Radiation Oncology/Sarcoma/DFSP

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Dermatofibrosarcoma Protuberans

Epidemiology[edit | edit source]

  • Cutaneous, locally aggressive, primarily low grade sarcoma
    • ~10% may contain a high-grade fibrosarcoma component
    • Low rate (<5%) of metastasis; higher if fibrosarcoma component
  • Rare, 2-6% of soft tissue sarcomas
  • Adults in 30's
  • Risk factors: pregnancy, arsenic exposure, acanthosis nigricans

Clinical Presentation[edit | edit source]

  • Plaque-like areas of cutaneous thickening
  • Skin-colored, red-brown, or violaceous, particularly at the margins
  • May arise within pre-existing scar or tattoo
  • As it slowly enlarges, becomes raised ("protuberans"), firm, and nodular (fixed to dermis, but moves over deeper structures)
    • At diagnosis, >75% are superficial and <5cm diameter
  • Slow, indolent growth, such that the lesion may be present for years
  • Distribution:
    • Trunk ~50%
    • Lower extremity ~20%
    • Upper extremity 15%
    • Head and neck 15%

Work Up[edit | edit source]

  • MRI helpful to estimate extent of deep extent
  • CT not routinely necessary, unless bony invasion suspected
  • Metastatic workup not routinely necessary, unless suspicion from H&P

Histology[edit | edit source]

  • Cell of origina is not well understood
    • Histochemistry and electron microscopy suggest fibroblast lineage
    • However, the cells are CD34 positive, suggesting possibly dendritic lineage
    • In comparison, dermatofibromas and desmoid tumors are CD34-
  • The tumors show benign-appearing spindle cells, in an irregular patterns resembling a straw mat. In early lesions there is a tumor-free zone with epidermis
  • >90% have a t(17;22) translocation, resulting in a fusion of PDFG-B driven by a highly expressed collagen promoter (COL1A1)
    • Results in PDFGRb activation, which is tyrosine kinase receptor

Staging[edit | edit source]

  • American Musculoskeletal Tumor Society Staging for DFSP
    • Stage IA - Low or intermediate grade within the subcutaneous compartment
    • Stage IB - Low or intermediate grade extending outside anatomic compartment
    • Stage II - High grade histology

Natural History[edit | edit source]

  • Tends to recur locally after excision alone
  • Recur locally multiple times before metastasis; significant interval before development of metastases.
  • Fibrosarcomatous changes predict for metastatic potential.

Treatment Overview[edit | edit source]

  • Surgical resection is the primary treatment approach
    • Historically, wide local excision with 3cm margins was recommended, down to and including fascia
    • Mohs mapping reveals fine tentacles of tumor, and is becoming favored due to preservation of cosmesis
    • Some recommend modified Mohs to include a final path margin for permanent section
    • Pooled local recurrence rate with adequate margin WLE or Mohs' is <2%
    • Recurrences tend to occur within 3 years of surgery
  • Definitive RT not routinely; only couple reports available
  • Adjuvant radiation is typically indicated if positive or close margins, further resection anatomically not possible if recurrence happens, or recurrent disease
  • Given the high rate of t(17;22) leading downstream to a tyrosine kinase activation, efforts are under way to use Gleevec and other TKIs in this disease

Adjuvant Radiation Therapy[edit | edit source]

  • MD Anderson
    • 2013 (1972-2010) PMID 23628134 -- Dermatofibrosarcoma Protuberans: Long-term Outcomes of 53 Patients Treated With Conservative Surgery and Radiation Therapy. (Castle KO, Int J Radiat Oncol Biol Phys. 2013 Jul 1;86(3):585-90. doi: 10.1016/j.ijrobp.2013.02.024. Epub 2013 Apr 26.)
      • Retrospective. 53 consecutive patients. Surgery and preoperative (13%) or postoperative (87%) RT. Median tumor size 4 cm (1-25 cm). Preop dose 50 Gy, postop dose 60-66 Gy. Gross disease 7%, positive margin 30%. Median F/U 6.5 years
      • Outcome: Recurrence 4%. 5-year and 10-year OS 98%. Fibrosarcomatous change not associated with risk of LR or DM
      • Toxicity: 13%; moderate/severe complications 9% at 10 years
      • Conclusion: DFSP is radioresponse with excellent local control after surgery and RT. Adjuvant RT should be considered if large/recurrent tumor or where attempt at wide surgical margins would result in significant morbidity
    • 1998 PMID 9531366 -- "The role of radiation therapy in the management of dermatofibrosarcoma protuberans." (Ball MT, Int J Radiat Oncol Biol Phys. 1998 Mar 1;40(4):823-7.
      • Retrospective. 19 patients receiving adjuvant xrt. 60 Gy given for +microscopic margin; 65 Gy given for gross residual disease. Local control at 10 yrs was 95%
      • Conclusion: adjuvant xrt should be considered for +margins or if adequate wide excision would lead to major cosmetic defect.
  • Soft Tissue Tumours Working Group, The Netherlands Cancer Institute; 1997 PMID 9376187 -- Haas RL et al. "The role of radiotherapy in the local management of dermatofibrosarcoma protuberans."
    • 38 consecutive pts w/ DFSP. 21 tx'd surgically, 17 tx'd w/ combined modality.
    • Surgery alone had local control of 67%
    • Combined modality had local control of 82% (many of these who had xrt already had multiple local recurrences.
  • Harvard; 1996 PMID 8708729 -- Suit H et al. "Radiation in management of patients with dermatofibrosarcoma protuberans." J Clin Oncol. 1996 Aug;14(8):2365-9.
    • 18 patients treated with postop (n=15) or definitive (n=3) xrt. Population was +/close margins or xrt alone.
    • Local control at 10yrs was 88%.