Radiation Oncology: A Question-Based Review


Steven H. Lin and Roland Engel

image Background

What is the incidence of melanoma in the U.S.?

~70,000 cases/yr of melanoma in the U.S. (and rising)

What are some risk factors for developing melanoma?

UV RT, fair complexion, light hair/eyes, numerous benign nevi or larger atypical nevi (>5 mm, variable pigmentation, asymmetric, indistinct borders), personal Hx of melanoma (900 times), family Hx of melanoma, and polyvinyl chloride exposure

In terms of UV exposure, what is the most important risk factor associated with development of melanoma?

Intermittent intense exposure to UVA and UVB, such as Hx of blistering burns in childhood, is the most important risk factor for developing melanoma.

What are the gender differences in terms of body distribution of melanoma lesions?

1.     Males: lesions predominantly on trunk (e.g., upper back)

2.     Females: lesions predominantly on extremities

What % of melanomas derive from melanocytic nevi?

~15% of melanomas derive from melanocytic nevi.

What % of melanomas are derived from noncutaneous sites?

<10% of melanomas are from noncutaneous sites.

What are the common noncutaneous melanoma sites?

The GI, ocular, and gyn areas are the most common noncutaneous sites.

What % of melanoma pts have LN involvement at Dx, and how does this differ by T stage?

15% of pts have LN involvement at Dx, with 5% being T1 and 25% being ≥T2.

What % of melanoma pts present with DM at Dx?

5% of pts present with DM at Dx.

What proportion of DM pts present with DM from an unknown melanoma primary?

One third of DM pts or 1%–2% of all pts present with mets from an unknown primary.

What are the 5 subtypes of melanoma?

Superficial spreading, nodular, lentigo maligna, acral lentiginous, and desmoplastic variant

Which of the 5 melanoma subtypes is the most common?

Superficial spreading (70%) is the most common subtype → nodular (25%).

What are typical features of desmoplastic melanoma?

Features of the desmoplastic subtype include older pts (60–70 yo), more infiltrative, higher rate of perineural invasion, higher LF rates, and lower nodal met/DM rates.

Which melanoma subtype has the best prognosis?

Lentigo maligna melanoma has the best prognosis.

What is the LN+ rate and 5-yr OS for lentigo maligna melanoma?

For lentigo maligna melanoma, the LN + rate is only 10%, with 5-yr OS at 85% after WLE alone.

What subtype commonly presents in dark-skinned populations, and what body locations does it commonly affect?

Acral lentiginous, which commonly affects the palms/soles and subungual areas, is the most common melanoma subtype in dark-skinned populations.

Which subtype of melanoma is most common and has the worst prognosis?

Superficial spreading is the most common subtype. This subtype also has the worst prognosis.

What is the name for lentigo maligna involving only the epidermis (Clark level I)?

Hutchinson freckle is lentigo maligna of the −epidermis.

What are 3 commonly used immunohistochemical stains for melanoma?

S100, HNB-45, and Melan-A stains are commonly used for melanoma.

image Workup/Staging

A pt presents with a pigmented lesion. What in the Hx can help to determine if this is a suspicious lesion?

Changes in ABCDE: Asymmetry, Borders, Color, Diameter (>6 mm), and Enlargement

What workup is necessary for tumors >1 mm thick?

For tumors >1 mm thick, provide a complete metastatic workup with CXR, LFTs, and CBC/CMP. CT C/A/P is needed for lesions >1 mm thick.

Per the latest NCCN guidelines, for what melanoma pts should imaging be performed?

Per the NCCN, imaging should be performed for −specific signs/Sx or stage ≥IIB (not recommended for stages IA, IB, and IIA).

What is the typical workup for small (<1-mm) melanoma lesions?

The workup is the same as for other skin cancers: H&P, CN exam (if H&N), regional LN exam, CT/MRI for extent/bone involvement, and tissue Bx.

What are some common DM sites for melanoma?

The skin, SQ tissues, distant LNs, lung, liver, −viscera, and brain are common melanoma DM sites.

What is the preferred method of tissue Dx for a suspected melanoma?

For suspected melanoma, full-thickness or excisional Bx (elliptical/punch) with a 1–3-mm margin is preferred for tissue Dx.

Why should wider margins on excisional Dx be avoided?

Avoid wide margins to permit accurate subsequent lymphatic mapping.

