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                                                                   EXHIBIT 10.75


                            SIXTH AMENDMENT TO LEASE


        This SIXTH AMENDMENT TO LEASE ("SIXTH AMENDMENT") is made as of October
5, 1998 by and between the TRUSTEES OF 60 STATE STREET TRUST under Declaration
of Trust dated September 10, 1970, recorded with Suffolk Deeds, Book 8389, Page
286, as amended, with an address of c/o Hines, 60 State Street, Boston,
Massachusetts 02109 ("LANDLORD"), and THE PIONEER GROUP, INC., having a mailing
address of 60 State Street, Boston, Massachusetts 02109 ("TENANT").

                                    RECITALS

        WHEREAS, Landlord and Tenant entered into a lease dated as of July 3,
1991, as amended by a certain First Amendment to Lease dated as of January 31,
1994, as further amended by a certain Second Amendment to Lease dated September
30, 1996, as further amended by a certain Third Amendment to Lease dated
November 15, 1996, as further amended by a certain Fourth Amendment to Lease
dated September __, 1997, and as further amended by a certain Fifth Amendment to
Lease dated as of December 31, 1997 (collectively, the "LEASE"), for certain
space ("Premises") on the 3rd, 4th, 5th, 6th, 14th, 17th, 18th and 19th floors
of the building commonly known as 60 State Street, Boston, Massachusetts (the
"BUILDING") (all capitalized terms not otherwise defined in this Sixth Amendment
shall have the meaning set forth in the Lease);

        WHEREAS, Landlord and Tenant desire to amend the Lease (i) to remove
approximately 15,287 rentable square feet of space on Floor 6 of the Building
known as the "REMAINING FLOOR 6 PREMISES" from the Premises effective as of
November 1, 1998, (ii) to remove approximately 7,120 square feet of space on
Floor 6 of the Building known as the "FLOOR 6 PREMISES" from the Premises
effective as of August 1, 1999, (iii) to include the entire 16th Floor of the
Building ("FLOOR 16 PREMISES") within the Premises effective as of September 1,
1998, (iv) to include the entire 15th Floor of the Building ("FLOOR 15
PREMISES") within the Premises effective as of April 1, 1999, and (v) to amend
certain terms and conditions of the Lease as described below;

        WHEREAS, Hale and Dorr LLP ("H&D") has by Seventh Amendment to Lease
executed currently herewith ("H&D SEVENTH AMENDMENT") (i) declined to exercise
its superior rights of first offer and refusal with respect to the Floor 15
Premises in connection with a certain offer letter from Landlord to H&D dated
August 18, 1998, as same has been extended, and (ii) agreed to lease a portion
of the Floor 6 Premises following Tenant's vacancy thereof and a portion of the
Remaining Floor 6 Premises effective as of August 1, 1999;

        WHEREAS, Adams, Harkness and Hill, Inc. ("AH&H") has by that certain
Second Amendment to Lease by and between AH&H and Landlord to be executed
concurrently herewith ("AH&H SECOND AMENDMENT") agreed to lease the Remaining
Floor 6 Premises effective as of November 1, 1998;


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        WHEREAS, Citizens Financial Group, Inc. (successor-in-interest to Bank
of Ireland First Holdings, Inc. ("BANK OF IRELAND")) has by Lease Termination
Agreement executed currently herewith ("LEASE TERMINATION Agreement") agreed to
terminate that certain Lease dated June 15, 1994, as amended, by and between
Bank of Ireland and Landlord with respect to approximately 4,045 square feet of
space on the 20th Floor of the Building ("20TH FLOOR SPACE"), as amended
("CITIZENS LEASE"), effective as of March 31, 1999; and

        WHEREAS, Tenant and AH&H have acknowledged that the termination of the
Citizens Lease shall automatically terminate that certain Sublease dated as of
August 15, 1996 by and between Citizens and Tenant ("PIONEER Sublease") and that
certain temporary license agreement between Tenant and AH&H ("AH&H LICENSE")
with respect to the 20th Floor Space.

