The highest-RAF patients in your panel are also your highest audit risk. Charty resolves both, on the encounter.
Cancer-coded patients carry the heaviest Medicare Advantage payment weights — and the Z85 history-of-cancer family is the single most active OIG audit focus in outpatient coding right now. Charty resolves both problems where they originate: inside the oncology encounter, while the physician is still in it.
Three reasons the math is sharper here than anywhere else in MA.
The dollars are larger per patient.
Cancer-related HCCs are among the highest-weighted categories in CMS-HCC V28. Active malignancies, metastatic disease, and treatment-related complications carry RAF weights that meaningfully exceed the average MA patient. A correctly-coded active oncology patient can represent 2x to 3x the annual MA payment of an average member. A miscoded one — typically defaulted to a Z85 history code when the patient is in fact under active treatment or surveillance — represents the gap.
The OIG is actively auditing here.
The Z85 family of "history of" cancer codes has been called out repeatedly in OIG audit advisories and Medicare contractor focus areas. The audit pattern is well known: a patient is coded with Z85.x (history of) when chart review shows active disease, active surveillance, or active treatment that should have been coded with the corresponding C-code. When the contractor pulls a sample of your Z85-coded encounters, every chart where the documentation supports active disease is a clawback.
The documentation already supports the right code.
Unlike many specialties, oncology encounters generate detailed clinical documentation as a routine matter. The pathology, the staging, the treatment plan, the response assessment, the surveillance schedule — all of it lives in the note. The gap is not documentation quality. The gap is the translation from documentation to code. Charty closes exactly that gap.
Charty handles three specific oncology coding patterns that other tools miss.
Z85 History-of-Cancer Overcoding
The pattern
Patient with history of leukemia, lymphoma, breast cancer, or another active or surveilled malignancy is coded as Z85.6, Z85.71, Z85.3, etc. — the "personal history of" codes — when chart documentation shows the patient is in fact under active treatment, active surveillance, or has not yet achieved formal remission.
Why it matters
Z85 codes are zero-weight under V28 for risk adjustment in most contexts
The OIG audit pattern targets exactly this miscoding
Every Z85 chart where the note describes active treatment is both an unbilled RAF lift and an audit liability
What Charty does
The moment a Z85 cancer history code lands on the encounter, Charty's rules engine fires a hard stop. The physician confirms the clinical status — Active, In Remission, or Surveillance — directly from the note context. Charty surfaces the appropriate active code (C91.10, C82.x, C50.x family, etc.) with the supporting note language one click away. The physician resolves in seconds. The audit trail records the clinical decision.
V24-to-V28 Cancer Code Reweighting
The pattern
Cancer codes that drove meaningful RAF weight under CMS-HCC V24 have been reweighted, recategorized, or removed under V28. Most oncology revenue cycle teams have a partial map of the changes; very few have a complete one.
Why it matters
Several solid tumor and lymphoma codes have been recategorized into different V28 HCC groups, with different weights
Some V24-eligible cancer codes are no longer assigned to any V28 HCC
Disease-interaction and disease-linking rules that boosted certain cancer-plus-comorbidity combinations under V24 have been restructured
What Charty does
Every cancer-related code that hits the encounter is validated against the current V28 model in real time. If a code has been eliminated, deweighted, or replaced under V28, Charty surfaces the change with a recommended V28-compatible alternative drawn directly from the note's clinical evidence.
E&M Complexity Validation for Oncology Encounters
The pattern
Oncology encounters routinely document substantial clinical complexity — multiple active diagnoses, prescription drug management, ordering and review of diagnostic studies, coordination of multidisciplinary care — that supports higher E&M levels than are routinely billed.
Why it matters
Habitual undercoding leaves substantial revenue unbilled
Habitual overcoding creates audit exposure
Either pattern, sustained across an oncology panel, is material
What Charty does
For every oncology encounter, Charty cross-references the documented complexity against the selected E&M level. If the level is below what the documentation supports, Charty recommends the higher level with the specific complexity elements that justify it. If above, the same — with the elements that don't support the selection. The physician sees a defensible recommendation; the encounter ships to billing already aligned.
Size the gap in your oncology panel. About thirty seconds.
The general MA calculator on the homepage assumes typical panel composition. This calculator assumes higher per-patient RAF, a Z85-concentrated audit risk distribution, and the E&M complexity profile typical of oncology encounters.
Z85 → Active Code Revenue Opportunity
$2.7M
403 estimated Z85 encounters with active-disease documentation. Avg RAF lift of 0.45 per correction.
Audit Clawback Exposure
$725,400
Estimated clawback risk on Z85-coded charts where documentation supports active disease. Based on ~$1,800 avg per chart.
E&M Undercoding Opportunity
$43,200
~25% of oncology MA encounters undercoded by one E&M level. Avg $45 per corrected encounter.
Oncology-specific estimates assume cancer-coded MA patients carry an average annual MA payment substantially above the 1.0 RAF baseline. The exact multiplier depends on disease, stage, treatment status, and comorbidity profile — Stemma's estimates use a range based on V28 HCC weights for common active cancer codes applied to the citable 2025 MA baseline payment. Actual lift will vary by panel and current coding practices. Calculator output is an order-of-magnitude estimate, not a promise of recovery.
One real-shape encounter, walked through end-to-end.
