9.125% Senior Secured Note due 2017

Exhibit 4.1

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO., OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

TRANSFERS OF THIS GLOBAL SECURITY SHALL BE LIMITED TO TRANSFERS IN WHOLE, BUT NOT IN PART, TO NOMINEES OF DTC OR TO A SUCCESSOR THEREOF OR SUCH SUCCESSOR’S NOMINEE AND TRANSFERS OF PORTIONS OF THIS GLOBAL SECURITY SHALL BE LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH THE RESTRICTIONS SET FORTH IN THE INDENTURE REFERRED TO ON THE REVERSE HEREOF.

THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”). THE HOLDER HEREOF, BY PURCHASING THIS SECURITY, AGREES FOR THE BENEFIT OF THE COMPANY THAT THIS SECURITY MAY NOT BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED (X) PRIOR TO THE FIRST ANNIVERSARY OF THE ISSUANCE HEREOF (OR ANY PREDECESSOR SECURITY HERETO) OR (Y) BY ANY HOLDER THAT WAS AN AFFILIATE OF THE COMPANY AT ANY TIME DURING THE THREE MONTHS PRECEDING THE DATE OF SUCH TRANSFER, IN EITHER CASE, OTHER THAN (1) TO THE COMPANY, (2) SO LONG AS THIS SECURITY IS ELIGIBLE FOR RESALE PURSUANT TO RULE 144A UNDER THE SECURITIES ACT (“RULE 144A”) TO A PERSON WHOM THE SELLER REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER WITHIN THE MEANING OF RULE 144A, PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER TO WHOM NOTICE IS GIVEN THAT THE RESALE, PLEDGE OR OTHER TRANSFER IS BEING MADE IN RELIANCE ON RULE 144A (AS INDICATED BY THE BOX CHECKED BY THE TRANSFEROR ON THE CERTIFICATE OF TRANSFER ON THE REVERSE OF THIS SECURITY), (3) IN AN OFFSHORE TRANSACTION IN ACCORDANCE WITH REGULATION S UNDER THE SECURITIES ACT (AS INDICATED BY THE BOX CHECKED BY THE TRANSFEROR ON THE CERTIFICATE OF TRANSFER ON THE REVERSE OF THIS SECURITY), (4) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT PROVIDED BY RULE 144 (IF APPLICABLE) UNDER THE SECURITIES ACT, OR (5) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN

EACH CASE IN ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED STATES. THE HOLDER HEREOF, BY PURCHASING THIS SECURITY, REPRESENTS AND AGREES FOR THE BENEFIT OF THE COMPANY THAT IT IS (1) A QUALIFIED INSTITUTIONAL BUYER WITHIN THE MEANING OF RULE 144A OR (2) A NON-U.S. PERSON OUTSIDE THE UNITED STATES WITHIN THE MEANING OF (OR AN ACCOUNT SATISFYING THE REQUIREMENTS OF PARAGRAPH (k)(2)(i) OF RULE 902 UNDER) REGULATION S UNDER THE SECURITIES ACT.

BENEFICIAL OWNERSHIP INTERESTS IN THIS TEMPORARY REGULATION S GLOBAL NOTE WILL NOT BE EXCHANGEABLE FOR INTERESTS IN THE RULE 144A GLOBAL NOTE OR THE PERMANENT REGULATION S GLOBAL NOTE OR ANY OTHER NOTE REPRESENTING AN INTEREST IN THE NOTES REPRESENTED HEREBY WHICH DO NOT CONTAIN A LEGEND CONTAINING RESTRICTIONS ON TRANSFER, UNTIL THE EXPIRATION OF THE “40-DAY DISTRIBUTED COMPLIANCE PERIOD” (WITHIN THE MEANING OF RULE 903(b)(3) OF REGULATION S UNDER THE SECURITIES ACT) AND THEN ONLY UPON CERTIFICATION IN FORM REASONABLY SATISFACTORY TO THE TRUSTEE THAT SUCH BENEFICIAL INTERESTS ARE OWNED EITHER BY NON-U.S. PERSONS OR U.S. PERSONS WHO PURCHASED SUCH INTERESTS IN A TRANSACTION THAT DID NOT REQUIRE REGISTRATION UNDER THE SECURITIES ACT. DURING SUCH 40-DAY DISTRIBUTION COMPLIANCE PERIOD, BENEFICIAL OWNERSHIP INTERESTS IN THIS TEMPORARY REGULATION S GLOBAL NOTE MAY ONLY BE SOLD, PLEDGED OR TRANSFERRED THROUGH THE EUROCLEAR SYSTEM OR CLEARSTREAM BANKING S.A. AND ONLY (A) TO THE COMPANY OR ANY SUBSIDIARY THEREOF, (B) TO A QUALIFIED INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE 144A UNDER THE SECURITIES ACT, (C) OUTSIDE THE UNITED STATES IN AN OFFSHORE TRANSACTION IN COMPLIANCE WITH RULE 904 UNDER THE SECURITIES ACT, (D) PURSUANT TO THE EXEMPTION FROM REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES ACT (IF AVAILABLE), OR (E) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN EACH OF CASES (A) THROUGH (E) IN ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED STATES AND OTHER JURISDICTIONS. HOLDERS OF INTERESTS IN THIS TEMPORARY REGULATION S GLOBAL NOTE WILL NOTIFY ANY PURCHASER OF SUCH RESALE RESTRICTIONS, IF THEN APPLICABLE.

