Justin F. Gainor, MD
Medical Oncology Physician · Boston, MA
Justin F. Gainor, MD is a medical oncology physician with a practice address in Boston, Massachusetts, and NPI 1487813010, issued on Jun 9, 2008. Check the license (Massachusetts 245561, as entered in NPPES) on the Massachusetts Board of Registration in Medicine; the Medicare figures below come from public CMS files.
- Name
- Justin F. Gainor
- Credential
- MD
- Primary taxonomy
- Medical Oncology Physician 207RX0202X
- License numbers
- 245561 MA
L-236372 MA
Self-reported in NPPES; status is on the state search - Practice location
- Massachusetts General Hospital, Boston, MA 02114
- Phone
- (617) 726-2862
- Enumerated
- Jun 9, 2008
- Record last updated
- Jul 29, 2013 (not updated in 13 years: call before relying on the address or phone)
- Medicare enrollment
- Enrolled (PECOS I20130925000694); accepts Medicare assignment
- Medical or professional school
- Harvard Medical School, 2008
- Telehealth
- Offers telehealth (CMS)
- Entity
- Type 1 · individual
8 nearest medical oncology physician records → All 421 in Massachusetts → Look up another NPI →
Also registered at Massachusetts General Hospital
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Justin F. Gainor in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMassachusetts Board of Registration in Medicine
Search for license 245561Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
73% fewer Medicare Part D claims than the average medical oncology physician in 2024
190 Medicare Part D claims for 45 beneficiaries, against an average of 703 among the 4,230 providers of this specialty who prescribed in Part D. Brand-name drugs were 32% of claims. 15 claims were for opioids.
Most prescribed
- Dexamethasone13 claims
- Zykadia13 claims
- Tabrecta12 claims
- Oxycodone Hcl11 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Industry payments in 2024: $55,687.61
43 payments; by number, the most common kind was food and beverage; the largest payer was Pfizer Inc. The 3,343 providers of this specialty with any payment received $11,773.47 on average. Payments are reported by manufacturers, not by the provider, and are not a sign of wrongdoing.
Source: CMS Open Payments, program year 2024 (openpaymentsdata.cms.gov); average among providers of this specialty with at least one payment.
Bills Medicare through 3 group practices
- Brigham And Womens Physicians Organization IncBoston, MA
- Massachusetts General Physicians Organization IncBoston, MA
- The General Hospital CorporationBoston, MA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Justin F. Gainor among 421 medical oncology physician records in Massachusetts
Justin F. Gainor, MD is one of 421 medical oncology physician records with a practice address in Massachusetts. 76% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2008, is newer than 51% of them.
- NPI issued2008 · 51% of these records are older, 43% newer
- In a Medicare fileYes · 76% of these records are
- In the CMS Doctors and Clinicians fileYes · 69% of these records are
- Graduated2008 · median 2007 among the 291 with a school on file
- Record last updated2013 · 51% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RX0202X and a Massachusetts practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Medical Oncology Physician providers in Massachusetts
There are 421 medical oncology physician records in Massachusetts.
All 421 in Massachusetts → Every provider in Boston → Medical Oncology Physician nationwide →
The 8 medical oncology physician records with the nearest ZIP codes
- Eyal Attar, MDBoston, MA 021141407847965
- Lawrence Blaszkowsky, MDBoston, MA 021141225028137
- Leif Ellisen, MD PHDBoston, MA 021141225028533
- Rajesh Gandhi, MDBoston, MA 021141992795512
- Ephraim Hochberg, MDBoston, MA 021141326038407
- Richard Lee, MD PHDBoston, MA 021141871583096
- Geoffrey Liu, MDBoston, MA 021141215928452
- Marc Michaelson, MD PHDBoston, MA 021141275523490
Common questions
What is Justin F. Gainor, MD's NPI number?
Justin F. Gainor, MD's National Provider Identifier (NPI) is 1487813010, issued on Jun 9, 2008. An NPI identifies a provider in billing; it is not a license.
Where is Justin F. Gainor, MD located?
The NPPES record lists a practice address at Massachusetts General Hospital, Boston, MA, 02114. Phone: (617) 726-2862. Providers update this record themselves, so call before visiting.
How can I verify Justin F. Gainor, MD's license?
NPPES lists Massachusetts license number 245561, as entered by the provider. Search the Massachusetts Board of Registration in Medicine at https://findmydoctor.mass.gov/. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Justin F. Gainor, MD prescribe under Medicare Part D?
In 2024, Justin F. Gainor, MD had 190 Medicare Part D claims for 45 beneficiaries; the average among medical oncology physician prescribers was 703. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.