Exhibit 99.1

21ST CENTURY ONCOLOGY HOLDINGS, INC.

21ST CENTURY ONCOLOGY HOLDINGS INC. REPORTS FOURTH QUARTER AND FULL YEAR 2015 FINANCIAL RESULTS

COMPLETES FINANCIAL RESTATEMENT

FORT MYERS, FL, August XX, 2016 — 21st Century Oncology Holdings, Inc. (“21C” or the “Company”), the leading global, physician-led provider of integrated cancer care services, announced today its financial results for the fourth quarter and full year ended December 31, 2015 and announced the completion of the restatement of financial results for the years ended December 31, 2012, 2013 and 2014, the unaudited condensed consolidated financial statements as of and for each of the interim periods within the years ended December 31, 2012, 2013 and 2014 and for the interim periods ended March 31, June 30, and September 30, 2015.

Fourth Quarter 2015 and Full Year 2015 Results

Total revenues for the fourth quarter of 2015 were $263.1 million, down 1.3% as compared to total revenues of $266.6 million in the same quarter of 2014. Revenue growth from acquired and new operations was offset by approximately $3.3 million relative to the effect of simulation code bundling. Net income for the fourth quarter was $7.0 million versus a net loss of $28.3 million for the same period in the prior year. The improvement in net income resulted from a fair market value adjustment for embedded derivatives.

Pro-forma adjusted EBITDA in the fourth quarter of 2015 was $38.8 million, or 14.7% of total pro-forma revenues, as compared to $30.7 million, or 11.5% of total pro-forma revenues, in the fourth quarter of 2014. The primary contributor to the pro-forma adjusted EBITDA improvement was a $6.2 million reduction in compensation expense and $5.1 million improvement in bad debt offset by the $3.5 million decrease in total revenues.

Total radiation oncology treatments per day during the fourth quarter increased 1.8% over the same period in the prior year and same market radiation oncology treatments per day for the quarter declined 2.0% compared to the same period in the prior year. As previously disclosed,

the Company has experienced a decrease in treatments per case for breast and lung diagnoses, as a result of technological innovations.

Net patient service revenue per radiation oncology treatment declined 1.1% in the fourth quarter of 2015 relative to the same period last year. This was largely driven by the simulation code for IMRT cases being bundled with the planning code. The impact of the bundling code change in the fourth quarter of 2015 was $3.3 million.

Total revenues for full year 2015 were $1,079.2 million as compared to $1,018.2 million in 2014. The net loss for 2015 was $126.8 million as compared to a net loss of $352.7 million in 2014. The improvement in the net loss was due to recording a $229.5 million impairment loss in 2014.

Total pro-forma revenues for full year 2015 were $1,080.3 million, an increase of 5.2% year over year. Pro-forma adjusted EBITDA was $159.1 million for 2015, an increase of 12.9% as compared to $141.0 million in 2014. The increase in pro-forma adjusted EBITDA was primarily driven by a $53.3 million increase in total pro-forma revenues offset by a $34.5 million increase in salaries and benefits. Pro-forma adjusted EBITDA margin for 2015 increased 1.0% as compared to 2014.

Total radiation oncology treatments per day for 2015 increased 4.2% year over year, reflecting the impact of strategic acquisitions made earlier in 2015. Same market radiation oncology treatments per day decreased 1.6% year over year due to the reduction in treatments per case, particularly breast and lung diagnoses. For 2015, net patient service revenue per radiation oncology treatment declined 1.9% and same market net patient service revenue per radiation oncology treatment declined 0.6%, each as compared to 2014, due to the impact of the simulation code change.

Dr. Daniel Dosoretz, Founder, President and Chief Executive Officer, commented, “We finished the fourth quarter and full year 2015 with positive momentum in our business. We are pleased with our performance against the backdrop of headwinds from simulation code bundling and a reduction in treatments per day due to advances in hypo-fractionated external beam radiotherapy and stereotactic radiosurgery.”

Restatement of Financial Results

On March 24, 2016, the Board of Directors of 21C (the “Board”) determined that the financial statements for all interim periods and years ended December 31, 2012, 2013 and 2014 as well as the first three periods of 2015, should be restated. The restatement was primarily related to revenue recognition matters, accounts receivable reconciliation issues and income and non-income tax matters with respect to operations in Latin America as well as to give effect to refunds and payment adjustments that the Company recorded in connection with electronic health records incentive payments received under the Health Information Technology for Economic and Clinical Health Act (HITECH).

