The purpose of this study is to find out if radiation therapy (RT) guided by the new reflectance confocal microscopy (RCM)/optical coherence tomography (OCT) device is an effective treatment for basal cell carcinoma (BCC). The researchers will also look at the side effects from RT guided by the RCM/OCT device. In addition, will determine the quality of life before and after treatment by having the participant fill out questionnaires.

Inclusion Criteria:

• Biopsy proven basal cell carcinoma

  °Up to 3 tumors per patient can be treated per protocol synchronously or metachronously

• Clinical stage T1 or T2 by Union International to Control Cancer 8th edition system

  • ≤40 mm in maximum dimension
  • no deep invasion (beyond subcutaneous fat or >6 mm from granular later of dermis to deepest point of carcinoma)
  • no perineural invasion of nerves ≥0.1 mm diameter or deeper than dermis
  • no intraneural invasion
  • no bone erosion, invasion or foraminal transgression NOTE: For the purposes of protocol inclusion, if any of the features mentioned above is not included in the pathology report they will considered absent.

• ≥18 years old

• Amenable to RCM/OCT and radiation therapy in opinion of investigator

  • Some anatomic locations may preclude imaging by RCM/OCT may not be amenable to RCM/OCT imaging
  • Some medical comorbidities may preclude the delivery of radiation therapy (conditions rendering patients hypersensitive to ionizing radiation, or unable to undergo treatment)

• Able and willing to complete the Skindex 16 and Skin Cancer Index (must be able to understand English or Spanish)

Exclusion Criteria:

• Medical contraindication to radiation therapy in the opinion of the investigator
• Prior cancer radiotherapy which precludes the ability to safely deliver radiation therapy in the opinion of the investigator
• High likelihood of protocol non-compliance in the opinion of the investigator °Patients who demonstrate unwillingness to undergo protocol-defined treatment or follow-up procedures will be ineligible to participate

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.