                                    AGREEMENT

        NOW, THEREFORE, in consideration of Ten Dollars ($10.00) and other good
and valuable consideration, the receipt and sufficiency of which hereby are
acknowledged and agreed, Landlord and Tenant hereby agree as follows:

        1.      RECITALS. The foregoing recitals are hereby incorporated by
                reference.

        2.      LEASE OF FLOOR 6 PREMISES. Notwithstanding anything to the
                contrary set forth in the Lease, including without limitation
                the provisions of the Fifth Amendment to Lease, the term with
                respect to the Floor 6 Premises shall expire on July 31, 1999.
                Tenant hereby acknowledges and agrees that the Remaining Floor 6
                Premises shall not become part of the Premises and shall,
                instead, be leased, in part, to AH&H pursuant to the AH&H Second
                Amendment, and, in part, to H&D pursuant to the H&D Seventh
                Amendment. On or before July 31, 1999, Tenant shall surrender
                the Floor 6 Premises to Landlord in accordance with the
                requirements of Section 5.2 of the Lease. Pursuant to Section
                2.1.3(b) of the Lease, because Tenant has (i) accepted
                Landlord's right of first offer to lease the Floor 16 Premises
                at the Annual Fixed Rent set forth in Section 2.5 of the Lease,
                and (ii) has not elected to terminate the Lease with respect to
                the Floor 6 Premises and the Remaining Floor 6 Premises (which
                were previously designated as "Substitute Option Space")
                effective as of September 1, 1998, the Annual Fixed Rent for the
                Floor 6 Premises shall be increased to 90% of Fair Rental Value,
                or $29.70 per rentable square foot, for the period from October
                5, 1998 through July 31, 1999 ($211,464.00 per year; $17,622.00
                per month), partial months to be prorated. Any underpayments
                made by Tenant with respect to the Annual Fixed Rent due to
                Landlord for the Floor 6 Premises shall be rectified with the
                next installment of Annual Fixed Rent due hereunder.

        3.      SUBSTITUTE OPTION SPACE. Landlord and Tenant acknowledge and
                agree that (i) Tenant shall have no further right to designate
                or relocate "Substitute Option Space" pursuant to Section
                2.1.3(b) of the Lease, and (ii) any future space offered to
                Ten-

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                ant anywhere in the Building pursuant to Section 2.1.4 of the
                Lease shall be offered at an Annual Fixed Rent of 90% of Fair
                Rental Value.

          4.    LEASE OF FLOOR 16 PREMISES. Landlord shall lease to Tenant, and
                Tenant shall lease from Landlord, the Floor 16 Premises for a
                term commencing on October 5, 1998 and ending on March 31, 2002.
                Annual Fixed Rent for the Floor 16 Premises shall be as follows:

                      (i) For the period from October 5, 1998 through March 31,
                1999, the Annual Fixed Rent for the Floor 16 Premises shall be
                $17.85 per rentable square foot;

                      (ii) For the period from April 1, 1999 through March 31,
                2000, the Annual Fixed Rent for the Floor 16 Premises shall be
                $18.85 per rentable square foot;

                      (iii) For the period from April 1, 2000 through March 31,
                2001, the Annual Fixed Rent for the Floor 16 Premises shall be
                $19.85 per rentable square foot; and

                      (iv) For the period from April 1, 2001 through March 31,
                2002, the Annual Fixed Rent for the Floor 16 Premises shall be
                $20.85 per rentable square foot.

                Tenant shall pay additional rent for the Floor 16 Premises on
                the same terms and conditions as provided in the Lease for the
                initial Premises. The Floor 16 Premises shall constitute
                Additional Space under the Lease.

          5.    LANDLORD'S WORK ON THE FLOOR 16 PREMISES. Notwithstanding any
                provisions of the Lease to the contrary including, without
                limitation, Sections 3.1 and 3.6, the Floor 16 Premises shall be
                delivered to Tenant broom-clean and in their then "AS IS"
                condition, and except for "Landlord's Work" identified on SIXTH
                AMENDMENT EXHIBIT B attached hereto and made a part hereof,
                Landlord shall have no obligation to make any improvements or
                repairs to the Floor 16 Premises. Tenant acknowledges that
                Landlord shall be performing Landlord's Work within the Floor 16
                Premises concurrently with Tenant's Work on the Floor 16
                Premises. Landlord and Tenant each agrees that it shall
                coordinate with the other in connection with the performance of
                such party's work in order to minimize any interference with the
                performance of the other party's work in the Floor 16 Premises.

