifteen Thousand Dollars ($15,000.00) of
          the cost of installing the unisex restroom using finishes comparable
          to the finishes in the unisex restrooms in Tenant's existing Premises.
          Landlord's reimbursement shall be made within thirty (30) days of
          Tenant's delivery to Landlord of paid invoices, lien waivers, and such
          other documentation as Landlord may reasonably require;



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     6.   Install electrical panels on Floor 19 to permit Tenant to connect its
          life-safety devices as required by applicable Building codes and the
          ADA;

     7.   Furnish and install a balancing device on Floor 19 to ensure that the
          Landlord provides 0.15 cfm of fresh air per rentable square foot;

     8.   Provide sufficient cooling capacity for the Floor 19 Premises
          including, without limitation, the following auxiliary areas: computer
          rooms, telephone equipment rooms, conference rooms, special use rooms,
          copy centers, word processing areas and mailrooms, as shown on the
          plans submitted by Tenant and approved by Landlord, all as required
          pursuant to Exhibit J, Section II. Notwithstanding the foregoing or
          any other provision of the Lease or this First Amendment, Landlord
          shall not be required to provide additional cooling capacity should
          Tenant substantially change the configuration of the Floor 19
          Premises. Any modification to the existing floor fan units or the
          addition of supplemental fan coil units resulting from such a change
          of configuration and/or use shall be at Tenant's sole expense;

     9.   The restrooms in the Floor 19 Premises shall comply with operational
          standards reasonably satisfactory to Tenant and with all code
          requirements as of the date possession of the Floor 19 Premises is
          delivered to Tenant, including toilet exhaust. All plumbing fixtures
          and water, waste and vent systems shall be in good repair and shall be
          at least equal to operational standards of first-class downtown
          Boston office towers;

     10.  Provide electrical power to the Floor 19 Premises sufficient to
          comply with the provisions of Exhibit J, Section VI; and

     11.  If the Floor 19 Premises shall be damaged by fire or by any other
          cause, risk or reason prior to Landlord's delivery of the Floor 19
          Premises to Tenant, the provisions of Section 6.1 shall apply to
          such space as if such space were included within the Premises,
          notwithstanding the fact that Landlord shall not have delivered such
          space, except that, in addition to the work set forth above,
          Landlord's restoration obligation under Section 6.1 shall be limited
          to restoration of such space as shell space only, meaning without
          damage to the restrooms, core, exterior walls, floor slabs, steelwork,
          fireproofing, window frames, mullions or other structural elements
          of the Building or to the Building systems.

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     Except as specifically set forth above, all improvements to the Floor 19
Premises shall be made by and at the expense of Tenant, subject to Landlord's
approval which shall not be unreasonably withheld or delayed, and subject to the
other terms and conditions of the Lease including Section 3.5.



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                              AMENDMENT EXHIBIT B-2

                                  Improvements
                                  ------------

     If Tenarnt exercises its right to lease Floor 16 pursuant to Section
2.1  4(b) of the Lease, Landlord's Work on Floor 16 shall consist solely of the
following:

     1.   Install an ADA compliant unisex restroom in a location to be selected
          by Tenant and using finishes comparable to the finishes in the unisex
          restrooms in Tenant's existing Premises provided that, notwithstanding
          any provision of this First Amendment to the contrary, Landlord shall
          not be required to have the unisex restroom substantially complete
          until the later of (a) October 1, 2004 or (b) ninety (90) days after
          Tenant delivers to Landlord notice of the designated location for the
          unisex restroom. If the ninety (90) day period has not lapsed and
          Landlord's Work other than the unisex restroom is substantially
          complete, Landlord shall be entitled to deliver possession of the
          Premises to Tenant and the date of such delivery shall be used for the
          purpose of determining the commencement date for Floor 16. In
          addition, at any time prior to Tenant giving Landlord notice of the
          location for the unisex restroom, Tenant may notify Landlord in
          writing of Tenant's election to install the unisex restroom. If Tenant
          so elects the installation of the unisex restroom shall no longer be
          part of Landlord's Work and Landlord shall reimburse Tenant for up to
          Fifteen Thousand Dollars ($15,000.00) of the cost of installing the
          unisex restroom using finishes comparable to the finishes in the
          unisex restrooms in Tenant's existing Premises. Landlord's
          reimbursement shall be made within thirty (30) days of Tenant's
          delivery to Landlord of paid invoices, lien waivers, and such other
          documentation as Landlord may reasonably require;

