Relationship of margin status and radiation dose to recurrence in post-operative vulvar carcinoma

To evaluate the effect of margin status and radiation dose in patients treated with radiation therapy (RT) for vulvar cancer. Clinical outcomes included vulvar recurrence (VR), relapse-free survival (RFS) and overall survival (OS).

We retrospectively reviewed the records of 300 patients with Stage I-IVA vulvar cancer treated between 1988 and 2009. Slides were reviewed and margin status was scored as negative (≥ 1 cm), close (<1cm) or positive after formalin fixation. Cox proportional hazards models were constructed to determine significant prognostic factors for vulvar relapse.

Of 205 eligible patients, 69 (34%) had negative surgical margins, 116 (56%) had close margins and 20 (10%) had positive margins. Median follow-up time was 49 months. The 4-year RFS rate was 53% and OS was 73%. Of 78 recurrences, 62 had the vulva as the first site of recurrence. The 4-year rates of freedom from vulvar recurrence were 82%, 63% and 37% for those with negative, close and positive margins, respectively (p for trend=0.005). On multivariate analysis, close margins (HR=3.03, 95% CI 1.46-6.26) and positive margins (HR=7.02, 95% CI 2.66-18.54) were associated with a significantly increased risk of vulvar relapse. Those who received a dose ≥ 56 Gy had a lower risk of relapse than those who received ≤ 50.4 Gy (p<0.05). Though recurrences were noted with margins up to 9 mm, the highest risk of vulvar recurrence was associated with margins ≤ 5 mm (p=0.002).

Close or positive margins were associated with a significantly increased risk of vulvar recurrence. Radiation with a dose ≥ 56 Gy may decrease the risk of vulvar recurrence.