          6.    TENANT'S WORK ON THE FLOOR 16 PREMISES. Commencing on October 5,
                1998, Tenant shall have the right to construct improvements to
                the Floor 16 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 of the Lease including Section 3.5. All Tenant
                improvements to the Floor 16 Premises shall be performed at
                Tenant's sole cost and expense, and Landlord shall 




                                       3



<PAGE>   4

                not be obligated to reimburse or otherwise compensate Tenant for
                such improvements.

          7.    LEASE OF FLOOR 15 PREMISES. (a) Landlord shall lease to Tenant,
                and Tenant shall lease from Landlord, the Floor 15 Premises for
                a term commencing on April 1, 1999 or the Delivery Date (defined
                below), if applicable, and ending on March 31, 2002 ("15TH FLOOR
                TERM"). Annual Fixed Rent for the Floor 15 Premises for the
                entire 15th Floor Term shall be $29.70 per rentable square foot
                ($665,487.90 per year; $55,457.33 per month). Tenant shall pay
                additional rent for the Floor 15 Premises on the same terms and
                conditions as provided in the Lease for the initial Premises.
                The Floor 15 Premises shall constitute Additional Space under
                the Lease.

                (b) In the event ITT Sheraton Corporation ("SHERATON") contacts
                Landlord to request an early termination of the Lease dated as
                of September 1, 1998 by between Landlord and Sheraton ("SHERATON
                LEASE") with respect to its occupancy of the Floor 15 Premises,
                Landlord shall notify Tenant in writing of such request and the
                proposed surrender date of the Floor 15 Premises by Sheraton
                ("PROPOSED FLOOR 15 SURRENDER DATE"). Tenant shall have ten (10)
                days from the date of Landlord's notice to notify Landlord in
                writing as to whether Tenant wishes to accept possession of the
                Floor 15 Premises on the day after the Proposed Floor 15
                Surrender Date ("DELIVERY Date"). If Tenant timely notifies
                Landlord of its intent to accept the Floor 15 Premises on the
                Delivery Date, Landlord shall enter into an amendment to the
                Sheraton Lease terminating the Lease with respect to the Floor
                15 Premises effective as of the Proposed Surrender Date.

                (c) In the event Sheraton shall fail to surrender the Floor 15
                Premises to Landlord as required under the Sheraton Lease, and
                Landlord shall thereafter fail to deliver the Floor 15 Premises
                on or before July 31, 1999, Tenant's obligation to surrender the
                Floor 6 Premises to Landlord by such date shall be extended one
                day for each day beyond such date Landlord fails to deliver the
                Floor 15 Premises

          8.    LANDLORD'S WORK ON THE FLOOR 15 PREMISES. Notwithstanding any
                provisions of the Lease to the contrary including, without
                limitation, Sections 3.1 and 3.6, the Floor 15 Premises shall be
                delivered to Tenant broom-clean and in their then "AS IS"
                condition, and except for "Landlord's Work" identified on SIXTH
                AMENDMENT EXHIBIT B attached hereto and made a part hereof,
                Landlord shall have no obligation to make any improvements or
                repairs to the Floor 15 Premises. Tenant acknowledges that
                Landlord shall be performing Landlord's Work within the Floor 15
                Premises concurrently with Tenant's Work on the Floor 15
                Premises. Landlord and Tenant each agrees that it shall
                coordinate with the other in connection with the performance of
                such party's work in order to minimize any interference with the
                performance of the other party's work in the Floor 15 Premises.

          9.    TENANT'S WORK ON THE FLOOR 15 PREMISES. Upon delivery of
                possession of the Floor 15 Premises, Tenant shall have the right
                to construct improvements to the Floor 15 

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                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 of the Lease including Section 3.5. All Tenant
                improvements to the Floor 15 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.

        10.     FLOOR 3 PREMISES. Notwithstanding anything to the contrary set
                forth in the Lease, Tenant shall not have the right to extend
                the Term with respect to the Floor 3 Premises beyond March 31,
                2002. On or before such date, Tenant shall surrender the Floor 3
                Premises to Landlord in the condition required under Section 5.2
                of the Lease.

