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                                                                   EXHIBIT 10.21

                                ADDENDUM TO LEASE

         I.       RECITALS

                  This Addendum to Lease (hereinafter "Addendum") is entered
         into by and between SIERRA EQUITIES, INC., a corporation (hereinafter
         "Landlord") and MESA GENERAL HOSPITAL, INC., an Arizona corporation
         (hereinafter "Tenant") for the purpose of amending and modifying that
         certain Lease dated July 29, 1977, whereby Landlord leased to Tenant
         certain premises located at 515 North Mesa Drive, Mesa, Arizona 85201
         (hereinafter "Lease"). For good and valuable consideration, receipt of
         which is hereby acknowledged the parties hereto agree as follows:

         II.      MODIFICATIONS

                  A.       Rent Adjustments

                  Paragraph "4. RENT, (b)" of the Lease is amended and modified
         to provide as follows:

                  "(b) Except as provided in `(f)' below, on or before the first
                  day of each and every month of each thirty six (36) month
                  period (the `Adjustment Period'), the first of which shall
                  commence August 1, 1986 in addition to the Fixed Rent due
                  pursuant to subparagraph (a) above, Tenant shall pay as
                  additional rent an additional amount (the `Adjustment') to be
                  determined in accordance with the with the variations, if any,
                  in the costs of living as shown by the Consumer Price Index
                  for all Urban Consumers, as published by the Bureau of Labor
                  Statistics, United States Department of Labor, or any
                  successor agency (the `CPI'). The Adjustment for each month of
                  each Adjustment Period shall be an amount equal to fifty per
                  cent (50%) of the difference between (i) the product obtained
                  by multiplying the Fixed Rent by a fraction, the numerator of
                  which shall equal the CPI reported for the fourth calendar
                  month immediately prior to the first day of such Adjustment
                  Period and the denominator of which shall equal the CPI
                  reported for the fourth calendar month preceding the
                  Commencement Date, or, if a Market Reappraisal Date has
                  occurred, then the fourth calendar month preceding the most
                  recent Market Reappraisal Date and (ii) the Fixed Rent. The
                  computation of the Adjustment for each month of each
                  Adjustment Period shall be made without regard to whether any

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                  Adjustment was payable with respect to any preceding
                  Adjustment Period. In no event shall the calculation of the
                  amount of the Adjustment operate to reduce the total paragraph
                  3 below the Fixed Rent. In the event, that the necessary CPI
                  figures are not available to compute the Adjustment upon the
                  commencement of any Adjustment Period, Tenant shalt continue
                  to pay the Fixed Rent plus the Adjustment in effect, if any,
                  for the prior Adjustment Period (the `Tentative Adjustment' )
                  until such CPI figures become avail-able, at which time the
                  appropriate Adjustment for each month of such Adjustment
                  Period shall be determined. Immediately following such
                  determination, either Landlord shall refund to Tenant the
                  amount by which the sum of all Tentative Adjustments actually
                  paid during such Adjustment Period exceeds the sum of all
                  Adjustments properly payable during such Adjustment Period, or
                  Tenant shall pay to Landlord the amount by which the sum of
                  all Adjustments properly payable during such Adjustment Period
                  exceeds the sum of all Tentative Adjustments actually paid
                  during such Adjustment Period. In the event the CPI is no
                  longer published, Landlord and Tenant shall determine another
                  index of similar nature showing changes in the cost of living
                  to be used to calculate the Adjustment due Landlord. If
                  Landlord and Tenant cannot agree on the selection of an index
                  or if Landlord and Tenant disagree as to the computations
                  called for in this subparagraph (b), any disagreed matters
                  shall then be resolved by arbitration in the county in which
                  the Premises are located, in accordance with the then rules of
                  the American Arbitration Association. The Fixed Rent and any
                  Adjustments are sometimes collectively referred to as the
                  `Rent'."

                  B.       Periodic Reappraisals

                  The Lease is supplemented by the addition to "4. RENT" of the
         Lease of the following subparagraph "(f)":

                  "(f) For the purpose of this Lease the term `Market
                  Reappraisal Date' shall mean, if Tenant exercises its option
                  to extend the Term of the Lease, the first day of the 120th
                  month of the Term and the first day of the 180th month of the
                  Term. On each Market Reappraisal Date during the Term of this
                  Lease, the Fixed Rent shall be adjusted to the then fair
                  market rental value (hereinafter `Fair Rental Value') of the
                  Premises as determined below; and in no event shall the amount
                  of the Fixed Rent, after such adjustment, be less than the
                  Fixed Rent in effect immediately prior to such adjustment.
                  There shall be no Adjustment (as defined in `(b)' above) paid
                  during the period following the Market Reappraisal Date until
                  the commencement of the next Adjustment Period and thereupon
                  the Fixed Rent, as adjusted pursuant to this paragraph '(f)'
                  shall be the Fixed Rent for purposes of computing adjustments
                  pursuant to paragraph determining the Fair Rental Value of the
                  Premises, leasehold improvements made during the Term of the
                  Lease, at the sole cost and expense of Tenant (exclusive of
                  any allowance or contribution of Landlord) shall not be
                  considered a part of, or included in, the determination of the
                  Fair Rental Value.