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9.125% Senior Secured Note due 2017

CUSIP No. [          ]

ISIN No. [          ]

US Oncology, Inc., a Delaware corporation, promises to pay to Cede & Co., or registered assigns, the principal sum as set forth on the Schedule of Increases or Decreases annexed hereto on August 15, 2017.

Interest Payment Dates: February 15 and August 15.

Record Dates: February 1 and August 1.

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Additional provisions of this Security are set forth on the other side of this Security.

IN WITNESS WHEREOF, the parties have caused this instrument to be duly executed.

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9.125% Senior Secured Note due 2017

(a) US Oncology, Inc., a Delaware corporation (such corporation, and its successors and assigns under the Indenture hereinafter referred to, being herein called the “Company”), promises to pay interest on the principal amount of this Security at the rate per annum shown above. The Company will pay interest semiannually on February 15 and August 15 of each year, commencing August 15, 2009. Interest on the Securities will accrue from the most recent date to which interest has been paid or, if no interest has been paid, from June 18, 2009. Interest shall be computed on the basis of a 360-day year of twelve 30-day months. The Company shall pay interest on overdue principal at the rate borne by the Securities plus 1% per annum, and it shall pay interest on overdue installments of interest at the rate borne by the Securities to the extent lawful.

(b) Special Interest. The holder of this Security is entitled to the benefits of a Registration Rights Agreement, dated as of June 18, 2009, among the Company, the Subsidiary Guarantors and the Purchasers named therein (the “Registration Agreement”). Capitalized terms used in this paragraph (b) but not defined herein have the meanings assigned to them in the Registration Agreement. In the event that (i) neither the Exchange Offer Registration Statement nor the Shelf Registration Statement has been filed with the Commission on or prior to the 120th day following the date of the original issuance of the Securities, (ii) neither the Exchange Offer Registration Statement nor the Shelf Registration Statement has been declared effective on or prior to the 210th day following the date of the original issuance of the Securities, (iii) neither the Registered Exchange Offer has been consummated nor the Shelf Registration Statement has been declared effective on or prior to the 240th day following the date of the original issuance of the Securities, or (iv) after the Exchange Offer Registration Statement or the Shelf Registration Statement has been declared effective, such Registration Statement thereafter ceases to be effective or usable in connection with resales of the Securities at any time that the Company is obligated to maintain the effectiveness thereof pursuant to the Registration Agreement (each such event referred to in clauses (i) through (iv) above being referred to herein as a “Registration Default”), interest (the “Special Interest”) shall accrue (in addition to stated interest on the Securities) from and including the date on which the first such Registration Default shall occur to but excluding the date on which all Registration Defaults have been cured, at a rate per annum equal to 0.25% of the principal amount of the Securities; provided , however , that such rate per annum shall increase by 0.25% per annum from and including the 91st day after the first such Registration Default (and each successive 91st day thereafter) unless and until all Registration Defaults have been cured; provided further , however , that in no event shall the Special Interest accrue at a rate in excess of 1.00% per annum. The Special Interest will be payable in cash semiannually in arrears each February 15 and August 15.

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The Company will pay interest on the Securities (except defaulted interest) to the Persons who are registered holders of Securities at the close of business on the February 1 or August 1 next preceding the interest payment date even if Securities are canceled after the record date and on or before the interest payment date. Holders must surrender Securities to a Paying Agent to collect principal payments. The Company will pay principal and interest in money of the United States of America that at the time of payment is legal tender for payment of public and private debts. Payments in respect of the Securities represented by a Global Security (including principal, premium and interest) will be made by wire transfer of immediately available funds to the accounts specified by The Depository Trust Company. The Company will make all payments in respect of a Definitive Security (including principal, premium and interest), by mailing a check to the registered address of each Holder thereof; provided , however , that payments on the Securities will be made by wire transfer to a U.S. dollar account maintained by the payee with a bank in the United States if such Holder elects payment by wire transfer by giving written notice to the Trustee or the Paying Agent to such effect designating such account no later than 30 days immediately preceding the relevant due date for payment (or such other date as the Trustee may accept in its discretion).