        11.     RELEASE OF FLOOR 14 PREMISES.  The Fourth Amendment to Lease is 
                hereby deemed to be null and void.


        12.     PARKING SPACES. (a) FLOOR 6 PREMISES. Notwithstanding anything
                to the contrary set forth in the Lease, including without
                limitation the provisions of the Fifth Amendment to Lease,
                Tenant shall not be entitled to occupy any additional parking
                spaces in the Building garage in connection with the leasing of
                the Floor 6 Premises through July 31, 1999. Tenant shall retain
                its right set forth in the Second Amendment to Lease to occupy
                one (1) non-reserved parking space until July 31, 1999, at which
                time Tenant shall surrender said parking space.

                (b) FLOOR 16 PREMISES. Commencing on October 5, 1998, in
                connection with the leasing of the Floor 16 Premises, Tenant
                shall be entitled to occupy three (3) additional non-reserved
                parking spaces and four (4) additional reserved parking spaces
                in the Building garage at the rates set forth in Section 2.5 of
                the Lease. Tenant shall enter into separate parking agreements
                with the garage operator with respect to the foregoing
                additional parking spaces concurrently herewith.

                (c) FLOOR 15 PREMISES. Commencing on the earlier of the Delivery
                Date or April 1, 1999, in connection with the leasing of the
                Floor 15 Premises, Tenant shall be entitled to occupy three (3)
                additional unreserved parking spaces and four (4) additional
                reserved parking spaces in the Building garage at the current
                market rates charged by the parking garage operator. Tenant
                shall enter into separate parking agreements with the garage
                operator with respect to the foregoing additional parking spaces
                concurrently herewith.

                (d) FLOOR 3 PREMISES. In connection with the surrender of the
                Floor 3 Premises, Tenant shall surrender seven (7) unreserved
                parking spaces in the Building garage attributable to the
                leasing of the Floor 3 Premises to Landlord as of March 31,
                2002.



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<PAGE>   6

        13.     TERMINATION OF PIONEER SUBLEASE. Tenant acknowledges the
                termination of the Pioneer Sublease and the AH&H License
                effective as of March 31, 1999 as a result of the termination of
                the Citizens Lease pursuant to the Lease Termination Agreement.

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

        15.     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.

        16.     BINDING EFFECT. This Sixth Amendment shall have the effect of an
                agreement under seal and shall be binding upon and inure to the
                benefit of the parties hereto and their respective heirs,
                executors, administrators, successors and assigns.

        17.     CONTINGENCIES. Landlord's obligation to deliver possession of
                the Floor 15 Premises to Tenant on or before April 1, 1999 is
                specifically contingent upon the delivery of the Floor 15
                Premises from ITT Sheraton Corporation to Landlord on or before
                the earlier of the Delivery Date or March 31, 1999.

        18.     NO LIABILITY OF LANDLORD. Tenant expressly acknowledges and
                agrees that (i) this Sixth Amendment, the H&D Seventh Amendment,
                the AH&H Second Amendment, the Lease Termination Agreement, and
                the Sheraton Lease (collectively, the "TRANSACTIOn DOCUMENTS")
                have been executed as part of a larger transaction to
                redistribute space within the Building amongst Tenant, H&D, and
                AH&H in accordance with the terms of the Transaction Documents
                (collectively, the "Transaction"); (ii) the Transaction requires
                some of the tenants in the Building who are parties to the
                Transaction Documents (each an "OBLIGATED PARTY" and
                collectively, the "OBLIGATED PARTIES") to deliver certain
                premises or parking spaces to Landlord on or before dates
                certain identified in the Transaction Documents (collectively,
                the "DELIVERY OBLIGATIONS"), the performance of which is a
                precondition for some of the obligations of the parties under
                this Sixth Amendment; and (iii) Landlord has agreed to enter
                into the Transaction and execute the Transaction Documents in
                order to assist Tenant and the other Obligated Parties obtain
                desired space within the Building; provided Landlord will not
                incur any liability to Tenant for any failure by one or more of
                the Obligated Parties to perform its or their Delivery
                Obligations. Tenant hereby irrevocably and unconditionally
                releases Landlord and waives any and all claims which it may
                have against Landlord, however and whenever arising, whether in
                law or in equity, in connection with any failure by any of the
                Obligated Parties to perform its or their Delivery Obligations.
                Following full and complete performance by all Obligated Parties
                of their respective Delivery Obligations, this release and
                waiver shall be of no further force and effect.