For what locations is full-thickness incisional or punch Bx adequate?

Full-thickness incisional and punch Bx are adequate for the palms/soles, digits, face, and ears or for very large lesions.

When is a shave Bx sufficient?

Shave Bx is sufficient when the index of suspicion for melanoma is low.

How do the Breslow thickness levels correspond to the latest AJCC T staging for melanoma?

The Breslow thickness levels are identical to and define the AJCC T staging of malignant melanoma:

1.     T1: ≤1 mm

2.     T1a: mitotic rate <1/mm2

3.     T1b: mitotic rate ≥1/mm2

4.     T2: 1.01–2 mm

5.     T3: 2.01–4 mm

6.     T4: >4 mm

7.     T4a: no ulceration

8.     T4b: ulceration

What is considered N1, N2, and N3 in melanoma staging?

All regional LN mets:

1.     N1: 1+

2.     N2: 2–3+

3.     N3: ≥4+, or matted, or in-transit mets with mets to regional node(s)

For melanoma nodal groups, into what further categories are N1-N2 stages broken?

1.     N1a: micromets

2.     N1b: macromets

3.     N2a: micromets

4.     N2b: macromets

5.     N2c: satellite or in-transit mets without nodal mets

How do M1a, M1b, and M1c differ in a pt with metastatic melanoma?

1.     M1a: skin, SQ, distant LNs

2.     M1b: lung only

3.     M1c: viscera or other sites with ↑ LDH

Describe the overall stage groupings per the latest AJCC classification.

1.     Stage 0: Tis

2.     Stage IA: T1aN0

3.     Stage IB: T2aN0 or T1bN0

4.     Stage IIA: T3aN0 or T2bN0

5.     Stage IIB: T4aN0 or T3bN0

6.     Stage IIC: T4bN0

7.     Stage III: any N+

8.     Stage IV: any M1

With regard to the pathologic staging of melanoma, how does regional nodal involvement figure into stage IIIA, IIIB, and IIIC Dz?

1.     Stage IIIA: nonulcerative primary with LN micromets

2.     Stage IIIB: ulcerative primary + LN micromets or nonulcerative primary + LN macromets/in-transit mets

3.     Stage IIIC: ulcerative primary + LN macromets/in-transit mets or N3 Dz

What are the Clark levels? Under what circumstance does the Clark level need to be known on the pathology report for a pt with melanoma?

Clark levels:

1.     Level I: epidermis only

2.     Level II: invasion of papillary dermis

3.     Level III: filling papillary dermis, compressing reticular dermis

4.     Level IV: invading reticular dermis

5.     Level V: SQ tissue

The Clark level should be provided on the pathology report for lesions ≤1 mm.

What are the similarities and differences between clinical and pathologic staging for melanomatous lesions?

Both require microstaging of the primary after resection:

1.     Clinical staging: clinical exam + radiology allowed (after complete resection)

2.     Pathologic staging: pathology assessment of LN after dissection

What should the pathology report reveal about the primary tumor in a pt with a newly diagnosed melanoma after surgical resection?

The pathology report should list the Breslow −thickness, ulceration status, mitotic rate, deep/peripheral margins, evidence of satellitosis, and Clark level (only for lesions ≤1 mm).

What are some adverse features on pathology after surgical resection for a melanoma?

Adverse pathology features after surgical resection include +margins ( + deep margin), LVSI, and a mitotic rate >1/mm2.

For clinical staging purposes, what stage designates regional nodal involvement?

Stage III designates nodal involvement in melanoma staging.

What is the most powerful prognostic factor for recurrence and survival for pts with melanoma?

Sentinel LN status is the most powerful prognostic factor.

What are 3 favorable clinical factors at presentation for pts with a newly diagnosed melanoma?

Female gender, young age, and extremity location are all favorable prognostic factors.

What are 5 poor prognostic factors on pathology in melanoma?

Increasing thickness, # of nodes involved, −ulceration, Clark level (if <1 mm), and satellitosis are 5 poor prognostic factors in melanoma.

What are microsatellites as seen with melanoma?

With melanoma, microsatellites are discrete nest of cells >0.05 mm that are separated from the body of the primary lesion by collagen or fat.

In order of frequency, which melanoma sites have the highest LR rates after surgery?