                  Landlord shall give the Tenant notice of Landlord's
                  determination of the Fair Rental Value (the `Landlord's
                  Determination') on or before the Market Reappraisal Date in
                  question. Landlord's Determination shall be the Fair Rental
                  Value of the Premises unless Tenant, within ten (10) days
                  after Tenant's receipt of the Landlord's Determination, gives
                  notice in writing to Landlord that Tenant objects to
                  Landlord's determination and sets forth Tenant's determination
                  of Fair Rental Value (the `Tenant's Determination').
                  Thereafter, Landlord and Tenant may negotiate to establish the

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                  Fair Rental Value, or Landlord may employ and pay an MAI real
                  property appraiser to determine the Fair Rental Value and
                  submit to Tenant and Landlord a report of such appraisal (the
                  `Landlord's Appraisal'). If Landlord employs an MAI real
                  property appraiser, Tenant shall also employ an MAI real
                  property appraiser to determine the Fair Rental Value and to
                  submit an appraisal report to Landlord and Tenant (the
                  `Tenant's Appraisal'). If Landlord's and Tenant's Appraisals
                  differ by less than five percent (5%), the greater of the two
                  shall be the Fair Rental Value if Landlord's and Tenant's
                  Appraisals differ by more than five percent (5%), Landlord and
                  Tenant shall each instruct their respective appraisers to
                  jointly appoint a third appraiser to determine the fair market
                  rental value (the `Third Appraisal'), and each shall pay
                  one--half (1/2) the cost of the Third Appraisal. Whichever of
                  the three appraisals is the furthest from the median shall be
                  disregarded, and the average of the remaining two shall be the
                  Fair Rental Value binding upon Tenant and Landlord. If the
                  Fair Rental Value, has not been determined before the Market
                  Reappraisal Date in question, Tenant shall pay to Landlord the
                  amount set forth in Landlord's Determination until the Fair
                  Rental Value has been determined. If the Fair Rental Value
                  finally determined is less than the Landlord's Determination,
                  Landlord agrees to credit any over-payments made by Tenant to
                  the next due installments, of Fixed Rent. Landlord and Tenant
                  shall each bear the fees and expenses of their respective
                  appraisers and, the fees and expenses of the third appraiser,
                  if any, shall be shared equally by Landlord and Tenant."

                  C.       Term

                  The definition of "Term" as set forth on page 1 of the Lease
         is amended and modified to provide as follows:

                  "Term (paragraph 3): 120 Months"

                  D.       Fixed Rent

                  The definition of "Fixed Rent" as set forth on page 1 of the
         Lease is amended and modified to provide as follows:

                  "Fixed Rent (paragraph 4(a)): $87,695.00."

                  E.       Commencement Date

                  The definition of the "Commencement Date" as set forth on page
1 of the Lease is amended and modified to provide as follows:

                  "Commencement Date" (paragraph 3): August 1, 1983."

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                  F.       Right of First Refusal

                  If, at any time during the term of this Lease, Landlord shall
receive a bona fide offer from any third person to purchase the premises or
shall make a bona fide offer to any third person to sell the premises, Landlord
shall in either event, prior to the execution of a contract with said third
person, serve upon the Tenant a notice (herein "Notice of Offer") in writing
describing in detail the terms of such offer and the intention of Landlord to
accept the same. The Tenant shall have the right for 30 days thereafter to
notify Landlord, in writing, of its intent to purchase the premises on the terms
and provisions set forth in the Notice of Offer. Tenant agrees that Tenant
shall, within 14 days from the date Tenant gives Landlord Tenant's notice of
intent to purchase, execute a contract to purchase the premises upon the terms
and conditions set forth in the Notice of Offer. If Tenant shall not within the
30 day period elect to acquire the premises upon the terms and conditions set
forth in the Notice of Offer, the Landlord may then sell the premises to said
third person provided said sale is on the terms and conditions and for the price
set forth in the Notice of Offer. If Tenant fails to execute a contract to
purchase the premises within 14 days following Tenant's giving of its notice of
intent to purchase to Landlord, then Landlord shall have the same rights as if
Tenant shall have not elected to acquire the premises and, in addition, Tenant
shall be deemed to have committed a non-curable material default under the terms
and provisions of the Lease.