Management remains committed to remediating the material weaknesses identified in its internal controls over financial reporting as well as other areas of risk that led to the restatement of financial results. Several specific remediation initiatives have already been implemented and we believe on-going efforts will continue to improve the effectiveness of our internal control environment.

Robert L. Rosner, Chairman of the Board of Directors and Chair of The Executive Committee, said, “While the last nine months have included some unique challenges for 21C, the Board and management believe we will emerge from this process a stronger and more focused organization. After a diligent and comprehensive review, we have identified areas in our financial and compliance procedures in need of remediation and have constructed a robust plan to address those issues. The Company is thoroughly committed to executing that plan and maintaining the highest levels of compliance going forward. The importance of these initiatives has been and will continue to be communicated to every 21C employee.”

Debt Agreements

On August 15, 2016, 21C entered into amendment and waiver agreements with certain creditors. The agreements, among other things, waive the event of default for failure to file financial statements for the year ended December 31, 2015 until September 10, 2016, and waive the event of default for failure to file financial statements for the quarters ended March 31, and June 30, 2016 until September 30, 2016. The amendment agreements require 21C to complete three separate capital events to receive the lessor of, 1) net cash proceeds from the issuance or sale of 21C’s capital stock or from other equity investments and/or sales of assets for a total aggregate amount of $125.0 million, or 2) an amount such that following the third capital event 21C’s cash and cash equivalents plus unused revolving loan commitments equals at least $120.0 million and 21C’s consolidated leverage ratio is not greater than 6.4 to 1.0. The amendment agreements also require the Company to maintain minimum liquidity of $40.0 million.

Reimbursement

The United States Congress unanimously passed the Patient Access and Medicare Protection Act (S. 2425) which freezes radiation oncology freestanding payment rates for treatment delivery and image guidance codes in 2017 and 2018 at levels set for 2016. The bill was signed into law by President Obama on December 28, 2015. In 2019, CMS will transition to a new episodic alternative payment model. The legislation requires the Secretary of Health and Human Services to submit to Congress a report on the development of an episodic alternative payment model for reimbursement under the Medicare program within 18 months.

Dr. Dosoretz, concluded, “We applaud Congress and President Obama for their dedication to working together with the industry to advance payment reform and achieve payment predictability while ensuring patient access to quality cancer care. This is an exceptional example of how bipartisan collaboration can deliver a meaningful benefit to patients in need of the most advanced technologies available in radiation therapy. We look forward to working with policymakers over the next few years on developing an alternative payment model which will provide continued access to sophisticated radiation therapy treatment for patients for years to come.”

About 21st Century Oncology Holdings, Inc.

21st Century Oncology Holdings, Inc. is the largest global, physician led provider of integrated cancer care services. The Company offers a comprehensive range of cancer treatment services, focused on delivering academic quality, cost-effective patient care in personal and convenient

settings. As of December 31, 2015, the Company operated 181 treatment centers, including 145 centers located in 17 U.S. states and 36 centers located in seven countries in Latin America.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Act of 1934, as amended. Statements preceded by, followed by or that otherwise include the words “believes”, “expects”, “anticipates”, “intends”, “projects”, “estimates”, “plans”, “may increase”, “forecast” and similar expressions or future or conditional verbs such as “will”, “should”, “would”, “may” and “could” are generally forward-looking in nature and not historical facts. Forward-looking statements are based on management’s current expectations or beliefs about the Company’s future plans, expectations and objectives. These forward-looking statements are not historical facts and are subject to risks and uncertainties that could cause the actual results to differ materially from those projected in these forward-looking statements including, but not limited to reductions in Medicare reimbursement, healthcare reform, state and federal investigations, claims and litigation matters, decreases in payments by managed care organizations and other commercial payers  and other risk factors that may be described from time to time in the Company’s filings with the Securities and Exchange Commission. Readers of this release are cautioned not to place undue reliance on forward-looking statements contained herein, which speak only as of the date stated, or if no date is stated, as of the date of this press release. The Company undertakes no obligation to publicly update or revise the forward-looking statements contained herein to reflect changed events or circumstances after the date of this release, unless required by law.

21ST CENTURY ONCOLOGY HOLDINGS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(in thousands, except share amounts)

21ST CENTURY ONCOLOGY HOLDINGS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS

(in thousands)

21ST CENTURY ONCOLOGY HOLDINGS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(in thousands)

21ST CENTURY ONCOLOGY HOLDINGS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(in thousands)

21ST CENTURY ONCOLOGY HOLDINGS, INC.