Melanoma sites with highest LR rates after surgery (in descending order of frequency): H&N (9.4%) > distal extremities (5%) > trunk (3%) > proximal extremities (1%) (Balch CM et al., Ann Surg Oncol 2001)

What are the comparative OS rates of melanoma pts by stage at presentation?

OS rates of melanoma pts by stage:

1.     Stage I: 80%–90%

2.     Stage II: 40%–60%

3.     Stage III: 30%

4.     Stage IV: <10%

image Treatment/Prognosis

What is the general paradigm for the management of melanoma lesions?

Melanoma lesion management paradigm:

1.     WLE → sentinal LN Bx (if >0.6 mm thick or >0 mitotic rate).

2.     If sentinal LN Bx is positive, then full LND is required.

When is WLE alone adequate as Tx of melanoma?

WLE alone is adequate for in situ or stage IA lesions without adverse features on Bx.

When should sentinel LN Bx be considered or recommended with WLE for melanoma?

Sentinel LN Bx with WLE for melanoma should be considered/recommended for stage IA with adverse features, stage ≥IB, or Clark 4–5.

What evidence demonstrates improved survival outcomes for prophylactic LND in the management of melanoma?

For lesions >1.6 mm thick, retrospective data by Milton et al. (Br J Surg 1982) and Urist et al. (Ann Surg 1984) have demonstrated improved survival.

A randomized study by Balch et al. (Ann Surg Oncol 2000) has shown improved survival for pts with nonulcerated lesions, lesions 1–2 mm thick, and limb lesions.

What is the LN recurrence rate for pN+ melanoma pts after LND?

After LND, the LN recurrence rate for pN+ pts is 30% at 10 yrs (Lee RJ et al., IJROBP 2000: no adj RT; 45% rcv chemo).

What min surgical margins are required by T stage for the optimal surgical management of melanoma?

Min surgical margins for optical surgical management:

1.     Tis: 5 mm

2.     T1: 1 cm

3.     T2: 1–2 cm

4.     T3-T4: 2 cm

Which randomized trials support the surgical margins currently used in the management of melanoma?

Balch et al. (Ann Surg Oncol 2001): 2 cm vs. 4 cm for >T2; no difference in outcome

Thomas et al. (NEJM 2004): 1 cm vs. 3 cm; 3 cm resulted in better LC for >T2 lesions, but no OS benefit

When is elective iliac or obturator LND necessary after resection of a lower extremity melanoma?

Elective iliac or obturator LND is necessary if there are clinically positive superficial nodes, ≥3 −superficial + LNs, or if pelvic CT shows LAD.

When is primary RT ever indicated for Tx of melanoma?

Primary RT is indicated for medically inoperable pts or lentigo maligna of the face (cosmetic outcome better); this is given as 50 Gy/20 fx or 7–9 Gy × 6 biweekly (Farshad A et al., Br J Dermatol 2002), 1.5-cm margin, 100–250 kV photons.

If primary RT is used for medically inoperable pts, what modality can be added to improve the efficacy of RT?

Hyperthermia (Overgaard J et al., Lancet 1995) improves LC (46% vs. 28%) without added toxicity.

How were RT and hyperthermia administered to pts with melanoma in the Overgaard study?

In the Overgaard study, pts were given 24 or 27 Gy in 3 fx over 8 days +/− hyperthermia (43°C × 60 −minutes), which improved LC.

When is adj RT indicated for resected melanoma?

Adj RT indications for resected melanoma:

1.     Primary site: +/close margins, desmoplastic histology

2.     Nodal site: >3 +LNs or matted LNs, >3 cm, +ECE, or incomplete nodal assessment

Note: Per the latest NCCN guidelines, consider RT for stage III pts.

Which studies suggest that RT can make up for lack of formal neck dissection in H&N pts?

1.     MDACC data by Ballo et al. (Head Neck 2005): cN+ in neck s/p local excision only with adj RT; 5-yr LC 93%

2.     Ang et al. (IJROBP 1994): high-risk pts +/− LND; 5-yr LC 88%

Note: The ongoing Australia/TROG trial is addressing this issue.

What is the only proven adj systemic therapy that improves DFS and OS in pts with resected high-risk stage III melanoma?

High-dose IFN-α, using the Kirkwood schedule (20 mU/m2/day intravenously, 5 to 7 days/wk for 4 wks → 10 mU/m2/day SQ, 3 × wk for 48 wks). However, NCCTG 83-7052 did not demonstrate benefit of IFN (costly Tx at $50–$60K/pt).

