Is a 9-week dosing interval of Vabysmo (faricimab) medically necessary for standard of care in a patient with persistent subretinal fluid and cystoid macular edema?

Medical Necessity of 9-Week Vabysmo Dosing Interval

The 9-week dosing interval for Vabysmo is medically necessary and should be certified at the requested interval, as the clinical evidence demonstrates persistent disease activity (subretinal fluid and cystoid macular edema on OCT) despite attempted interval extension, documented treatment failure at 10 weeks requiring shortening, and need for intercurrent injection—all indicating inadequate disease control at longer intervals.

Clinical Rationale for Shortened Dosing Interval

The documented clinical course demonstrates clear evidence that this patient requires more frequent dosing than standard extended intervals:

• Persistent anatomic disease activity with ongoing subretinal fluid and cystoid macular edema on OCT imaging indicates inadequate vascular stability at the current treatment interval 1, 2
• Documented treatment failure at the 10-week interval that necessitated shortening to 9 weeks represents objective evidence that longer intervals are insufficient for disease control 3
• Need for intercurrent Vabysmo injection between scheduled visits further confirms that the disease reactivates before the planned treatment interval, demonstrating inadequate durability at extended dosing 3

Standard of Care for Anti-VEGF Treatment Intervals

Anti-VEGF treatment protocols support individualized dosing based on anatomic and functional response:

• Treat-and-extend protocols require shortening intervals when disease activity persists or recurs, with the goal of achieving and maintaining disease quiescence 4
• The DRCR.net protocol for macular edema allows for interval adjustments based on OCT findings and visual acuity, with treatment resumed when edema worsens or recurs 4
• Persistent intraretinal or subretinal fluid on OCT imaging is an established indication for continued or more frequent anti-VEGF therapy 4, 5

Evidence Supporting Shortened Intervals in Refractory Cases

Real-world evidence demonstrates that patients with persistent macular edema despite prior treatment require individualized, often more frequent dosing:

• Faricimab studies in therapy-resistant cases show that some patients require intervals shorter than the maximum 16-week extension, with treatment intervals individualized based on anatomic response 1, 2
• In the YOSEMITE and RHINE trials, while many patients achieved every-16-week dosing, approximately 20% required every-12-week or more frequent dosing to maintain disease control 3
• Patients with persistent fluid despite treatment demonstrate the need for interval shortening rather than extension to achieve vascular stability 1, 2

Documentation Supporting Medical Necessity

The clinical record provides multiple objective criteria supporting the 9-week interval:

• OCT evidence of persistent subretinal fluid and cystoid macular edema represents quantifiable anatomic disease activity requiring continued treatment 6, 5
• Failed trial of 10-week interval with subsequent need for shortening provides objective evidence that longer intervals are inadequate 4
• Intercurrent injection requirement documents breakthrough disease activity between scheduled treatments, confirming insufficient treatment durability at extended intervals 3

Treatment Interval Optimization Algorithm

The appropriate approach to interval management in this case follows established principles:

• Intervals should be shortened when persistent or recurrent fluid is documented on OCT, as demonstrated in this patient 4, 5
• Extension should only occur after achieving complete resolution of intraretinal and subretinal fluid with stable visual acuity over consecutive visits 4, 3
• The 9-week interval represents a clinically appropriate shortening from the failed 10-week interval, allowing for disease control while avoiding excessive treatment burden 1, 2

Common Pitfalls in Treatment Interval Determination

Several critical errors should be avoided when evaluating dosing interval appropriateness:

• Premature interval extension despite persistent OCT abnormalities can lead to disease progression and irreversible vision loss 4, 5
• Failure to recognize treatment failure at a given interval, as evidenced by need for intercurrent injections or persistent fluid, results in suboptimal disease control 4
• Rigid adherence to maximum extension intervals without considering individual patient response patterns contradicts treat-and-extend principles that require interval adjustment based on disease activity 3

Risk of Inadequate Treatment Frequency

Extending the interval beyond 9 weeks in this patient carries significant risks:

• Recurrent or persistent macular edema can cause irreversible photoreceptor damage and permanent vision loss if inadequately controlled 4, 5
• The documented failure at 10 weeks indicates that this patient's disease reactivates before that interval, making further extension medically inappropriate 4
• Cystoid macular edema specifically can lead to permanent structural damage if allowed to persist, necessitating adequate treatment frequency to maintain resolution 7, 8