Exhibit 3.31(a)

State of Delaware

Secretary of State

Division of Corporations

Delivered 03:55 PM 09/09/2008

FILED 03:53 PM 09/09/2008

SRV 080938460 – 4597596 FILE

STATE OF DELAWARE

CERTIFICATION OF FORMATION

OF

UNITY ONCOLOGY, LLC

This Certificate of Formation of UNITY ONCOLOGY, LLC is being duly executed and filed by Melisa Jacobs, as an authorized person, to form a limited liability company under the Delaware Limited Liability Company Act (6 Del.C. 18-101, et seq.), as amended.

FIRST. The name of the limited liability company is “UNITY ONCOLOGY, LLC”.

SECOND. The address of its registered office in the State of Delaware is: Corporation Trust Center, 1209 Orange Street, in the City of Wilmington, Delaware 19801. The name of its registered agent as such address is The Corporation Trust Company.

THIRD. This Certificate of Formation shall be effective on September 9, 2008.

IN WITNESS WHEREOF, the undersigned have executed this Certificate of Formation of UNITY ONCOLOGY, LLC this 9th day of September, 2008.

Melisa Jacobs

Authorized Person