                  G.       Extension

                           (1)      Generally

                           The Lease is hereby amended and supplemented so as to
provide the Tenant herein the right to extend the Term of the Lease in
accordance with the terms of this section "G. Extension" for one (1) ten year
extension commencing on the expiration of the original term (e.g., July 31,
1993) and terminating 120 months thereafter (e.g., July 31, 2003).

                           (2)      Exercise of Extension

                           Landlord hereby grants to Tenant the right to extend
the initial Lease Term for the extension described above; provided that, the
exercise of such extension shall be strictly conditioned upon the satisfaction,
or written waiver by Landlord, of the following terms and conditions:

                           (a) Tenant shall give written notice to Landlord of
its election to exercise the extension not later than 90 days prior to the end
of the initial Lease Term; and

                           (b) Upon the commencement of the extension this Lease
shall be in full force and effect and Tenant shall not be in breach of or in
default under any provision of the Lease.

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                  (3)      Effect of Extension

                  The extension shall be deemed to be a continuation of the
initial Term of the Lease and shall not be deemed to be the commencement of a
new term. Adjustments and reappraisals resulting in increases in rent under the
Lease shall continue in the manner provided for in the Lease following the
commencement of the extended Term as if the extended Term had originally been a
portion of the original Term of the Lease.

         III.     EFFECT OF AMENDMENT

                  Except as expressly amended or modified herein the Lease shall
remain in full force and effect.

                                             "Landlord"

                                             SIERRA EQUITIES, INC.,
                                             a corporation

Dated: August 11,1983                        By: /s/ SHIRLEY HOUGH
                                                 ---------------------------
                                             Title: Vice President/Secretary

                                             "Tenant"
                                             MESA GENERAL HOSPITAL, INC.,
                                             an Arizona corporation

Dated: August 11, 1983                       By: /s/
                                                ---------------------------
                                                 Title: President

                                       5<PAGE>   1
                                                                   EXHIBIT 10.22

                          MESA GENERAL HOSPITAL - LEASE
                              CONFORMING AMENDMENT
                                       TO
                                      LEASE

         This Conforming Amendment to Lease (the "Amendment") is made and
entered into as of the 10th day of June, 1991 by and between Sierra Equities,
Inc., a California corporation (the "Lessor") and Mesa General Hospital, Inc.,
an Arizona corporation (the "Lessee") based upon the following facts:

         A. Lessor and Lessee are parties to the following lease documents
(collectively, the "Lease") relating to certain leased premises more
particularly described therein (the "Premises"):

         1. Lease dated July 29, 1977 between Sierra Equities, Inc., a
California corporation, and Mesa General Hospital, Inc., an Arizona corporation;

         2. Amendment to Lease entered into October 20, l978 between Sierra
Equities, Inc., a California corporation, and Mesa General Hospital, Inc., an
Arizona corporation;

         3. Assignment and Lease effective July 1, 1982 from Mesa General
Hospital, Inc., an Arizona corporation to Summit Health Ltd., a California
corporation;

         4. Second Amendment to Lease entered into July, 1982 between Sierra
Equities, Inc., a California corporation, and Summit Health Ltd., a California
corporation; and

         5. Addendum to Lease dated August 11, 1983 between Sierra Equities,
Inc., a California corporation, and Mesa General Hospital, Inc., an Arizona
corporation.

         B. Lessor and Lessee desire to amend the Lease on the terms and
conditions set forth herein.

         Based on the foregoing, and for other good and valuable consideration,
the receipt and adequacy of which are hereby acknowledged, the parties hereto
agree as follows:

         1. TERM. The term of the Lease is extended to July 31, 2003, on the
terms and conditions contained in the Lease as modified hereby.