Initially, Wilmington Trust FSB, a federal savings bank (the “Trustee”), will act as Paying Agent and Registrar. The Company may appoint and change any Paying Agent or Registrar without notice. The Company or any of its domestically incorporated Wholly Owned Restricted Subsidiaries may act as Paying Agent or Registrar.

The Company issued the Securities under an Indenture dated as of June 18, 2009 (the “Indenture”), among the Company, the Subsidiary Guarantors and the Trustee. The terms of the Securities include those stated in the Indenture and those made part of the Indenture by reference to the Trust Indenture Act of 1939 (15 U.S.C. §§ 77aaa-77bbbb) as in effect on the date of the Indenture (the “TIA”). Terms defined in the Indenture and not defined herein have the meanings ascribed thereto in the Indenture. The Securities are subject to all such terms, and Securityholders are referred to the Indenture and the TIA for a statement of those terms.

The Securities are senior secured obligations of the Company. This Security is one of the Offered Securities referred to in the Indenture issued in an aggregate principal amount of $775,000,000. The Securities include the Offered Securities, an unlimited amount of additional Initial Securities that may be issued under the Indenture, and any Exchange Securities issued in exchange for Initial Securities. The Offered Securities, such additional Initial Securities and the Exchange Securities are treated as a single class of securities under the Indenture. The Indenture imposes certain limitations on the ability of the Company and its Restricted Subsidiaries to, among other

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things, make certain Investments and other Restricted Payments, pay dividends and other distributions, incur Debt, enter into consensual restrictions upon the payment of certain dividends and distributions by such Restricted Subsidiaries, issue or sell shares of capital stock of such Restricted Subsidiaries, enter into or permit certain transactions with Affiliates, create or incur Liens, enter into or permit certain Sale and Leaseback Transactions and make Asset Sales. The Indenture also imposes limitations on the ability of the Company to consolidate or merge with or into any other Person or sell, transfer, assign, lease, convey or otherwise dispose of all or substantially all of the Property of the Company.

Except as set forth below, the Securities may not be redeemed at the option of the Company prior to August 15, 2013. On and after that date, the Company may redeem all or any portion of the Securities at once or over time, after giving the required notice under the Indenture. The Securities may be redeemed at the redemption prices set forth below, plus accrued and unpaid interest, if any, to the redemption date (subject to the right of Holders of record on the relevant record date to receive interest due on the relevant interest payment date). The following prices are for Securities redeemed during the 12-month period commencing on August 15 of the years set forth below, and are expressed as percentages of principal amount:

Notwithstanding the foregoing, at any time and from time to time, prior to August 15, 2012, the Company may redeem up to a maximum of 35% of the original aggregate principal amount of the Securities (which includes any additional Securities) with the proceeds from one or more Qualified Equity Offerings (provided that, if the Qualified Equity Offering is an offering by Parent, a portion of the net cash proceeds thereof equal to the amount required to redeem any such Securities is contributed to the equity capital of the Company or used to acquire Capital Stock of the Company (other than Disqualified Stock) from the Company), at a redemption price equal to 109.125% of the principal amount thereof, plus accrued and unpaid interest thereon, if any, to the redemption date (subject to the right of Holders of record on the relevant record date to receive interest due on the relevant interest payment date); provided , however , that after giving effect to any such redemption, at least 65% of the original aggregate principal amount of the Securities remains outstanding. Any such redemption shall be made within 90 days of such Qualified Equity Offering.

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The Company may choose to redeem all or any portion of the Securities, at once or over time, prior to August 15, 2013. If it does so, it may redeem the Securities, after giving the required notice under the Indenture. To redeem the Securities, the Company must pay a redemption price equal to the sum of:

(a) 100% of the principal amount of the Securities to be redeemed, plus

(b) the Applicable Premium,

plus accrued and unpaid interest, if any, to the redemption date (subject to the right of Holders of record on the relevant record date to receive interest due on the relevant interest payment date).

“ Applicable Premium ” means, with respect to any Security at any time, the greater of (1) 1.0% of the principal amount of such Security at such time and (2) the excess of (A) the present value at such time of (i) the redemption price of such Security at August 15, 2013 (such redemption price being described in the table appearing in the first paragraph of this Paragraph (5) exclusive of any accrued interest) plus (ii) any required interest payments due on such Security through August 15, 2013 (including any accrued