     2.   Install electrical panels on Floor 16 to permit Tenant to connect its
          life-safety devices as required by applicable Building codes and the
          ADA;

     3.   Furnish and install a balancing device on Floor 16 to ensure that the
          Landlord provides 0.15 cfm of fresh air per rentable square foot;

     4.   Provide sufficient cooling capacity for Floor 16 including, without
          limitation, the following auxiliary areas: computer rooms, telephone
          equipment rooms, conference rooms, special use rooms, copy centers,
          word processing areas and mailrooms, as shown on the plans submitted
          by

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          Tenant and approved by Landlord, all as required pursuant to Exhibit
          J, Section II. Notwithstanding the foregoing or any other provision of
          the Lease or this First Amendment, Landlord shall not be required to
          provide additional cooling capacity should Tenant substantially change
          the configuration and/or use of Floor 16. Any modification to the
          existing floor fan units or the addition of supplemental fan coil
          units shall be at Tenant's sole expense;

     5.   The restrooms in Floor 16 shall comply with operational standards
          reasonably satisfactory to Tenant and with all code requirements as of
          the date possession of Floor 16 is delivered to Tenant, including
          toilet exhaust. All plumbing fixtures and water, waste and vent
          systems shall be in good repair and shall be at least equal to
          operational standards of first-class downtown Boston office towers;

     6.   Provide electrical power to Floor 16 sufficient to comply with the
          provisions of Exhibit J, Section VI;

     7.   Landlord shall not be obligated to, but at its option, may remove any
          then existing improvements in such space, in which event
          Landlord shall repair any damages caused by such removal (unless the
          repair would be rendered unnecessary by Tenant's immediate intended
          use of such space), leaving such space without damage to the
          restrooms, core, exterior walls, floor slabs, steelwork, fireproofing,
          window frames, mullions or other structural elements of the Building
          or to the Building systems; and

     8.   If Floor 16 shall be damaged by fire or by any other cause, risk or
          reason prior to Landlord's delivery of Floor 16 to Tenant, the
          provisions of Section 6.1 shall apply to such space as if such space
          were included within the Premises, notwithstanding the fact that
          Landlord shall not have delivered such space, except that, in addition
          to the work set forth above, Landlord's restoration obligation under
          Section 6.1 shall be limited to restoration of such space as shelf
          space only, meaning without damage to the restrooms, core, exterior
          walls, floor slabs, steelwork, fireproofing, window frames, mullions
          or other structural elements of the Building or to the Building
          systems.

     Except as specifically set forth above, all improvements to Floor 16 shall
be made by and at the expense of Tenant, subject to Landlord's approval which
shall not be unreasonably withheld or delayed, and subject to the other terms
and conditions of the Lease including Section 3.5.

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<PAGE>   12




                               CONSENT OF LENDERS
                               ------------------

     The undersigned hereby acknowledge notice of the First Amendment to Lease
between Trustees of 60 State Street Trust and The Pioneer Group, Inc. dated
January 31, 1994 and consent thereto.



                                             TRUST COMPANY OF THE WEST, a
                                             California corporation, as trustee
                                             for TCW REALTY FUND VA, as tenant
                                             in common

                                             By: /s/
                                                --------------------------------
                                                Authorized signatory


                                             By: /s/
                                                --------------------------------
                                                Authorized signatory




                                             TCW REALTY FUND VB, a California
                                             limited partnership, as tenant in
                                             common

                                             By: TCW ASSET MANAGEMENT COMPANY,
                                                 a California corporation, as
                                                 General Partner

                                                By: /s/
                                                   -----------------------------
                                                   Authorized signatory


                                                By: /s/
                                                   -----------------------------
                                                   Authorized signatory




                                             By: WESTMARK REAL ESTATE INVESTMENT
                                                 SERVICES, a California general
                                                 partnership, as General Partner

                                                By: /s/
                                                   -----------------------------
                                                   Authorized signatory


                                                By: /s/
                                                   -----------------------------
                                                   Authorized signatory


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<PAGE>   13



                               CONSENT OF LENDERS
                               ------------------

     The undersigned hereby acknowledge notice of the First Amendment to Lease
between Trustees of 60 State Street Trust and The Pioneer Group, Inc. dated
January  , 1994 and consent thereto.

                                             TEACHERS INSURANCE ANNUITY
                                               ASSOCIATION OF AMERICA

                                             By:  /s/
                                                --------------------------------
                                                its
                                                hereunto duly authorized





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