         2. OPTION TO EXTEND.

            (a) Lessor hereby grants, upon and subject to the terms and
conditions contained in this paragraph, Lessee the options to extend (the
"Options to Extend") the initial term (the "Initial Term") of the Lease (as
extended pursuant to paragraph 1 above) for two additional ten year periods (the
first such ten year period, the "First Option Term," the second such ten year
period, the "Second Option Term," and the First Option Term and the Second
Option Term, collectively, the "Extended Term"), commencing immediately
following the expiration of the Initial Term. Provided that Lessee is not then
in default under the terms of the Lease (and, as respects the second Option to
Extend, provided that Lessee has exercised the first Option to Extend) Lessee
may exercise the applicable Option to Extend at any time during the period
commencing on August 1, 1993, and ending on April 30, 2003 (as respects the
first option to Extend) and April 30, 2013 (as respects the second Option to

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Extend), which exercise shall be by written notice delivered to Lessor in
accordance with the applicable terms of the Lease. The terms and conditions of
the Lease during the Extended Term shall be the same as contained in the Lease
(as amended or otherwise modified), except that the rent shall be adjusted as
provided below. As used in the Lease, the phrase "Lease Term" means, if the
context so requires, the Initial Term and the Extended Term.

            (b) Unless Lessor shall have elected, by written notice to Lessee
given in accordance with the applicable terms of the Lease on or before April
30, 2003 (as respects the first Option to Extend) and April 30, 2013 (as
respects the second Option to Extend), to have subparagraph 2(c) below apply in
lieu of this subparagraph 2(b), the monthly rent payable during each 24 month
period of the First Option Term or the Second Option Term, as the case may be
(each such 24 month period, the "Adjustment Period") shall be increased above
the monthly rent, as theretofore adjusted, for each month of the immediately
preceding 24 month period (each such 24 month period, the "Base Period") by an
amount equal to the product obtained by multiplying the rent payable for the
Base Period (as theretofore adjusted) by a fraction, the numerator of which
shall be the CPI (as defined below) published for the month of June preceding
the Adjustment Period and the denominator of which shall be the CPI published
for the month of June preceding the Base Period; provided, however, that in no
event shall the rent for any Adjustment Period be less than 100% of, or more
than 110% of, the rent for the applicable Base Period. "CPI" means the Consumer
Price Index for All Urban Consumers, All Items, U.S. City Average, utilizing the
latest base year adopted for such Index, as reported by the Bureau of Labor
Statistics of the United States Department of Labor or any successor agency;
provided, however, that notwithstanding anything to the contrary contained in
this paragraph, the two CPIs used in computing the foregoing fraction shall in
all cases utilize the same base year. If the CPI ceases to be published or if
for any reason the foregoing computation cannot be based upon such changes in
the CPI, it shall be based upon changes in another index to be selected by
Lessor that enjoys general recognition and acceptance as an indicator of changes
in consumer prices.

            (c) In the event that Lessor shall timely make the election to cause
the provisions of this subparagraph 2(c) to apply to the First Option Term or
the Second Option Term, as the case may be, instead of those contained in
subparagraph 2(b), then:

                (i) The monthly rent payable during each month of the First
Option Term or the Second Option Term, as the case may be (each such month, the
"Adjustment Month",) shall be increased above the monthly rent, as theretofore
adjusted, for the same month of the immediately preceding calendar year (the
"Base Month") by an amount equal to 1/12 of 5% of the amount (if any) by which
Lessee's Gross Revenues (as defined below) for the calendar year in which the
Adjustment Month occurs exceed Lessee's Gross Revenues for the calendar year in
which the Base Month occurs; provided, however, that in no event shall the rent
for any Adjustment Month be less than the rent for the applicable Base Month.
Any increased rent payable with respect to any Adjustment Month shall be paid
within ten days of the calculation of Gross Revenues relative to the calendar
year in which such Adjustment Month occurs, and regardless of whether the Lease
Term shall have previously expired.

                (ii) The term "Gross Revenues" for purposes of this Lease shall
equal (i) Lessee's total revenues relative to its operations on the Premises
less (ii) provisions for uncompensated care, contractual allowances, discounts,
receivable valuation reserves, and physician professional fees billed by Lessee,
nonoperating revenues such as interest income or income from the sale of assets

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not sold in the ordinary course of business, and revenues for services provided
off the Premises. Gross Revenues for the first adjustment month shall not
include adjustments not in the ordinary course of business for periods prior to
the Lessor's election, such as prior year cost reports settlements.

                (iii) Lessee shall submit to Lessor no later than March 30 of
each year commencing with the calendar year 2003 a written statement signed by
Lessee's certified public accountants, showing in reasonable detail the amount
of Gross Revenues for the preceding calendar year.

                (iv) Lessee agrees to prepare and keep in its possession and
available to Lessor for a period of not less than two years following the end of
each calendar year (i) adequate records which shall show and support the
computation of the Gross Revenues for each of such calendar year and (ii) the
income, sales and occupation tax returns of Lessee for each month of such
calendar year.

