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Adjuvant radiation therapy provided superior local control in desmoplastic melanoma
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Data from two recent studies published in Cancer indicated adjuvant radiation therapy appeared to provide superior local control in patients with desmoplastic melanoma.
In the first study, a team of researchers led by B. Ashleigh Guadagnolo, MD, MPH, of the division of radiation oncology at The University of Texas MD Anderson Cancer Center, examined the outcomes of adjuvant radiotherapy in 130 patients (median age, 66 years) with nonmetastatic desmoplastic melanoma between 1985 and 2009.
Patients were treated with either surgery alone (n=59) or surgery plus postoperative radiotherapy (n=71). Median follow-up was 6.6 years.
Sixty-two percent of patients had a primary tumor located in the head and neck region, and 4% of patients had lymph node involvement at the time of presentation.
The OS rate was 69% at 5 years and 53% at 10 years. Disease-specific survival rates were 84% at 5 years and 80% at 10 years.
At 5 or more years, the actuarial rate of local recurrence was 17%. Local recurrence was observed in 24% of patients who underwent surgery alone compared with 7% of those who underwent surgery plus postoperative radiotherapy. Cox multivariate regression analysis showed receipt of postoperative therapy was significantly associated with improved local control(P=.009).
In the second study, Tobin Strom, MD, of the department of radiation oncology at Moffitt Cancer Center, and colleagues hypothesized that adjuvant radiotherapy would improve local control in patients with desmoplastic melanoma. Specifically, they speculated that there would be at least a 10% absolute decrease in the local recurrence rate.
The cohort included 277 patients treated for nonmetastatic desmoplastic melanoma by surgery with or without adjuvant radiotherapy between 1989 and 2010. Of these patients, 40.8% received adjuvant radiotherapy. Median follow-up was 43.1 months.
Multivariable analysis showed adjuvant radiotherapy was independently associated with improved local control (HR=0.15; 95% CI, 0.06-0.39).
There were 35 patients who experienced positive resection margins. Of them, 54% of patients who were not treated with adjuvant radiotherapy developed a local recurrence compared with 14% of those who did receive radiotherapy (P=.09).
Moreover, patients who had negative resection margins and traditionally high-risk features — such as head and neck tumor location, Breslow depth >4 mm or a Clark level V tumor — experienced significant improvements in local control (P<.05).
Therefore, the researchers suggest that patients who would be good candidates for omitting radiotherapy include those with negative resection margins, a Breslow depth ≤4 mm, and either no perineural invasion present or a non-head and neck tumor location.
“Patients with positive resection margins or deeper tumors appeared to benefit the most from radiotherapy, whereas selected low-risk patients can safely omit radiotherapy,” the researchers wrote.
For more information:
- Guadagnolo BA. Cancer. 2013;doi:10.1002/cncr.28415.
- Strom T. Cancer. 2013;doi:10.1002/cncr.28412.
Disclosure: See the full studies for lists of the researchers’ relevant financial disclosures.
Perspective
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Leslie Ballas, MD
This is a retrospective review of patients with desmoplastic melanoma who were treated from 1989 to 2010 with or without radiation. The study aimed to assess outcomes in terms of local control and local regional control, as well as histopathologic data that can help direct treatment decision-making. The study reports that adjuvant radiation therapy (RT) improves local control on multivariable analysis. At 5 years, the difference in actuarial local control was 95% in those treated with RT compared with 76% in the unirradiated population. Subgroup analysis found that positive margins were the single greatest risk factor affecting local recurrence. The addition of RT to patients who had positive margins at the time of surgery decreased local recurrence by 40 percentage points, from a local recurrence rate of 54% without RT to 14% with RT.
Other high-risk features that affect local recurrence in the negative margin patient include head and neck tumor location, Breslow depth >4mm or a Clark level V tumor.
Because the data was collected over 21 years, the study examines a heterogeneously treated population. This is seen in radiation fractionation changes, treatment planning and pathologic evaluation variations over this time frame. Regardless, the benefit of adjuvant radiation to the primary site led to statistically significant better local control in all patients. This study adds to our knowledge of the benefits of adjuvant radiation in desmoplastic melanoma and provides strong support for radiation therapy utilization after resection with positive margins.
One thing that is highlighted, but not directly addressed, is how important a negative margin is at the time of resection. Because the addition of adjuvant radiation to the primary site in the setting of a positive margin leads to a local recurrence rate of 14%, I would encourage re-resection to a negative margin whenever feasible. Based on this study, as well as others, the clinical indications for adjuvant radiation to the primary site in desmoplastic melanoma include positive margins where re-resection is not feasible, disease in the head and neck location, locally recurrent disease and thick or ulcerated lesions.
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