When is high-dose IFN indicated for the management of melanoma? Which studies have demonstrated a benefit for these select pts?

High-dose IFN is indicated for >4-mm or Nlesions. The ECOG 1684, 1690, and 1694 studies have shown a 10% improvement in RFS, with an OS benefit in 2 of 3 trials.

Which study showed no benefit with moderate doses of IFN after surgical resection of melanoma?

EORTC 18952 (Eggermont AM et al., Lancet 2005): stage IIb–III, randomized to 13 mos or 25 mos of IFN or observation. There was no SS difference in OS; however, there was an SS difference in DMFS with 25 mos of INF.

What is the role of combining IFN with RT as adj Tx for high-risk resected stage III malignant melanomas?

Preclinical studies demonstrate radiosensitization with IFN. Retrospective reviews demonstrate feasibility but possible increased subacute/late toxicity (see Toxicity section below). Generally, 1 mo of high-dose induction INF → RT with an intermediate maintenance dose of INF is feasible.

What RT fractionation scheme is commonly used in the adj setting for melanoma of the H&N?

Biweekly 6 Gy/fx × 5 (30 Gy) based on the Ang et al. study (MDACC data): 5-yr LRC was 88%, OS was 47%, and there was min acute/late toxicity. (IJROBP 1994)

Is there a benefit to hypofractionating RT for melanoma in the adj setting?

NoRTOG 8305 (Sause WT et al., IJROBP 1991) showed no difference between 8 Gy × 4 and 2.5 Gy × 20.

What did the University of Florida experience/study (Chang DT et al., IJROBP 2006) demonstrate regarding adj nodal RT in pts with melanoma lesions of the H&N?

The University of Florida study showed excellent 5-yr LC (87%) and no difference between hypofractionation (6 Gy × 5 fx) and standard (60 Gy in 30 fx) dosing. The major cause of mortality was DM.

What is generally recommended for a pt with nodal recurrence after primary management for melanoma?

Recommendations for a pt with nodal recurrence after primary management include restaging, FNA or LN Bx → LND if no previous dissection → consideration for adj RT and/or INF, a clinical trial, or observation.

How is salvage RT delivered in melanoma pts with isolated axillary nodal recurrences?

After axillary LND, RT to the axilla alone is sufficient (the supraclavicular region may be omitted), using 6 Gy × 5 (30 Gy) per MDACC data (Beadle BM et al., IJROBP 2009). The 5-yr LC rate was 88%.

What are some active chemo agents currently in use for metastatic melanoma?

Temozolomide, dacarbazine, interleukin-2, Taxol, and platinum-doublet with Taxol (carboplatin or cisplatin) are currently used for metastatic melanoma.

image Toxicity

What is the rate of lymphedema when treating different LN regions with hypofractionated RT?

The rates for lymphedema are 39% for the groin, 30% for the axilla, and 11% for H&N sites. (MDACC data: Ballo MT et al., Head Neck 2005)

What is the α/β ratio of melanoma?

For melanoma, the α/β ratio is 2.5. (Overgaard J et al., Lancet 1995)

When using a hypofractionated regimen (e.g., 6 Gy × 5 [30 Gy]), at what dose does the practitioner come off the spinal cord and small bowel?

2,400 cGy is the dose tolerance of the spinal cord/small bowel when hypofractionating with 6 Gy/fx.

What are the main toxicities of concurrent IFN and RT in the adj Tx of stage III melanoma?

In stage III melanoma, the use of concurrent IFN and RT in adj Tx can cause acute skin toxicity as well as increased grade 3–4 subacute and late toxicities (fibrosis, SQ necrosis, myelitis, mucositis, pneumonitis, lymphedema). Up to 50% of pts can develop grade 3 toxicities.

What are the latest NCCN follow-up recommendations for melanoma by stage?

NCCN melanoma follow-up recommendations:

1.     Annual skin exam for life (all stages)

2.     For stages IA–IIA: H&P q3–12mos for 5 yrs, then annually; routine labs/imaging not recommended

3.     For stages IIB–IV: H&P q3–6mos for yrs 1–2, then q3–12mos for yrs 3–5, then annually; routine labs for 1st 5 yrs; consider imaging (CXR, PET/CT, annual MRI brain)