                (v) Lessor or its designated agents shall have the right, at any
reasonable time during regular business hours and from time to time after giving
reasonable written notice at least 48 hours in advance, to do any or all of the
following:

(A) audit the records of Lessee with respect to any statement for a particular
year which may be audited in accordance with the provisions of subparagraph (iv)
above; (B) cause an audit of such records to be made; and (C) make abstracts
from such records and to make copies of any or all of such records. Lessee shall
make all such records specified in such written notice available at the time
specified in such notice, if reasonable, and at the place where the records are
kept. If the audit discloses that the Gross Revenues for any year have been
understated resulting in a reduced payment of rent to Lessor, Lessee shall
immediately pay the additional rent to Lessor and, in addition thereto, interest
thereon at the rate of 10% simple interest per annum from the date such sums
would otherwise be payable. It the audit discloses that the Gross Revenues for
any calendar year were understated by more than two percent, Lessee shall also
reimburse Lessor for the cost of the audit. All information obtained by Lessor
in the course of any such audit or otherwise obtained under the provisions of
subparagraph 2(c) this Lease shall be treated as confidential except in any
litigation or arbitration proceedings between Lessor and Lessee.

                (vi) The acceptance by Lessor of payments of rent shall be
without prejudice to Lessor's right to an audit of Lessee's records of its Gross
Revenues in order to verify the amount of Gross Revenues received by Lessee.

         3. RIGHT OF FIRST REFUSAL. Any right of first refusal in favor of
Lessee contained in the Lease is hereby deleted in its entirety. Lessor hereby
grants Lessee a right of first refusal (the "Purchase Right") to acquire the
Premises on the following terms and conditions:

            (a) The Purchase Right shall only be exercisable during the Purchase
Right Period (as defined below) and in the event (1) Lessor receives a third
party offer (the "Third Party Purchase Offer") to sell, transfer or otherwise
convey the Premises which Lessor is prepared to accept or (2) Lessor makes an
offer (the "Lessor Purchase Offer") to a third party to sell, transfer or
otherwise convey the Premises to the third party and the third party is prepared
to accept such offer. "Purchase Right Period" means the period commencing on the
date of this Lease and ending at midnight on the 90th day following the
expiration of the Lease Term, as the same may be amended or modified from time
to time.

            (b) If Lessor receives, during the Purchase Right Period, a Third
Party Purchase Offer which it is prepared to accept or makes a Lessor Purchase
Offer which a third party is prepared to accept, Lessor shall immediately notify
Lessee thereof in the manner provided below, such notice to contain a copy of

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the Third Party Purchase Offer or the Lessor Purchase Offer, as the case may be,
and all of the terms and conditions thereof. Upon Lessee's receipt of such
notice, Lessee shall have ten days to notify Lessor as to whether or not Lessee
elects to exercise the Purchase Right. In the event that Lessee exercises the
Purchase Right as provided above, Lessor and Lessee, within 30 days after such
exercise, shall execute and deliver escrow instructions and other documents and
do such other acts as shall be necessary or desirable in connection with the
conveyance of the Premises to Lessee in accordance with the Third Party Purchase
Offer or the Lessor Purchase Offer, as the case may be. If Lessee fails to
exercise the Purchase Right within the time period provided above, then Lessor
shall have the right to convey the Premises to the purchaser named in the Third
Party Purchase Offer or the Lessor Purchase Offer, provided that such sale is on
substantially the same terms as are contained in the Third Party Purchase Offer
or the Lessor Purchase Offer and is consummated within 180 days of the date of
Lessor's initial notice to Lessee. Upon the completion of such conveyance, the
Purchase Right shall terminate and be of no further force and effect with
respect to subsequent conveyances of the Premises. If such conveyance is not
completed within such period or if the Third Party Purchase Otter or the Lessor
Purchase Offer is materially modified, Lessor shall comply again with the
provisions of this paragraph prior to any sale, transfer or other conveyance of
the Premises.

            (c) The Purchase Right shall not be applicable with respect to any
public offering by Lessor, transfers in bulk by Lessor of its assets, or
transfers by Lessor to any of its affiliates.

         4. Except as provided in this Amendment, all of the terms and
provisions of the Lease remain unmodified and in full force and effect.

         IN WITNESS WHEREOF, Lessor and Lessee have executed this Amendment as
of the date and year first above written.

         LESSOR:                            Sierra Equities, Inc., a
                                            California corporation

                                            By: /s/
                                              --------------------------------
                                              Its:     PRESIDENT
                                              --------------------------------

         LESSEE:                            Mesa General Hospital, Inc.,
                                            an Arizona corporation

                                            By: /s/
                                              --------------------------------
                                              Its:     PRESIDENT
                                              --------------------------------

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