This is illustrative, not from a customer. It's intended to show the math and the workflow on a chart that resembles ones oncology service lines see every day.
The Encounter
Patient
71-year-old MA-enrolled patient, established with oncology practice for chronic lymphocytic leukemia (CLL).
Visit
Routine follow-up, 6-month surveillance interval.
What got coded
Z85.6 — Personal history of leukemia
I10 — Essential hypertension
E11.9 — Type 2 diabetes without complications
F32.9 — Major depressive disorder, unspecified
E&M billed at 99213
"Patient with CLL, currently on active hematology surveillance, no current chemotherapy. Most recent labs show stable absolute lymphocyte count… HbA1c 8.6 — diabetes uncontrolled on metformin monotherapy, adding empagliflozin today. Reports new depressed mood with sleep disruption, started sertraline two weeks ago…"
What Charty Surfaces
Hard stop — Z85.6 (Perfection Coding)
Rules EngineNote documents active hematology surveillance with current clinical management. Patient has not achieved formal remission. Supported code: C91.10 (CLL, not having achieved remission). Supporting note language surfaced one click away.
Specificity gap — E11.9
AI LayerDocumentation supports E11.65 (Type 2 diabetes with hyperglycemia). HbA1c 8.6 and active medication adjustment are explicit in the note.
Specificity gap — F32.9
AI LayerNote documents moderate depression with neurovegetative symptoms and active SSRI treatment. Supported code: F32.1 (moderate single episode).
E&M recommendation: 99214
E&M ValidationFour active diagnoses managed, two medication adjustments, prescription drug management for a high-complexity condition. Complexity supports 99214; 99213 selection appears habitual.
The physician sees all four findings in a single sidebar. Each resolution is one click. Total time on Charty interactions for this encounter: under 90 seconds.
Inside Epic, inside the oncology encounter, before the bill goes out.
Physician opens the oncology encounter.
In Epic Hyperspace, normal workflow. No new login, no second screen.
Charty initializes in the sidebar.
Reading the active diagnoses, problem list, recent labs, current medications, treatment plan, and the documented note.
Hard stops fire in under a second.
Z85 codes flagged against active treatment evidence; eliminated V24 codes called out; cancer codes that don't match documented stage or status surfaced for review.
AI analysis completes within seconds.
Specificity gaps on comorbidities (diabetes complications, depression severity, etc.), missing diagnoses present in the note but absent from the bill, MEAT failures on chronic conditions.
E&M validation displayed.
Alongside the physician's selection — supporting complexity elements shown explicitly when an upgrade or downgrade is recommended.
Physician resolves each finding in seconds.
Accept, edit, or override with typed justification. Each action signed and timestamped.
Encounter closes correctly. Bill goes out correctly.
Eighteen months later, if the auditor arrives, the entire encounter reconstructs in seconds from the audit log.
Two oncology environments. Same problem. Same solution.
Hospital-Owned Cancer Service Lines
You operate a multi-physician oncology service line within a larger health system. Your revenue cycle leadership is asking why MA reimbursement isn't tracking with patient acuity. Your compliance team is watching the OIG advisories on Z85 audits. Your CMIO is hearing that the EMR's built-in coding tools aren't catching the V28 changes.
Charty deploys against your existing Epic instance, scoped to one or two oncology clinics initially, with measurement built in.
Independent Community Oncology Practices
You run a community oncology practice — 10 to 50 physicians, independent or part of a USON/OneOncology-style network. You're under MA risk arrangements directly or through ACO participation. You don't have a 30-person retrospective CDI department; you have a small coding team trying to keep up.
Charty is sized for exactly your environment. Faster to deploy, lower configuration overhead, and the math hits the practice bottom line — not a hospital margin you don't capture.
90 days. One oncology clinic line. Defensible measurement.
We scope oncology pilots tighter than general practice pilots because the population is more homogeneous and the measurement is cleaner. A typical oncology pilot covers one clinic line — medical oncology, hematology, or a mixed onc-hem practice — for 90 days.
Weeks 1–2
Setup
Epic SMART-on-FHIR registration against your sandbox, rules engine configuration against your active oncology codes
Baseline measurement of current Z85/active-code ratio and current E&M distribution
Physician onboarding (typically 30 minutes per provider)
Weeks 3–10
Active Pilot
Charty live in the workflow
Weekly check-ins with the oncology medical director, revenue cycle, and compliance
Real-time dashboard: compliance scores, hard stops resolved, RAF impact estimate, E&M distribution shift, physician acceptance rates
Weeks 11–13
Measurement
Audit-defensible report comparing pilot clinic against your baseline and a matched control clinic if available
Z85-to-active code conversion rate, E&M distribution shift, RAF lift estimate (full math shown), audit-risk-reduction metrics, physician satisfaction
Pilot Commitment
You commit clinic time. You receive a complete picture of where your oncology coding is leaking revenue and creating exposure, with documentation defensible enough to support your business case for full deployment — or to walk away if the math doesn't justify continuing.
Questions oncology operators tend to ask.
The math is sharpest in oncology. The pilot can be too.
A 30-minute conversation is enough to scope whether Charty for Oncology fits your service line. We'll walk through your current Z85 distribution, your V28 readiness, your E&M distribution, and what a 90-day pilot scoped to one of your clinics would look like.