Supplemental Financial Information (Unaudited)

Reconciliation of Total Pro-forma Revenue and Pro-forma Adjusted EBITDA to Net Loss Attributable

to 21st Century Oncology Holdings, Inc. Shareholder

(1) Pro-Forma Adjusted EBITDA, as defined per the Credit Agreement dated as of April 30, 2015, calculated as income (loss) before interest expense (net of interest income), income taxes, depreciation and amortization, net income attributable to noncontrolling interests, net of cash distributions, gain on the sale of an interest in a joint venture, loss on sale leaseback transaction, early extinguishment of debt, fair value adjustment of earn-out liability, fair value adjustment of embedded derivative, impairment loss, foreign currency derivative contract loss (gain), management fees accrued to our sponsor, non-cash expenses including costs relating to stock compensation, amortization of straight-line rent and amortization of capital expenditures relating to repairs and maintenance, non-cash equipment rent, sale-lease back adjustments, acquisition-related costs, other expenses including loss on sale of assets, severance payments related to termination of employee staff reductions, tail premiums on termed physicians, franchise taxes, costs relating to consulting services on Medicare reimbursement, litigation settlements with physicians, costs associated with tradename and rebranding initiatives, expenses associated with idle / closed radiation therapy treatment facilities and pro-forma full period effect of acquisition EBITDA.

(a) Pro-forma amounts related to adjustments to total revenues and Pro-forma Adjusted EBITDA to reflect the full period effect of our acquisitions and Value Added Services contracts completed during 2015 and 2014.  The adjustments reflect the impact to our total revenues and Pro-forma Adjusted EBITDA as if the acquisitions and Value Added Services contracts had occurred at the beginning of the year.

(b) Other expenses include management fees accrued to our sponsor, Vestar Capital Partners, loss on sale of assets, severance payments related to termination of employee staff reductions, tail premiums paid on terminated physicians, franchise taxes and costs relating to consulting services on Medicare reimbursement. Expenses related to the costs associated with the Company’s tradename and rebranding initiatives and expenses associated with idle / closed radiation therapy facilities, costs associated with the CMS Medicare freeze.

(c) Non-cash expenses including costs relating to stock compensation, amortization of straight-line rent, amortization of capital expenditures relating to warranty arrangements amortized to repairs and maintenance and non-cash equipment rent.

(d) Sale-lease back adjustments relates to the adjustment of benefit derived from the classification of operating leases as finance obligations reflecting a reclassification of interest expense and depreciation and amortization expense as rent expense.

(e) Acquisition related costs associated with ASC 805, “Business Combinations,” including professional fees, corporate development, integration and due diligence costs relating to the acquisition of medical practices.

(f) Litigation matters relate to loss contingency reserves related to the Medicare investigative matters and costs associated with the termination of physicians.

(g) Expenses associated with negotiating with note-holders, recapitalization support agreement and legal and consulting fees associated with management of liquidity.

We believe the Pro-Forma Adjusted EBITDA provides useful information about our financial performance to investors, lenders, financial analysts and rating agencies since these groups have historically used EBITDA-related measures in the healthcare industry, along with other measures, to estimate the value of a company, to make informed investment decisions, to evaluate a company’s leverage capacity and its ability to meet its debt service requirements.  Pro-forma Adjusted EBITDA eliminates the uneven effect of non-cash depreciation of tangibles assets and amortization of intangible assets, much of which results from acquisitions accounted for under the purchase method of accounting.  Pro-forma Adjusted EBITDA is also used by us to measure individual performance for incentive compensation purposes and as an analytical indicator for purposes of allocating resources to our operating business and assessing their performance, both internally and relative to our peers, as well as to evaluate the performance of our operating management teams, and for purposes in the calculation of debt covenants and related disclosures.

Pro-Forma Adjusted EBITDA is not intended as a substitute for net income (loss) attributable to 21st Century Oncology Holdings, Inc. shareholder, operating cash flows or other cash flow data determined in accordance with accounting principles generally accepted in the United States. Due to varying methods of calculation, Pro-forma Adjusted EBITDA as presented may not be comparable to similarly titled measures of other companies.

21ST CENTURY ONCOLOGY HOLDINGS, INC.

KEY OPERATING STATISTICS

(unaudited)