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        19.     NO THIRD PARTY BENEFICIARIES. This Sixth Amendment shall not
                confer any rights to any parties other than Landlord and Tenant,
                and no third parties shall have the right to enforce the terms
                hereof.

        EXECUTED under seal as of the date first set forth above.

                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-Trustees
                                        but not individually

                TENANT:             THE PIONEER GROUP, INC.


                                    By: /s/ Stephen G. Kasnet

                                        its
                                        hereunto duly authorized




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                            SIXTH AMENDMENT EXHIBIT A

                PLANS OF FLOOR 16 PREMISES AND FLOOR 15 PREMISES
                              AND FLOOR 6 PREMISES





                      [Floor Plan Intentionally Omitted]







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                            SIXTH AMENDMENT EXHIBIT B

 LANDLORD'S WORK WITH RESPECT TO THE FLOOR 16 PREMISES AND THE FLOOR 15 PREMISES

1.       Install an ADA-compliant unisex rest room in a location to be selected
         by Tenant and approved by Landlord, such approval not to be
         unreasonably withheld; using finishes comparable to the finishes in the
         unisex rest room in Tenant's existing Premises.

2.       The rest rooms shall comply with operational standards reasonably
         satisfactory to Tenant and with all code requirements as of the date
         possession is delivered to Tenant, including toilet exhaust. All
         plumbing fixtures and water, waster, and vent systems shall be in good
         repair.

3.       Provide sufficient cooling capacity to the Floor 16 Premises and the
         Floor 15 Premises, as applicable, to comply with the provisions of
         Exhibit J, Section II. Notwithstanding the foregoing or any other
         provision of the Lease or this Sixth Amendment, Landlord shall not be
         required to provide additional cooling capacity to the Floor 16
         Premises and the Floor 15 Premises, as applicable, should Tenant
         substantially change the configuration and/or use of the Floor 16
         Premises and the Floor 15 Premises, as applicable, after Tenant's
         initial occupancy; 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 the Tenant's sole
         expense.

4.       Provide electrical power to the Floor 16 Premises and the Floor 15
         Premises, as applicable, sufficient to comply with the provisions of
         Exhibit J, Section VI and install electrical panels if necessary in the
         Floor 16 Premises and the Floor 15 Premises, as applicable, to permit
         Tenant to connect its lifesafety devices as required by applicable
         Building codes and the ADA.

5.       Adjust the height of the elevator wall buttons adjacent to the elevator
         doors within the Floor 15 Premises and the Floor 16 Premises, as
         applicable, in order to make the same comply with ADA requirements.

6.       Adjust the height and modify the water access mechanisms of the
         existing water bubbler(s) within the Floor 15 Premises and the Floor 16
         Premises, as applicable, in order to make the same comply with ADA
         requirements, or provide a new ADA-compliant water bubbler for the
         Floor 15 Premises and the Floor 16 Premises, as applicable, if no water
         bubbler currently exists on such floor(s).




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                               CONSENT OF LENDERS

        The undersigned hereby acknowledges notice of the Sixth Amendment to
Lease between the Trustees of 60 State Street Trust and The Pioneer Group, Inc.
dated as of October 5, 1998 and consents thereto.

                                    CORNERSTONE PROPERTIES, INC.


                                    By: /s/ Scott M. Dalrimple

                                        Its Vice President
                                        hereunto duly authorized





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<PAGE>   11


                               CONSENT OF LENDERS

        The undersigned hereby acknowledges notice of the Sixth Amendment to
Lease between the Trustees of 60 State Street Trust and The Pioneer Group, Inc.
dated as of October 5, 1998 and consents thereto.


                                    TEACHERS INSURANCE ANNUITY
                                    ASSOCIATION OF AMERICA


                                    By: /s/ Joan Herman

                                        its
                                        hereunto duly authorized





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