Exhibit 99.1

21ST CENTURY ONCOLOGY HOLDINGS, INC.

21ST CENTURY ONCOLOGY HOLDINGS INC. REPORTS PRELIMINARY THIRD QUARTER 2015 FINANCIAL RESULTS

FORT MYERS, FL, November 16, 2015 — 21st Century Oncology Holdings, Inc. (“21C or the “Company”), the leading global, physician-led provider of integrated cancer care (“ICC”) services, announced today its financial results for the third quarter ended September 30, 2015.

Dr. Daniel Dosoretz, Founder, President and Chief Executive Officer, commented, “Although the financial results for the third quarter were disappointing, we are pleased with our continued organic performance and cash flow generation ability. In June 2015, ASTRO published coding guidance on its website advising providers to discontinue reporting the treatment simulation code when IMRT treatment planning is ordered.  We subsequently amended our coding policy to align with this guidance on July 1, which resulted in a net reimbursement decline. Additionally, during the quarter changes in treatment modality became more prevalent. The change resulted in a fewer number of treatments delivered due to improved technology that has allowed our physicians to treat certain tumors utilizing a more-intensive radiation dose, but with a fewer number of fractions. As the largest global provider of radiation therapy delivery we are at the forefront of implementing the latest advances in clinical radiation practices throughout our network.”

Dr. Dosoretz continued, “Our fourth quarter cases per day, which of course means an increase in new patients, are trending above third quarter levels, causing me to be optimistic in regards to our 4th quarter performance and for 2016. Our integration of SFRO is on schedule, and we expect to realize significant synergies from fully combining this operation with the existing 21C operations in 2016. Our recent acquisitions, joint ventures and international operations continue to perform well and have outstanding long-term prospects. We remain focused on providing the necessary technology, clinical best practices, and high quality operating support to our physician network, so as to provide them with the tools and resources to achieve superior outcomes.”

Third Quarter 2015 Results

Total pro forma revenues for the third quarter of 2015 were $258.2 million, up slightly compared to total pro-forma revenues of $257.6 million in the same quarter of 2014. Revenue growth from acquired and new operations as well as our international business was offset by approximately $2.3 million from simulation code bundling, approximately $3.3 million from a change in treatment modality, which resulted in fewer treatments per radiation oncology case, and $5.4 million of revenue adjustments at Medical Developers resulting from a correction in our revenue recognition process.

While total radiation oncology cases completed during the quarter increased 1.6%, revenue per radiation oncology case declined 3.8% due to modality shifts, particularly in breast and lung cases, along with the simulation code for IMRT cases now being combined with the planning code.

Pro Forma Adjusted EBITDA in the third quarter of 2015 was $27.2 million, or 10.5% of total pro forma revenues, as compared to $39.7 million, or 15.4% of total pro forma revenues, in the third quarter of 2014. The primary contributors to the EBITDA decline were the aforementioned $11.0 million of items affecting revenue combined with $4.2 million of additional compensation and benefits expenses and $1.1 million of minority interest distributions, partially offset by $2.5 million from acquisitions and $2.7 million resulting primarily from the ongoing implementation of our savings and synergies initiatives.

Total pro forma revenues for the nine months ended September 30, 2015 were $822.9 million, up 7.5% compared to total pro forma revenues of $765.7 million for the first nine months of 2014. Same store total radiation cases completed during the first nine months increased 6.6%, but same store revenues per completed radiation case declined 6.0% due to the impact of modality and the simulation code change. Pro Forma Adjusted EBITDA was $124.3 million for the nine months ended September 30, 2015, up 6.9% compared to $116.3 million for the first nine months ended September 30, 2014.  Pro-forma EBITDA margin was essentially flat for the two nine month periods.

Recent Developments

As previously announced, on July 2, 2015 we purchased the remaining 35% of SFRO for $44.1 million. Consideration for the purchase was comprised of $15.0 million in cash, $14.6 million in a seller financing note, and $14.5 million in 21st Century Oncology Investments LLC preferred stock.  The integration of SFRO continued during the quarter and is expected to be completed by March 31, 2016.

On August 1, 2015, 21C purchased a controlling stake in a joint venture with a leading oncology group.  This purchase resulted in the two entities having a controlling interest in the hospital based radiation center located at the Hospital Manuel Uribe Angel de Envigado in Medellin, Colombia.

On Friday October 30, 2015, CMS released the 2016 Physician Fee Schedule Final Rule, which includes an approximate 2% reduction to overall radiation oncology and an approximate 2.7% reduction to overall freestanding center reimbursement. Based on the Company’s preliminary

review of the Final Rule and its impact on its treatment and reimbursement code mix, the Company estimates the final rule will negatively impact its full year 2016 EBITDA by approximately $7-$9 million, down from an estimated $17-$20 million after the release of the 2016 Physician Fee Schedule Preliminary Rule. We have a dynamic and flexible infrastructure and remain the global leader in clinical quality and cost effectiveness, with an ICC model that has proven its ability to deliver same store volumes and incremental market share gains. Given these unique attributes, we remain the best-positioned provider to thrive in a wide range of different reimbursement scenarios.

Earnings Release Special Note:

During the quarter the Company changed its independent registered public accounting firm.  The Company continues to work with its independent accountants in finalizing their review of the Company’s financial statements for filing with the SEC on Form 10-Q for the quarter ended September 30, 2015. While adjustments may be made to these preliminary financial statements, the Company does not believe that the completion of this process will result in a material change to the preliminary Pro-Forma Adjusted EBITDA calculation nor the preliminary condensed consolidated statements of operations, comprehensive loss and cash flows results presented herein.

Conference Call

The Company will host a conference call on Monday, November 16, 2015 at 2:00 p.m. Eastern Time, during which management will discuss its financial results in further detail. The dial-in numbers are (877) 407-9039 for domestic callers and (201) 689-8470 for international callers.  In addition, a telephonic replay of the call will be available until November 30, 2015.  The replay dial-in numbers are (877) 870-5176 for domestic callers and (858) 384-5517 for international callers.  Please use the conference ID number 13622067 to access the replay.

A live webcast and webcast replay of the call will also be available from the Events section on the corporate web site at www.21co.com.

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 September 30, 2015, the Company operated 182 treatment centers, including 146 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, including, but not limited to, the Company’s expected financial results and estimates for 2015 and the effects of the CMS’s Final Rule for the 2016 Physician Fee Schedule on its results.  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)

(unaudited)

21ST CENTURY ONCOLOGY HOLDINGS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS

(in thousands)

(unaudited)

21ST CENTURY ONCOLOGY HOLDINGS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(in thousands)

(unaudited)

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.

(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) Other non-cash income / expense items include: gain on BP settlement, equity initial public offering expenses, loss on sale lease back transaction, fair value adjustment of noncontrolling interest and earn-out liabilities, fair value adjustment of embedded derivative, gain on foreign currency derivative contracts, sale-lease back adjustments.

(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) PRELIMINARY

* Total cases completed represents a count of patients that have completed their course of treatment. Total case counts are based on legacy and acquired clinical systems.