Item 1.05 section not located in normalized markdown

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

**Form 8-K**

**CURRENT REPORT**

**Pursuant to Section 13 or 15(d)**

**of the Securities Exchange Act of 1934**

**Date of Report (Date of earliest event
reported) May
20, 2026**

**THE ONCOLOGY INSTITUTE, INC. **

(Exact name of registrant as specified in its charter)

Delaware |
001-39248 |
84-3562323 | ||
| (State or other jurisdiction of incorporation) |
(Commission File Number) | (I.R.S. Employer Identification No.) |

18000 Studebaker Road, Suite 800, Cerritos, CA |
90703 | |
| (Address of principal executive offices) | (Zip Code) |

Registrant’s telephone number, including area
code: **(562) 735-3226**

(Former name or former address, if changed since last report)

**Check the appropriate box below if the Form 8-K
filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:**

☐ Written communication pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communication pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communication pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

**Securities registered pursuant to Section 12(b)
of the Act:**

Title of each class |
Trading Symbol(s) |
Name of each exchange on which registered | ||
| Common stock, par value $0.0001 | TOI | The Nasdaq Stock Market LLC | ||

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐.

**Item 1.05 Material Cybersecurity Incidents.**

The Oncology Institute, Inc. (the “Company”) is providing this disclosure, as a follow-up to its voluntary disclosure in Item 7.01 of a Current Report on Form 8-K filed on November 6, 2025, regarding a cybersecurity incident affecting a software service provider (“Vendor”) utilized by the Company. At the time of the prior voluntary disclosure, the Vendor had indicated that investigation was still ongoing and it could not yet confirm any evidence that any patient personal information was compromised as a result of this incident. However, on May 20, 2026, Kroll, who is the third-party administrator for the Vendor, notified the Company that the Vendor had detected unauthorized access by a third party to certain information systems of the Company, including systems affecting data of patients. The Company believes that the cybersecurity incident has affected various other healthcare service providers, and the Vendor has set up a patient portal through which it intends to provide information and responses to inquiries.

Because of the Company’s technology security and continuity plan, the Company worked swiftly in response, and its operations have continued in all material respects since the detection of the incident. The Company remains committed to protecting the healthcare and other personal information of its patients and will work with the Vendor to offer credit monitoring and protection to all impacted patients.

The Company is reserving all rights with respect to potential claims against relevant third parties or service providers. Although the Company’s investigation and assessment remain ongoing, as of the date of this filing, the Company believes that the incident has not had a material impact on the Company’s operations, financial systems, or its quality of care to its patients, and the Company is currently evaluating any other material impact,